THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by James

The impulse to believe the absurd when presented with the unknowable is called religion. Whether this is wise or unwise is the domain of doctrine. Once you understand someone's doctrine, you understand their rationale for believing the absurd. At that point, it may no longer seem absurd. You can get to both sides of this conondrum from here.

THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by James

Postby admin » Fri Oct 09, 2015 8:13 pm

THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH
by James Lovelock
©1988 by The Commonwealth Fund Book Program of Memorial Sloan-Kettering Cancer Center
Jacket design by Kevin O'Neill

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Table of Contents:

• Inside and Back Cover
• Foreword
• Preface
• 1: Introductory
• 2: What is Gaia?
• 3: Exploring Daisyworld
• 4: The Archean
• 5: The Middle Ages
• 6: Modern Times
• 7: Gaia and the Contemporary Environment
• 8: The Second Home
• 9: God and Gaia
• Epilog
• References
• Further Reading
• Index

Geophysiologists do not ignore the depletion of the ozone layer in the stratosphere with its concomitant risk of increased irradiation with short-wave ultraviolet, or the problem of acid rain. These are seen as real and potentially serious hazards but mainly to the people and ecosystems of the First World -- from a Gaian perspective, a region that is clearly expendable. It was buried beneath glaciers, or was icy tundra, only 10,000 years ago. As for what seems to be the greatest concern, nuclear radiation, fearful though it is to individual humans it is to Gaia a minor affair. It may seem to many readers that I am mocking those environmental scientists whose life work is concerned with these threats to human life. This is not my intention. I wish only to speak out for Gaia because there are so few who do, compared with the multitudes who speak for the people.

***

They hate to admit it, but the life scientists, whether the natural historians of the nineteenth century or the biologists of the twentieth, cannot explain what life is in scientific terms. They all know what it is, as we have done since childhood; but in my view no one has yet succeeded in defining life.

***

Life is social. It exists in communities and collectives.

***

"What is the meaning of the books?" I would have seized some of them for experimental tests -- for example, burning them in a calorimeter and measuring, accurately, the heat released.

***

I like to think of entropy as the quantity that expresses the most certain property of our present Universe: its tendency to run down, to burn out. Others see it as the direction of time's arrow, a progression inevitably from birth to death. Far from being something tragic or a cause of sorrow, this universal tendency to decay benefits us. Without the decay of the Universe there could have been no Sun, and without the superabundant consumption of its energy store the Sun could never have provided the light that let us be.

***

But imagine that some cosmic chef takes all the ingredients of the present Earth as atoms, mixes them, and lets them stand. The probability that those atoms would combine into the molecules that make up our living Earth is zero.

***

At the risk of having my membership card of the Friends of the Earth withdrawn, I say that only by pollution do we survive. We animals pollute the air with carbon dioxide, and the vegetation pollutes it with oxygen. The pollution of one is the meat of another.

***

An important general conclusion is that large and unprecedented perturbations imposed by man are likely to be more traumatic for complex ecosystems than for simple ones. This inverts the naive, if well intentioned, view that "complexity begets stability" and its accompanying moral that we should preserve, or even create, complex systems as buffers against man's importunities. I would argue that the complex natural ecosystems currently under siege in the tropics and subtropics are less able to withstand our battering than are the relatively simple temperate and boreal systems. This disclaimer recognizes the stability of complex ecosystems in the real world; but the impression remains that diversity is, in general, a disadvantage and that Nature, by disregarding the elegant mathematics of theoretical biology, has somehow cheated.

***

Perhaps it is a metaphor for our own experience that the family and society do better when firm, but justly applied, rules exist than they do with unrestricted freedom.

***

Daisyworld does not have any clearly established goal like a set point; it just settles down, like a cat, to a comfortable position and resists attempts to dislodge it.

***

It is small wonder that practitioners of the various disciplines imagine that in these imaginary worlds they see glimpses of real world whereas in fact they are lost in the fractal dimensional world of a Mandelbrot set that goes on forever at every level from minus to plus infinity. The delusion is encouraged by professional mathematicians who find similarities between their mathematical theories and the pathologies of the real world, and the numerous modern mathematical scientists whose contemplation of the demons of hyper-space -- the "strange attractors" of chaos -- is much more beguiling than the dull old real world of Nature.

***

It matters little whether Gaia theory is right or wrong; already it is providing a new and more productive view of the Earth and the other planets. Gaia theory provokes a view of the Earth where: 1. Life is a planetary-scale phenomenon. On this scale it is near immortal and has no need to reproduce. 2. There can be no partial occupation of a planet by living organisms. It would be as impermanent as half an animal. The presence of sufficient living organisms on a planet is needed for the regulation of the environment. Where there is incomplete occupation, the ineluctable forces of physical and chemical evolution would soon render it uninhabitable. 3. Our interpretation of Darwin's great vision is altered. Gaia draws attention to the fallibility of the concept of adaptation. It is no longer sufficient to say that "organisms better adapted than others are more likely to leave offspring." It is necessary to add that the growth of an organism affects its physical and chemical environment; the evolution of the species and the evolution of the rocks, therefore, are tightly coupled as a single, indivisible process. 4. Theoretical ecology is enlarged. By taking the species and their physical environment together as a single system, we can, for the first time, build ecological models that are mathematically stable and yet include large numbers of competing species. In these models increased diversity among the species leads to better regulation.

***

We have at last a reason for our instinctive anger over the heedless deletion of species; an answer to those who say it is mere sentimentality. No longer do we have to justify the preservation of the rich variety of species in natural ecosystems, like those of the humid tropical forests, on the feeble humanist grounds that they might, for example, carry plants with drugs that could cure human disease. Gaia theory makes us wonder if they offer much more than this. Through their capacity to evaporate vast volumes of water vapor through the surface of their leaves, trees serve to keep the ecosystems of the humid tropics and the planet cool by providing a sunshade of white reflecting clouds.

***

There is the wartime joke that hides a truth: how the message passed by word of mouth, "Send reinforcements, we are going to advance" mutated into "Send three and four pence, we are going to a dance." If we wish to know life's origins from genetic information we need to be prepared to reconstruct the truth from errors of this kind.

***

We tend to ignore that we oddities, who use combustion as a source of energy, inhabit a nuclear-powered Universe. The power plants, the stars, run for billions of years with utmost reliability. But just as the most dependable systems we design can still have the occasional accident, so some kinds of stars occasionally explode. Fortunately for us, one of them did and gave us the start we needed.

***

We are so used to thinking of radioactivity as artificial that we easily ignore the fact that we ourselves are naturally radioactive. Every minute, in each one of us, a few million potassium atoms undergo radioactive decay.... The element potassium is radioactive but it is also essential for life. If it were removed and replaced by the very similar element, sodium, we should die instantly. Potassium, like uranium and thorium and radium, is a long-lived radioactive nuclear waste of the supernova bomb. When potassium atoms decay, they are transmuted to form atoms of calcium and of the noble gas argon.

***

We can accept as reasonable the view that life started from the molecular chemical equivalent of eddies and whirlpools. The power that drove them was the flux of energy from the Sun and also the free energy of a hot young Earth....

The stepwise evolution from protolife to the first living cell by a process of natural selection does not seem to me so difficult an intellectual pill to swallow....

Again, the mental image of a wind instrument like a flute is helpful in this otherwise confusing topic. Just blowing makes a hiss of unruly dissipating eddies. But when the flutist blows across the port hole of the flute, the eddies are caught and tamed within the solid bounds of its hollow resonant tube to emerge as coherent musical notes.

***

I suspect that the origin of Gaia was separate from the origin of life. Gaia did not awaken until bacteria had already colonized most of the planet. Once awake, planetary life would assiduously and incessantly resist changes that might be adverse and act so to keep the planet fit for life. .

***

The successful evolution of the photosynthesizers could have led to the first environmental crisis on Earth, and I like to think the first evidence of Gaia's awakening.

***

What I would like to propose is a dynamic interaction between the early photosynthesizers, the organisms that processed their products, and the planetary environment. From this there evolved a stable self-regulating system, a system that kept the Earth's temperature constant and comfortable for life.

Before venturing further into this imaginary reconstruction of life with Gaia in the Archean, I must emphasize that it will be no more than a flight of fancy....The point of my model is not to argue for one or other global Archean ecosystem, but rather to illustrate how Gaia theory provides a different set of rules for planet models. The possible climatologies and geologies of a living planet are wholly different from those of a dead planet bearing life as a mere passenger. Having said this, let us continue with our "let's pretend."

***

Like Daisyworld, there is an abrupt change of conditions when life starts. Living organisms grow rapidly until a steady state is reached where growth and decay are in balance. This rapid, almost explosive, tendency to expand to fill an environmental niche acts as an amplifier. The system moves rapidly in positive feedback to approach a balance. Soon stability is achieved and the planet runs on in comfortable homeostasis.

***

But there would have been violent interruptions when planetesimals crashed in from space. There were at least ten of these collisions; each a catastrophe great enough to destroy more than half of all planetary life. They would have changed the physical and chemical environment enough to hazard the remainder of life for hundreds if not thousands of years to follow. It is a tribute to the strength of Gaia that our planetary home was restored so promptly and effectively after these events.

***

That, then, is an account of a few aspects of the Archean seen through Gaia theory. It was a period when the Earth's operating system was populated wholly by bacteria. It was a long period, when the living constituents of Gaia could be truly considered as a single tissue. Bacteria are both mobile and motile, and could have moved around the world carried by winds and ocean currents. They can also readily exchange information, as messages encoded on low-molecular-weight chains of nucleic acids called plasmids. All life on Earth was then linked by a slow but precise communication network. Marshall McLuhan's vision of the "global village," with humans tied in a chattering network of telecommunication, is a re-enactment of this Archean device.

***

The speculations that follow about the regulation of climate, oxygen, salinity and other properties of the environment are in this geophysiological context, in other words, as if they were speculations about the state of a living organism. In no sense is this intended as a teleology, or meant to imply that the biota use foresight or planning in the regulation of the Earth. What we need to think about is how a global regulatory system can develop from the local activity of organisms. It is by no means far-fetched to imagine a single new bacterium evolving with its environment to form a system that can change the Earth.

***

A bizarre consequence of the appearance of oxygen was the advent of the world's first nuclear reactors. Nuclear power from its inception has rarely been described publicly except in hyperbole. The impression has been given that to design and construct a nuclear reactor is a feat unique to physical science and engineering creativity. It is chastening to find that, in the Proterozoic, an unassertive community of modest bacteria built a set of nuclear reactors that ran for millions of years....Bacteria could not have debated the costs and benefits of nuclear power. The fact that the reactors ran so long and that there was more than one of them suggests that replenishment must have occurred and that the radiation and nuclear waste from the reactor was not a deterrent to that ancient bacterial ecosystem. (The distribution of stable fission products around the reactor site is also valuable evidence to suggest that the problems of nuclear waste disposal now are nowhere near so difficult or dangerous as the feverish pronouncements of the antinuclear movement would suggest.)

***

During the Proterozoic, the constant rain of planetesimals continued. As well as numerous smaller ones, there were at least ten that did damage to Gaia comparable in severity to that of a burn affecting 60 percent of the skin area of a human.

***

If we take Gaia to be a living organism, the Phanerozoic can be viewed as the most recent stage in her life, and the one she is still in. This may be easier than considering independently the lives of the billions of organisms from which she is made. Getting to know a friend does not usually require a detailed knowledge of her cellular structure. Similarly, geophysiology, concerned with the whole Earth, need not be too confused by the mass of undecomposed detail that lies, like thick layers of fallen leaves, beneath the branches of the tree of science.

***

My colleagues have made it very clear to me that what follows about oxygen is speculative and often contrary to conventional wisdom. I have included it in spite of their protest because it illustrates a view of the evolution of free oxygen in the light of Gaia theory. Whether it is right or wrong seems to me less important than its value in stimulating new experiments and measurement.

***

We seem to be approaching the end of one of these long stable periods. When life began, the Sun was less luminous and the threat was overcooling. In the middle ages of the Proterozoic, the Sun shone just right for life and little regulation was needed, but now it grows hot and overheating becomes an ever-increasing threat to the biosphere of which we are a part.

***

This vision of a blighted summer's day somehow encapsulates the conflict between the flabby good intentions of the humanist dream and the awful consequences of its near realization....There can be very few who do not in some way add to the never-ceasing demolition of the natural environment. Characteristically, arrogantly, we blame technology rather than ourselves.

***

Those simple bacteria that first used sunlight to make themselves ...

***

Looked at from the time scale of our own brief lives, environmental change must seem haphazard, even malign. From the long Gaian view, the evolution of the environment is characterized by periods of stasis punctuated by abrupt and sudden change. The environment has never been so uncomfortable as to threaten the extinction of life on Earth, but during those abrupt changes the resident species suffered catastrophe whose scale was such as to make a total nuclear war seem, by comparison, as trivial as a summer breeze is to a hurricane. We are ourselves a product of one such catastrophe. Could it be that we are unwittingly precipitating another punctuation that will alter the environment to suit our successors?

***

It is true that, in the case of Gaia, the complaint comes not from the patient but rather from the intelligent fleas that infest her.

***

For humans, a hundred thousand years is almost indistinguishable from infinity; to Gaia, who is about 3.6 eons old, it is equivalent to no more than three of our months. Gaia has cause for concern about the long-term decline of carbon dioxide, but the rise of carbon dioxide from burning fossil fuels is, for her, just a minor perturbation that lasts but an instant of time. She is, in any case, tending to offset the decline....The rate and the extent of the rise of carbon dioxide now under way as a result of our actions is comparable with that of the natural rise that terminated the last ice age. Some time in the next century it seems likely that the increment we add will be equal to that caused by the failure of the pumps some 12,000 years ago. The change of climate we need to think about, therefore, is possibly one as large as that from the last ice age until now; one that would make winter spring, spring summer, and summer always as hot as the hottest summer you can recall.

***

Some wisdom comes from geophysiology, which reminds us that the Earth is an active and responsive system and not just a damp and misty sphere of rock. Systems in homeostasis are forgiving about perturbations, and work to keep the comfortable state. Maybe, if left to herself, Gaia could absorb the excess carbon dioxide and the heat that it brings.

***

Much more serious than the direct and predictable effects of adding carbon dioxide to a stable system are the consequences of disturbing a system that is precariously balanced at the limits of stability. From control theory, and from physiology, we know that the perturbation of a system that is close to instability can lead to oscillations, chaotic change, or failure. Paradoxically, an animal close to death from exposure to cold, whose core temperature is below 25°C, will die if put into a warm bath. The well-intentioned attempt to restore heat succeeds only in warming the skin to the point where its oxygen consumption is greater than the slowly beating, still-cold heart and lungs can supply. In a vicious circle of positive feedback the blood vessels of the skin dilate; this so reduces blood pressure that death comes rapidly from the failure of the heart as a pump to circulate blood that is too depleted in oxygen for the system's needs. A hypothermic animal will recover if left to warm slowly, or if heat is supplied internally as by diathermy.

***

Like our latter-day physician, we find that diagnosis is easier than a cure. We are left with the uneasy feeling that to add carbon dioxide to the Earth now could be as unwise as warming the surface of our hypothetical hypothermic patient. It is not much comfort to know that, if we inadvertently precipitate a punctuation, life will go on in a new stable state. It is a near certainty that the new state will be less favorable for humans than the one we enjoy now.

***

A Case of Acid Indigestion: The greenhouse effect of carbon dioxide is not the only problem to arise from the burning of fossil fuels. In the northern temperate regions of the Earth there is an increased morbidity and mortality of the ecosystems. Trees, and the life in lakes and rivers, are particularly affected. The symptoms seem to be connected with an observed increase in the rate of deposition of acidic substances. Combustion is said to be the cause of acid deposition and of all the harm it does to forest ecosystems. Does geophysiology have any different view on this? It could be said that it is all the fault of oxygen. If those ancient godfathers, the cyanobacteria, had not polluted the Earth with this noxious gas there would be no oxides of nitrogen and of sulfur to trouble the air, and therefore no acid rain.

***

Any detached observer of the heated European or North American debate over acid rain might gather the impression that all acid rain was due to the burning of sulfur-rich fossil fuel in power stations, industrial furnaces, and domestic heating systems....Canada, Scandinavia, Scotland, and many other northern regions are on ancient rocks, the hard, soluble residue of eons of weathering. The ecosystems that survive on this unpromising, and often normally acidic, terrain have less capacity to resist the stress of acidification. It is from the countries of these regions that comes a justifiable complaint that their industrial neighbors are destroying them....

The geophysiological contribution to this debate is to observe that this acid indigestion may have another source in addition to the sulfuric vinegar of neighbors. The fitting of sulfur dioxide removers to the chimneys might only alleviate, not cure, the problem. The neglected source of acid is the natural sulfur carrier, dimethyl sulfide. In the past two years, Meinrat Andreae and Peter Liss (ocean chemists based, respectively, in Florida and the United Kingdom) have shown that the emission of this gas from phytoplankton blooms at the surface of the oceans around western Europe is so large as to be comparable with the total emissions of sulfur from industry in this region.

***

In the late 1960s I developed a simple apparatus able to detect chlorofluorocarbons (CFCs) in the atmosphere down to parts per trillion by volume. This is an exquisite sensitivity; at such levels even the most toxic of chemicals could be breathed in or swallowed without harm, indefinitely.

***

Ozone is a deep blue, explosive, and very poisonous gas. It is strange that so many have regarded it as if it were some beautiful endangered species. But it was the mood of the 1970s to respond to environmental hazards much as previous generations had responded to witchcraft....This was also the time when the word "chemical" became pejorative, and all products of the chemical industry were assumed to be bad unless proved harmless. In a more sensible environment, we might have regarded the predictions of doom in the next century due to a single industrial chemical as far fetched -- something to watch closely, but not something requiring immediate legislation. But the 1970s was not the time for a long, cool look at things.

***

Once again the wisdom of Paracelsus that the poison is the dose was ignored, and in its place the "zero" shibboleth took charge. "There is no safe level of ultraviolet radiation," was the cry. "Ultraviolet, like other carcinogens, should be reduced to zero." In fact, ultraviolet radiation is part of our natural environment, and has been there as long as life itself. It is the nature of living things to be opportunistic. Ultraviolet, although potentially harmful, can also be used by living organisms for the photosynthesis of vitamin D. When it is a threat, it can be avoided by synthesizing such pigments as melanin to absorb it.

***

Exposure to any radiation with a high quantum energy that penetrates the skin can damage the genetic material of our cells and corrupt their program of instructions. Among the adverse effects is the conversion from normal to malignant growth. This is frightening stuff, but we can keep our cool by remembering that these carcinogenic consequences are no different from those of breathing oxygen, which is also a carcinogen. Breathing oxygen may be what sets a limit to the life span of most animals, but not breathing it is even more rapidly lethal. There is a right level of oxygen, namely 21 percent; more or less than this can be harmful. To set a level of zero for oxygen in the interests of preventing cancer would be most unwise.

***

Ozone, they said, prevents the penetration of hard ultraviolet radiation that otherwise would keep the land sterilized and uninhabitable by life. This was a decent scientific hypothesis and a very testable one at that. Indeed it was tested by my colleague Lynn Margulis, who challenged it by showing that photosynthetic algae could survive exposure to ultraviolet radiation equivalent in intensity to that of sunlight unfiltered by the atmosphere. But this did not stop the hypothesis from becoming one of the truly great scientific myths of the century; it is almost certainly untrue, and it survives only because of the apartheid that separates the sciences.

***

The natural energy of the Universe, the power that lights the stars in the sky, is nuclear. Chemical energy, wind, and water wheels: such sources of energy are, from the viewpoint of a manager of the Universe, almost as rare as a coal-burning star. If this is so, and if God's Universe is nuclear-powered, why then are so many of us prepared to march in protest against its use to provide us with electricity?

***

[E]ven water can kill if too much is taken. It is usually assumed that the change in attitude towards radiation came from our revulsion at that first misuse of nuclear energy at Hiroshima and Nagasaki. But it is not that simple. I well remember how the first nuclear power stations were a source of national pride as they quietly delivered their benefice of energy without the vast pollution of the coal burners they replaced. There was a long spell of innocence between the end of the Second World War and the start of the protest movements of the 1960s. So what went wrong?

Nothing really went wrong, it just happens that nuclear radiation, pesticides, and ozone depleters share in common the property that they are easily measured and monitored. The attachment of a number to anything or anyone bestows a significance that previously was missing. Sometimes, as with a telephone number, it is real and valuable. But some observations -- for example, that the atmospheric abundance of perfluoromethyl cyclohexane is 5.6 x 10-15, or that as you read this line of text at least one hundred thousand of the atoms within you will have disintegrated -- while scientifically interesting, neither confer benefit nor have significance for your health. They are of no concern to the public.

***

If this alone were not enough, there are the media, ready to entertain us. They have in the nuclear industry a permanent soap opera that costs them nothing. Why, we can even experience the excitement of a real disaster, like Chernobyl, but in which, as in fiction, only a few heroes died. It is true that calculations have been made of the cancer deaths across Europe that might come from Chernobyl, but if we were consistent, we might wonder also about the cancer deaths from breathing the coal smoke smogs of London and look on a piece of coal with the same fear now reserved for uranium. How different is the fear of death from nuclear accidents from the commonplace and boring death toll of the roads, of cigarette smoking, or of mining -- which when taken together are equivalent to thousands of Chernobyls a day.

***
The foregoing paragraphs are not intended as support for the nuclear industry, nor to imply that I am enamoured of nuclear power. My concern is that the hype about it, both for and against, diverts us from the real and serious problem of living in harmony with ourselves and the rest of the biota....To my ecologist friends, many of whom have been at the sharp end of protest against nuclear power, these views must seem like a betrayal. In fact, I have never regarded nuclear radiation or nuclear power as anything other than a normal and inevitable part of the environment.

***

Let's look at his proposition: "Suppose that the biological effects of exposure to nuclear radiation are no different from those of breathing oxygen."... Or to put it another way, breathing is fifty times more dangerous than the sum total of radiation we normally receive from all sources.

***

[W]e can only guess that tropical forest systems are vital for the world ecology. It may be that they are like the temperate forests that seem to be expendable without serious harm to the system as a whole.

***

We do recognize the needs of the Earth, even if our response time is slow. We can be altruistic and selfish simultaneously in a kind of unconscious enlightened self-interest. We most certainly are not a cancer of the Earth, nor is the Earth some mechanical contraption needing the services of a mechanic.

***

I will remind you that the Gaia hypothesis was a serendipitous discovery, arising directly from the invention of a method of planetary-life detection intended for use on Mars. Nearly twenty years later I found myself speculating on the possibility of changing the physical environment of Mars so that it becomes a self-sustaining living system and a brother to Gaia. ...It came about because of a book called The Greening of Mars, written with my friend Michael Allaby, a fluent writer on environmental topics. He wanted a world on which to act out a new colonial expansion; a place with new environmental challenges and free of the tribal problems of the Earth. I just wanted a model planet on which to play new games with Gaia, or rather Ares, the proper name for Gaia's sibling.

***

To make Mars a fit home for life we shall first have to make the planet comfortable for bacterial life. In the book, we proposed that this impossible and outrageous act, the changing of the environment of a whole planet, could only be done by a slightly disreputable entrepreneur; the type of man about whom it is said, "He never breaks the law but whenever he does something, legislation is needed to stop him from doing it again." People like this are needed to probe the boundaries and to do those things that are forbidden, things that are apparently too costly or are beyond the possibility of achievement by the well-meant but sometimes undesirable caution of the planned enterprise of governmental agencies.

The scenario of The Greening of Mars included therefore a buccaneering character called Argo Brassbottom; later in life, success induced a snobbish gentility that caused him to change his surname to Foxe. He was a dealer in surplus weapons, and had the notion that there must be money to be made from the disposal of the vast accumulation of large, out-of-date ICBMs and other military rocket vehicles. The nuclear warheads could be, and would be, reprocessed as plutonium plowshares or future swords under strict governmental control. But what of the rocket carcasses full of solid propellant? These could not safely be disassembled and reused but they could, without modification, be the key components of a private space program. Brassbottom, through his many contacts in the civil and military services of the West and East, soon found that there would indeed be a reward for disposing of these unwanted rockets. Then he had another bright idea. His main line of business was as an industrial scavenger, a human dung beetle who profited from the disposal of toxic wastes and other noxious products that we prefer not to notice. Why not, he thought, use the rockets to propel the toxic wastes right outside the Earth? Deep space could be a safe dumping place.

***

My thoughts about religion when a child grew from those of my father and the country folk I knew. It was an odd mixture, composed of witches, May trees, and the views expressed by Quakers, in and outside the Sunday school at a Friends' meeting house. Christmas was more of a solstice feast than a Christian one. We were, as a family, well into the present century, yet still amazingly superstitious. So ingrained was my childhood conditioning about the power of the occult that in later life it took a positive act of will to stop touching wood or crossing fingers whenever some hazard was to be faced. Christianity was there not so much as a faith, rather as a set of sensible directions on how to be good.

***

Thinking of the Earth as alive makes it seem, on happy days, in the right places, as if the whole planet were celebrating a sacred ceremony.

***

That is only what I feel about Gaia. What about God? I am too committed to the scientific way of thinking to feel comfortable when enunciating the Creed or the Lord's Prayer in a Christian Church. The insistence of the definition "I believe in God the Father Almighty, Maker of Heaven and Earth" seems to anesthetize the sense of wonder, as if one were committed to a single line of thought by a cosmic legal contract. It seems wrong also to take it merely as a metaphor. But I respect the intuition of those who do believe, and I am moved by the ceremony, the music, and most of all by the glory of the words of the prayer book that to me are the nearest to perfect expression of our language.

***

At a meeting in London recently, a wise man, Dr. Donald Braben, asked me: "Why do you stop with the Earth? Why not consider if the Solar System, the Galaxy, or even the Universe is alive?" My instant answer was that the concept of a living Earth, Gaia, is manageable.

***

Those millions of Christians who make a special place in their hearts for the Virgin Mary possibly respond as I do. The concept of Jahweh as remote, all-powerful, all-seeing is either frightening or unapproachable. Even the sense of presence of a more contemporary God, a still, small voice within, may not be enough for those who need to communicate with someone outside. Mary is close and can be talked to. She is believable and manageable. It could be that the importance of the Virgin Mary in faith is something of this kind, but there may be more to it. What if Mary is another name for Gaia? Then her capacity for virgin birth is no miracle or parthenogenetic aberration, it is a role of Gaia since life began. Immortals do not need to reproduce an image of themselves; it is enough to renew continuously the life that constitutes them. Any living organism a quarter as old as the Universe itself and still full of vigor is as near immortal as we ever need to know. She is of this Universe and, conceivably, a part of God. On Earth she is the source of life everlasting and is alive now; she gave birth to humankind and we are a part of her. This is why, for me, Gaia is a religious as well as a scientific concept, and in both spheres it is manageable.

***

Our humanist concerns about the poor of the inner cities or the Third World, and our near-obscene obsession with death, suffering, and pain as if these were evil in themselves -- these thoughts divert the mind from our gross and excessive domination of the natural world.

***

Individuals interact with Gaia in the cycling of the elements and in the control of the climate, just like a cell does in the body.

***

A frequent misunderstanding of my vision of Gaia is that I champion complacence, that I claim feedback will always protect the environment from any serious harm that humans might do. It is sometimes more crudely put as "Lovelock's Gaia gives industry the green light to pollute at will." The truth is almost diametrically opposite. Gaia, as I see her, is no doting mother tolerant of misdemeanors, nor is she some fragile and delicate damsel in danger from brutal mankind. She is stern and tough, always keeping the world warm and comfortable for those who obey the rules, but ruthless in her destruction of those who transgress. Her unconscious goal is a planet fit for life. If humans stand in the way of this, we shall be eliminated with as little pity as would be shown by the micro-brain of an intercontinental ballistic nuclear missile in full flight to its target.

***

I have tried to show that God and Gaia, theology and science, even physics and biology are not separate but a single way of thought.

***

In no way do I see Gaia as a sentient being, a surrogate God. To me Gaia is alive and part of the ineffable Universe and I am a part of her.

***

Science has its fashions, and one thing guaranteed to stir interest and start a new fashion is the exploration of a pathology. Health is far less interesting than disease....Theoretical ecology, as we have already discussed, is more concerned with sick than with healthy ecosystems. The vagaries of weather are more interesting than the long-term stability of climate. Continuous creation never had a chance in face of the ultimate pathology of the Big Bang.

***

When that great and good man Pope John Paul travels around the world, he, in an act of great humility and respect for the Mother or Father Land, bends down and kisses the airport tarmac. I sometimes imagine him walking those few steps beyond the dead concrete to kiss the living grass; part of our true Mother and of ourselves.

***

As a novice scientist I was interested in things like wild plants, especially the poisonous ones like henbane, aconite, and deadly nightshade.

***

The environmentalists, who should have seen what was happening and protested before it was too late, were much too busy fighting urban battles, or demonstrating outside the nuclear power stations. Their battle, whatever was claimed otherwise, was more against authority, represented by the monolithic electricity supply board, than for saving the countryside. They sometimes noticed poisonous sprays, for they were the products of the hated multinational chemical industries. But few were the friends of the soil who protested the agribusiness farms, or noticed the mechanized army of diggers and cutters working to make the landscape sterile for next year's planting of grain. There is no excuse for their neglect.

***

My vision of a future England would be like Blake's: to build Jerusalem on this green and pleasant land.

***

Left to herself, Gaia will relax again into another long ice age. We forget that the temperate Northern Hemisphere, the home of the rich First World, now enjoys a brief summer between long, long periods of winter that last for a hundred thousand years. Even the nukes would not so devastate the land; nor would a "nuclear winter," if it could happen at all, last long enough to return the land to its normal frozen state.

***

As a metaphor, Gaia emphasizes most the significance of the individual organism. It is always from the action of individuals that powerful local, regional, and global systems evolve. When the activity of an organism favors the environment as well as the organism itself, then its spread will be assisted; eventually the organism and the environmental change associated with it will become global in extent. The reverse is also true, and any species that adversely affects the environment is doomed; but life goes on.

***

Gaia theory arose from a detached, extraterrestrial view of the Earth, too distant to be much concerned with humans. Strangely, the view is not inconsistent with the human values of kindness and compassion; indeed it helps us to reject sentimentality about pain and death, and accept mortality, for us as well as for our species. With such a view in mind, Helen and I wish our eight grandchildren to inherit a healthy planet. In some ways, the worst fate that we can imagine for them is to become immortal through medical science -- to be condemned to live on a geriatric planet, with the unending and overwhelming task of forever keeping it and themselves alive for our kind of life. Death and decay are certain, but they seem a small price to pay for the possession, even briefly, of life as an individual. The second law of thermodynamics points the only way the Universe can run-down, to a heat death.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:18 pm

Inside Cover:

Viewed from the distance of the moon, the astonishing thing about the Earth, catching the breath, is that it is alive. -- Lewis Thomas

THE AGES OF GAIA

To the ancient Greeks the Earth was a living goddess, Gaia. This profound book replaces myth with science. Drawing on the latest developments in geology, geochemistry, evolutionary biology, and climatology, and his own path-breaking research, James Lovelock offers a new scientific synthesis in harmony with the Greek conception of the Earth as a living whole, as Gaia.

Conventional science has depicted the Earth as little more than inert rock, upon which plants and animals happen to live. Lovelock's Gaia theory shows us a vastly different world, one great circuit of life from its fiery core to its outer atmosphere. "Just as the shell is part of the snail, so the rocks, the air, and the oceans are part of Gaia," Lovelock writes.

In 1979 James Lovelock first sketched out this theory in his best seller, Gaia: A New Look at Life on Earth. Many scientists dismissed its implications outright; others labored mightily to refute them. Meanwhile, ordinary people all over the world embraced the Gaia theory. In less than ten years, amid great controversy, the Gaia theory has moved from the margins of scientific research to become the subject of international conferences of scientists working in many different fields. The Ages of Gaia: A Biography of Our Living Earth gives us the hard-won results of these years, and fills out the sketch of Gaia into a full picture of its history and current health.

Like Rachel Carson's Silent Spring, this is a book whose message has the power to change the way we see the Earth itself, and our future on it. For James Lovelock not only tells us how the species and the material environment of Gaia have evolved in a single, indivisible, self-regulating process. He tells us, too, of the stresses -- all man-made -- which Gaia now endures. Species extinction, pollution -- especially the burning of fossil fuels and the resulting greenhouse effect, and deforestation -- all threaten Gaia's health and, ultimately, the life that we share in it.

But Gaia is remarkably resilient, forever changing as life and the Earth evolve together. In this book James Lovelock holds Gaia still "long enough for us to begin to understand her and to see how fair she is." He invites us all to join in the birth of a new science, geophysiology, dedicated to preserving the Earth.

Born in 1919, James Lovelock was educated at the University of London and Manchester University and holds a Ph.D. in medicine. In the United States, he has taught at Yale, the Baylor University College of Medicine, and, as a Rockefeller Fellow, at Harvard. An independent scientist, Lovelock works out of a barn-turned-laboratory at Coombe Mill in Cornwall, England. He is president of the Marine Biology Association, a fellow of the Royal Society, London, and author of Gaia: A New Look at Life on Earth.

Back Cover:

Image
Credit: J.S. Gifford

This book by James Lovelock describes a set of observations about the life of our planet which may, one day, be recognized as one of the major discontinuities in human thought. If Lovelock turns out to be as right in his view of things as I believe he is, we will be viewing the Earth as a coherent system of life, self-regulating and self-changing, a sort of immense living organism." -- Lewis Thomas, from the Foreword to The Ages of Gaia.

***

Viewed from the distance of the moon, the astonishing thing about the earth, catching the breath, is that it is alive. The photographs show the dry, pounded surface of the moon in the foreground, dead as an old bone. Aloft, floating free beneath the moist, gleaming membrane of bright blue sky, is the rising earth, the only exuberant thing in this part of the cosmos. If you could look long enough, you would see the swirling of the great drifts of white cloud, covering and uncovering the half-hidden masses of land. If you had been looking a very long, geologic time, you could have seen the continents themselves in motion, drifting apart on their crustal plates, held aloft by the fire beneath. It has the organized, self-contained look of a live creature, full of information, marvelously skilled in handling the sun. -- Lewis Thomas, The Lives of a Cell
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:19 pm

Foreword

Most working scientists have an awareness and respect for the history of the fields in which they labor, but what they generally have in mind is a series of endeavors strung through the volumes of their specialized journals that are still held in the library stacks -- not at all the much longer stretch of time and work that professional scholars would require for a proper history of science.

It is not that researchers have short memories, but that they learn and retain only the events that set their fields atremble in the first place. And for most of science these days, perhaps all of it, the great changes that launched this century's vast transformation of human knowledge began within this century, or at least seemed to. The modern postdoctoral student in a laboratory engaged in molecular biology, for instance, feels no dependence on generations of forebears more than 20 years back. The contemporary physicists may track their ideas back almost a century, to the beginnings of quantum theory, but it is the concepts emerging in only the past decade that are regarded as the real history. The cosmologists are out on totally new ground, looking in amazement at strange, unanticipated kinds of space and time, making educated guesses at phenomena far beyond the suburban solar system or the local galaxy, even speculating about universes bubbling out at the boundaries of this one.

We are, quite literally, in a new world, a much more peculiar place than it seemed a few centuries back, harder to make sense of, riskier to speculate about, and alive with information which is becoming more accessible and bewildering at the same time. It sometimes seems that there is not just more to be learned, there is everything to be learned.

This is far from the general public view of the matter, as reflected in the science sections of newspapers and newsmagazines. The nonscientific layman tends to take technology to be so closely linked to science as to be the center of the enterprise. The progress of science and that of technology seem to be all of a piece -- machines, electronics, computer chips, Mars landings, nonbiodegradable plastics, the ozone hole, the bomb, all the rest of what now looks like twentieth-century culture.

What is not so clearly seen is the newness of the scientific information itself, the strangeness, and, where meaning is to be discerned, the meaning. There is a great difference between the intellectual product of modern science and the various technologies that are sometimes (nothing like as frequently as the public might guess) derived from that product.

The books in this series, sponsored by The Commonwealth Fund, represent an attempt to clarify this distinction, as well as to provide a closer look at what goes on in the minds of scientists as they go about their work.

The Commonwealth Fund...was founded in 1918 with an endowment of almost $10 million by Anna M. Harkness...widow of Stephen V. Harkness, a principal investor in Standard Oil...Anna’s son, Edward Stephen Harkness, became the Commonwealth Fund’s first president and hired a staff of people to help him build the foundation.... Through additional gifts and bequests between 1918 and 1959, the Harkness family's total contribution to the Fund's endowment amounted to more than $53 million. Today, the Commonwealth Fund’s endowment stands at almost $700 million....While The Commonwealth Fund does not typically accept donations, several gifts to the foundation have increased the endowment and expanded the scope of the Commonwealth Fund’s projects and programs....

The Commonwealth Fund’s Program on Federal and State Health Policy is designed to strengthen the link between the work of the foundation, including the Commission on a High Performance Health System, and policy processes at the federal and state levels. The program hosts an annual Bipartisan Congressional Health Policy Conference for members of Congress, as well as other briefings for congressional members and their staff throughout the year.

-- Commonwealth Fund, by Wikipedia


This book by James Lovelock describes a set of observations about the life of our planet which may, one day, be recognized as one of the major discontinuities in human thought. If Lovelock turns out to be as right in his view of things as I believe he is, we will be viewing the Earth as a coherent system of life, self-regulating, self-changing, a sort of immense organism. This is not likely, in my opinion, to lead directly or indirectly to any specific piece of new technology to be put to use, although it may very well begin to influence, in new and gentler ways, the other sorts of technology we might be selecting for use in the future.

The selection of this book, and of others in The Commonwealth Fund Book Program, has been the responsibility of an Advisory Committee consisting of: Alexander G. Beam, M.D.; Donald S. Fredrickson, M.D.; Lynn Margulis, Ph.D.; Maclyn McCarty, M.D.; Lady Jean Medawar; Berton Roueche; Frederick Seitz, Ph.D.; and Otto Westphal, M.D. The publisher is represented by Edwin Barber, senior vice president, W. W. Norton & Company. Antonina W. Bouis serves as managing editor of the series, and Stephanie Hemmert as secretary. Margaret Mahoney, president of The Commonwealth Fund, has actively supported the work of the Advisory Committee at every turn.

Lewis Thomas, M.D., Editor, The Commonwealth Fund Book Program
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:20 pm

Preface

I am writing in a room added to what was once a water mill that drew power from the River Carey as it flowed on to join the Tamar and the sea. Coombe Mill is still a work place, but now a laboratory, den, and meeting place where I spend much of my time. The room looks out onto the river valley with its small fields and hedgerows typical of the Devonshire country scene.

The description of the place where this book was written is relevant to its understanding. I work here and it is my home. There is no other way to work on an unconventional topic such as Gaia. The researches and expeditions to discover Gaia have occupied nearly twenty years, and have been paid for from the income I receive for the invention and development of scientific instruments. I gratefully acknowledge the generosity of Helen Lovelock for letting me use the greater part of our joint income this way and also the faithful and consistent role of the Hewlett Packard Company, who have been the best of customers for my inventions, and truly have made the research possible.

Science, unlike other intellectual activities, is almost never done at home. Modern science has become as professional as the advertising industry. And, like that industry, it relies on an expensive and exquisitely refined technique. There is no place for the amateur in modern science, yet, as is often the way with professions, science more often applies its expertise to the trivial than to the numinous. Where science differs from the media is in its lack of a partnership with independent individuals. Painters, poets, and composers easily move from their own worlds into advertising and back again, and both worlds are enriched. But where are the independent scientists?

Definition of NUMINOUS: 1: supernatural, mysterious; 2: filled with a sense of the presence of divinity: holy; 3: appealing to the higher emotions or to the aesthetic sense: spiritual

-- Merriam-Webster Dictionary


You may think of the academic scientist as the analogue of the independent artist. In fact, nearly all scientists are employed by some large organization, such as a governmental department, a university, or a multinational company. Only rarely are they free to express their science as a personal view. They may think that they are free, but in reality they are, nearly all of them, employees; they have traded freedom of thought for good working conditions, a steady income, tenure, and a pension. They are also constrained by an army of bureaucratic forces, from the funding agencies to the health and safety organizations. Scientists are also constrained by the tribal rules of the discipline to which they belong. A physicist would find it hard to do chemistry and a biologist would find physics well-nigh impossible to do. To cap it all, in recent years the "purity" of science is ever more closely guarded by a self-imposed inquisition called the peer review. This well, meaning but narrow-minded nanny of an institution ensures that scientists work according to conventional wisdom and not as curiosity or inspiration moves them. Lacking freedom they are in danger of succumbing to a finicky gentility or of becoming, like medieval theologians, the creatures of dogma.

As a university scientist I would have found it nearly impossible to do full-time research on the Earth as a living planet. To start with, there would be no funds approved for so speculative a research. If I had persisted and worked in my lunch hour or spare time, it would not have been long before I received a summons from the lab director. In his office I would have been warned of the dangers to my career of persisting in so unfashionable a research topic. If this did not work and obstinately I persisted, I would have been summoned a second time and warned that my work endangered the reputation of the department, and the director's own career.

I wrote the first Gaia book so that a dictionary was the only aid needed and I have tried to write this way in the present book. I am puzzled by the response of some of my scientific colleagues who take me to task for presenting science this way. Things have taken a strange turn in recent years; almost the full circle from Galileo's famous struggle with the theological establishment. It is the scientific establishment that makes itself esoteric and is the scourge of heresy.

It was not always like this. You may well ask, Whatever became of those colorful romantic figures, the mad professors, the Drs. Who? Scientists who seemed to be free to range over all of the disciplines of science without let or hindrance? They still exist, and in some ways I am writing as a member of their rare and endangered species.

More seriously, I have had to become a radical scientist also because the scientific community is reluctant to accept new theories as fact, and rightly so. It was nearly 150 years before the notion that heat is a measure of the speed of molecules became a fact of science, and 40 years before plate tectonics was accepted by the scientific community.

Now perhaps you see why I work at home supporting myself and my family by whatever means come to hand. It is no penance, rather a delightful way of life that painters and novelists have always known about. Fellow scientists join me, you have nothing to lose but your grants.

The main part of this book, chapters 2 to 6, is about a new theory of evolution, one that does not deny Darwin's great vision but adds to it by observing that the evolution of the species of organisms is not independent of the evolution of their material environment. Indeed the species and their environment are tightly coupled and evolve as a single system. What I shall be describing is the evolution of the largest living organism, Gaia.

My first thoughts about Gaia came when I was working in Norman Horowitz's biosciences division of the Jet Propulsion Laboratory, where we were concerned with the detection of life on other planets. These preliminary ideas were expressed briefly in the proceedings of a meeting held by the American Astronautical Society in 1968 and more definitely in a letter to Atmospheric Environment in 1971. But it was not until two years later, following an intense and rewarding collaboration with the biologist Lynn Margulis, that the skeleton Gaia hypothesis grew flesh and came alive. The first papers were published in the journals Tellus and Icarus, where the editors were sympathetic and were prepared to see our ideas discussed.

Lynn Margulis is the staunchest and best of my colleagues. I am also fortunate in that she is unique among biologists in her broad understanding of the living world and its environment. At a time when biology has divided itself into some thirty or more narrow specialties proud in their ignorance of other sciences, even of other biological disciplines, it needed someone with Lynn's rare breadth of vision to establish a biological context for Gaia.

Sometimes, when confronted with excesses of sentiment about life on Earth, I follow Lynn's lead and take on the role of shop steward, the trade union representative, of microorganisms and the lesser under-represented forms of life. They have worked to keep this planet fit for life for 3.5 billion years. The cuddly animals, the wildflowers, and the people are to be revered, but they would be as nothing were it not for the vast infrastructure of the microbes.

It would be difficult after spending nearly twenty years developing a theory of the Earth as a living organism -- where the evolution of the species and their material environment are tightly coupled but still evolve by natural selection -- to avoid capturing views about the problems of pollution and the degradation of the natural environment by humans.

Gaia theory forces a planetary perspective. It is the health of the planet that matters, not that of some individual species of organisms. This is where Gaia and the environmental movements, which are concerned first with the health of people, part company. The health of the Earth is most threatened by major changes in natural ecosystems. Agriculture, forestry, and to a lesser extent fishing are seen as the most serious sources of this kind of damage with the inexorable increase of the greenhouse gases, carbon dioxide, methane, and several others coming next. Geophysiologists do not ignore the depletion of the ozone layer in the stratosphere with its concomitant risk of increased irradiation with short-wave ultraviolet, or the problem of acid rain. These are seen as real and potentially serious hazards but mainly to the people and ecosystems of the First World -- from a Gaian perspective, a region that is clearly expendable. It was buried beneath glaciers, or was icy tundra, only 10,000 years ago. As for what seems to be the greatest concern, nuclear radiation, fearful though it is to individual humans is to Gaia a minor affair. It may seem to many readers that I am mocking those environmental scientists whose life work is concerned with these threats to human life. This is not my intention. I wish only to speak out for Gaia because there are so few who do, compared with the multitudes who speak for the people.

Because of this difference in emphasis, a concern for the planet rather than for ourselves, I came to realise that there might be the need for a new profession, that of planetary medicine. I am indebted to the historian Donald McIntyre for writing to tell me that it was James Hutton who first introduced the idea of planetary physiology in the eighteenth century. Hutton was a physician as well as a geologist. Physiology was the first science of medicine, and one of the aims of this book is to establish "geophysiology" as a basis for planetary medicine. At this early stage in our understanding of the Earth as a physiological entity, we need general practitioners, not specialists. We are like physicians before the use of antibiotics; even in the 1930s they could offer little other than symptomatic relief to patients suffering from infection. Now the major causes of death in the early part of this century -- tuberculosis, diphtheria, whooping cough, pneumonia -- have vastly declined, and physicians are mostly concerned with the diseases of degeneration -- cardiovascular and neoplastic disease. It is true that the appearance of the HIV virus has shaken the confidence we had in medicine to cure all ills, but still we have advanced far beyond the helplessness of the days before the 1940s.

We are in the same condition now with respect to the health of the Earth as were the early physicians. Specialties, like biogeochemistry, theoretical ecology, and evolutionary biology, all exist, but they have no more to offer the concerned environmental physician or the patient than could the analogous science of biochemistry and microbiology in the nineteenth century.

As part of their graduation, physicians must take the Hippocratic Oath. It includes the injunction to do nothing that would harm the patient. A similar oath is needed for putative planetary doctors if they are to avoid iatrogenic error: an oath to prevent the overzealous from applying a cure that would do more harm than good. Consider, for example, an industrial disaster that contaminated a whole geographic region with easily measurable levels of some carcinogenic agent, one that posed a calculable risk to the whole population of the region. Should all the food crops and livestock of the region be destroyed to prevent the risk attendant upon their consumption? Should nature, instead, just take its course? Or should we aim for some less stark choice in between? A recent disaster illustrates how, in the absence of the voice of the planetary physician, treatment may be applied with consequences more severe than those of the poison. I refer to the tragedy of Swedish Lapland in the wake of the Chernobyl accident, where thousands of reindeer, the food prey of the Lapps, were destroyed, because it was thought they were too radioactive to eat. Was it justifiable to inflict this brutal treatment for mild radioactive poisoning on a fragile culture and its dependent ecosystem? Or were the consequences of the "cure" worse than the remote and theoretical risk of cancer in a small proportion of its inhabitants?

In addition to a chapter on these environmental affairs, the last part of the book is concerned with some speculations about establishing a geophysiological system on Mars. The first Gaia book also stirred an interest in the religious aspects of Gaia, so in another chapter I have tried to answer some of the difficult questions that were raised. In this unfamiliar territory I have benefited from the strong moral support of the Lindisfarne Fellowship and especially from its founders, William Irwin Thompson and James Morton, and from the friendship of its other members, like Mary Catherine Bateson, John and Nancy Todd, and Stewart Brand, who was for many years the editor of CoEvolution Quarterly.

THE WICCA CULT: The WICCA cult came to the surface early during the post-war period, as a legalized association for the promotion of witchcraft. It is the leading publicly known international association of witches in the world today. In the United States, WICCA's outstanding sponsor is the New York Anglican (Episcopal) diocese, under Bishop Paul Moore. Officially, New York's Anglican Cathedral of St. John the Divine has promoted the spread of WICCA witchery through its Lindisfarne center. The late Gregory Bateson conducted such an operation out of the Lindisfarne center during the 1970s. No later than the 1970s, and perhaps still today, the crypt of the Cathedral of St. John the Divine, is the headquarters for solemn ceremonies of the British (Venerable) Order of Malta. Key figures, such as Gregory Bateson's former spouse, Dame Margaret Mead, associated with that British order, have been associated with projects in support of the Satanist "Age of Aquarius" cause.

-- Real History of Satanism, by Lyndon LaRouche


From the days when I first started writing and thinking about Gaia I have been constantly reminded how often the same general idea has been posed before, I have felt a special empathy with the writings of the ecologist Eugene Odum. If I unintentionally offend prior "geophysiologists" by failing to give credit to their writings, I ask their forgiveness. I know that there must be numerous other thinkers, like the Bulgarian philosopher, Stephen Zivadin, who have said much of it before me and have been ignored.

I have been fortunate in the friends who have read and criticized the chapters of the book as it was written. Peter Fellgett, Gail Fleischaker, Robert Garrels, Peter Liss, Andrew Lovelock, Lynn Margulis, Euan Nisbet, Andrew Watson, Peter Westbroek, and Michael Whitfield, all have unstintingly and thoughtfully given their advice on the science. I am equally thankful to my friends who criticised the book in terms of its readability: Alex and Joyce Andrew, Stewart Brand, Peter Bunyard, Christine Curthoys, Jane Gifford, Edward Goldsmith, Adam Hart-Davis, Mary McGowan, and Elizabeth Sachtouris. Since 1982 the United Nations University, through its program officer, Walter Shearer, has provided moral and material support especially for the notion of planetary medicine.

Left to myself I tend to write blocks of text that, like the pattern of a mosaic, make sense only from a distant view. I greatly valued the friendly skill with which Jackie Wilson rearranged my words as she edited the manuscript and made it readable.

The Commonwealth Fund Book Program, by their generous support, gave me the opportunity to set aside the time needed to develop the ideas of the book and to write. I am especially grateful to Lewis Thomas and to the two editors Helene Friedman and Antonina Bouis for the warmth of their encouragement and moral support.

But this book could never have been written without the sustenance and love that Helen and John Lovelock so freely gave.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:22 pm

THE AGES OF GAIA

Image
Emiliana huxleyii, known by her friends as Emily, is one of the more important members of the biota. Blooms of these phytoplankton cover large areas of ocean; their presence powerfully affects the environment through their capacity to facilitate the removal of carbon dioxide from the air and their production of dimethyl sulfide (which acts to nucleate clouds over the oceans).

1: Introductory

All through my boyhood I had a profound conviction that I was no good, that I was wasting my time, wrecking my talents, behaving with monstrous folly and wickedness and ingratitude -- and all this, it seemed, was inescapable, because I lived among laws which were absolute, like the law of gravity, but which it was not possible for me to keep.

-- George Orwell, A Collection of Essays


Of all the prizes that come from surviving more than fifty years the best is the freedom to be eccentric. What a joy to be able to explore the physical and mental bounds of existence in safety and comfort, without bothering whether I look or sound foolish. The young usually find the constraints of convention too heavy to escape, except as part of a cult. The middle-aged have no time to spare from the conservative business of living. Only the old can happily make fools of themselves.

The idea that the Earth is alive is at the outer bounds of scientific credibility. I started to think and then to write about it in my early fifties. I was just old enough to be radical without the taint of senile delinquency. My contemporary and fellow villager, the novelist William Golding, suggested that anything alive deserves a name -- what better for a living planet than Gaia, the name the Greeks used for the Earth Goddess?

Definition of LIFE: 1a: the quality that distinguishes a vital and functional being from a dead body b: a principle or force that is considered to underlie the distinctive quality of animate beings c: an organismic state characterized by capacity for metabolism, growth, reaction to stimuli, and reproduction

-- Merriam Webster Dictionary


The concept that the Earth is actively maintained and regulated by life on the surface had its origins in the search for life on Mars. It all started one morning in the spring of 1961 when the postman brought a letter that was for me almost as full of promise and excitement as a first love letter. It was an invitation from NASA to be an experimenter on its first lunar instrument mission. The letter was from Abe Silverstein, director of the NASA space flight operations. I can still recall the joyous and lasting incredulity.

Space is only a hundred miles away and is now a common place. But 1961 was only four years after the Soviet Union had launched the first artificial satellite, Sputnik. I listened to it bleeping its simple message that showed we could escape from Earth. Only six years earlier a distinguished astronomer said, when asked what he thought of the possibility of an artificial satellite, "Utter bunk." To receive an official invitation to join in the first exploration of the Moon was a legitimization and recognition of my private world of fantasy. My childhood reading had moved on that well-known path from Grimm's Fairy Tales through Alice's Adventures in Wonderland to Jules Verne and H. G. Wells. I had often said in jest that it was the task of scientists to reduce science fiction to practice. Someone had listened and called my bluff.

My first encounter with the space science of NASA was to visit that open-plan cathedral of science and engineering, the Jet Propulsion Laboratory, just outside the suburb of Pasadena in California. Soon after I began work with NASA on the lunar probe, I was moved to the even more exciting job of designing sensitive instruments that would analyze the surfaces and atmospheres of the planets. My background, though, was biology and medicine, and I grew curious about the experiments to detect life on other planets. I expected to find biologists engaged in designing experiments and instruments as wonderful and exquisitely constructed as the spacecraft themselves. The reality was a disappointment that marked the end of my euphoria. I felt that their experiments had little chance of finding life on Mars, even if the planet were swarming with it.

When a large organization is faced with a difficult problem the standard procedure is to hire some experts, and this is what NASA did. This approach is fine if you need to design a better rocket engine. But if the goal is to detect life on Mars, there are no such experts. There were no Professors of Life on Mars, so NASA had to settle for experts of life on Earth. These tended to be biologists familiar with the limited range of living things that they work with in their Earth-bound laboratories. There was no reason to suppose that such life forms would exist on Mars, even if life there were plentiful.

From the beginning to the end, the Martian life-detection experiments had a marked air of unreality. Let me illustrate this with a fable. Dr. X, an eminent biologist, showed me his Martian life detector; a cubical cage of stainless steel, beautifully constructed, with sides about one centimeter long. When I asked him how it worked, he replied, "It's a flea trap. Fleas are attracted to the bait inside, hop in, and cannot escape." I then asked how he could be sure that there are fleas on Mars; his response was, "Mars is the greatest desert in the Solar System -- a planet full of desert. Wherever there are deserts there are camels, and there is no animal with as many fleas as a camel. On Mars my detector will not fail to find life." I think that the other scientists at the Jet Propulsion Laboratory tolerated me as a devil's advocate. They were under great pressure to get on with the job, and so had little time to think about what the job really was. They viewed my questions about Martian fleas with amused skepticism.

I was sure that there was a better way. At that time Dian Hitchcock, a philosopher, visited the Jet Propulsion Laboratory, where she was employed by NASA to assess the logical consistency of the experiments. Together we decided that the most certain way to detect life on planets was to analyze their atmospheres. We published two papers suggesting that life on a planet would be obliged to use the atmosphere and oceans as conveyors of raw materials and depositories for the products of its metabolism. This would change the chemical composition of the atmosphere so as to render it recognizably different from the atmosphere of a lifeless planet. Even on Earth the Viking lander might have failed to find life had it landed on the antarctic ice. By contrast a full atmospheric analysis, which the Viking was not equipped to do, would have provided a clear answer; indeed, even in the 1960s, analyses of the Martian atmosphere were available from telescopes that used infrared instead of visible light to look at Mars. They revealed an atmosphere that was dominated by carbon dioxide and not far from the state of chemical equilibrium. The gases in the Earth's atmosphere, on the other hand, are in a persistent state of disequilibrium. This strongly suggested to us that Mars was lifeless.

This conclusion was not popular with our NASA sponsors. They badly needed reasons to support the cost of a Mars expedition, and what goal could be more enticing than the discovery of life there? A certain Senator Proxmire, staunch guardian of the public purse, might have been interested to learn that NASA was pressing on with a Martian landing, at great expense, even when scientists within the organization had said there could be no life there to find. He might have been outraged had he discovered that as part of our research, supported by NASA funds, Hitchcock and I had turned an imaginary telescope on our own planet to show that the Earth bore life in abundance.

During those exciting days we often argued about the life that might be on Mars and about the extent of its cover of the surface. In the late 1960s, NASA sent its Mariner spacecraft to view the surface from orbit around the planet. Their view showed Mars, like the Moon, to be extensively cratered, and tended to confirm the dismal prediction that Dian Hitchcock and I had made from a study of its atmospheric composition; that it was probably lifeless. I recall a gentle discussion with Carl Sagan, who thought it might still be possible that life existed in oases where local conditions would be more favorable. Long before Viking set course from Earth I felt intuitively that life could not exist on a planet sparsely; it could not hang on in a few oases, except at the beginning or at the end of its tenure. As Gaia theory developed, this intuition grew; now I view it as a fact.

There was much argument about the need to sterilize the spacecraft before sending them to Mars. I could never understand why it should be thought so bad to run the small risk of accidentally seeding Mars with life; it might even be the only chance we had of passing life on to another planet. Sometimes the argument was fierce and macho; full of adolescent masculinity. In any event, feeling as I did -- that Mars was dead -- the image of rape, sometimes used, could not be sustained; at worst the act would be only the dismal lonely aberration of necrophilia. More seriously, as an instrument designer I knew that the act of sterilization made all but impossible the already superhuman task of building the Vikings and threatened the integrity of their exquisitely engineered internal homeostasis.

To this day I appreciate the toleration and generosity of my colleagues at the Jet Propulsion Laboratory and in NASA, especially the personal kindness of Norman Horowitz, who was then head of the team of space biologists. In spite of the "bad news" I had brought, they continued to support my researches until the Viking missions to Mars were ready to go. The soft landing on Mars in 1975 of these two intricate and almost humanly intelligent robots was successful. Their mission was to find life on Mars, but the messages they returned as radio signals to the Earth returned only the chill news of its absence. Mars, except during day in the summer, was a place of pitiless frigidity, and implacably hostile to the warm wet life of Earth. The two Vikings now sit there brooding silently, no longer allowed to report the news from Mars, hunched against their final destruction by the wind with its burden of abrasive dust and corrosive acid. We have accepted the barrenness of the Solar System. The quest for life elsewhere is no longer an urgent scientific goal, but the confirmation by the Vikings of the utter sterility of Mars has hung as a dark contrasting backcloth for new models and images of the Earth. We now understand that our planet differs greatly from her two dead siblings, Mars and Venus.

That, then, is how the Gaia hypothesis started. We looked at the Earth in our imagination, and therefore with fresh eyes, and found many things, including the radiation from the Earth of an infrared signal characteristic of the anomalous chemical composition of its atmosphere. This unceasing song of life is audible to anyone with a receiver, even from outside the Solar System. I will try to show in the chapters that follow that unless life takes charge of its planet, and occupies it extensively, the conditions of its tenancy are not met. Planetary life must be able to regulate its climate and chemical state. Part-time or incomplete occupancy or mere occasional visits will not be enough to overcome the ineluctable forces that drive the chemical and physical evolution of a planet. The imaginary exercise of seeding Mars with life, or even of bringing Mars to life, is discussed in chapter 8. It is about the effort needed to bring Mars to a state fit for life and to maintain it in that state until life has taken charge. It illustrates the awesome extent to which the greater part of our own environment on Earth is always perfect and comfortable for life. The energy of sunlight is so well shared that regulation is, effectively, free of charge.

The Gaia hypothesis supposes the Earth to be alive, and considers what evidence there is for and against the supposition. I first put it before my fellow scientists in 1972 as a note with the title "Gaia as Seen Through the Atmosphere." It was brief, taking only one page of the journal Atmospheric Environment. The evidence was mostly drawn from the atmospheric composition of the Earth and its state of chemical disequilibrium. This evidence is reviewed in table 1.1 in comparison with modern knowledge of the compositions of the atmospheres of Mars and Venus, and with a guess at the atmosphere the Earth might have now, had it never known life. After long and intense discussions, Lynn Margulis and I produced more detailed yet concise statements in the journals Tellus and Icarus. Then in 1979, Oxford University Press published my book Gaia: A New Look at Life on Earth, which collected all our ideas up to that point. I began to write that book in 1976, when NASA's Viking spacecraft were about to land on Mars. I used their presence there as planetary explorers to set the scene for the discovery of Gaia, the largest living organism in the Solar System.

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Ten years on and it is time to write again; this time about getting to know Gaia and discovering what kind of life she is. The simplest way to explore Gaia is on foot. How else can you so easily be part of her ambience? How else can you reach out to her with all your senses? I was delighted a few years ago, therefore, to read of another man who enjoyed walking in the countryside and who also believed the Earth to be alive.

Yevgraf Maksimovich Korolenko lived over 100 years ago in Kharkov in the Ukraine. He was an independent scientist and philosopher. He too was in his sixties when he began to express and discuss ideas far too radical for the merely middle-aged. Korolenko was a learned man; although self-educated, he was familiar with the works of the great natural scientists of his time. He did not recognize any authority, philosophical, religious, or scientific, but tried to discover answers for himself. One of those with whom he shared his country walks and his radical ideas was his young cousin, Vladimir Vernadsky. Vernadsky, who was to become an outstanding Soviet scientist, was deeply impressed by the old man's assertion that "The Earth is an organism." But to Vernadsky's biographer, R. K. Balandin, this "is another of Korolenko's aphorisms. It is doubtful that young Vladimir Vernadsky should have remembered this aphorism half a century later. Nevertheless, Korolenko's naive analogy of the Earth as a living organism could not but excite the imagination of his young friend."

The idea that the Earth is alive is probably as old as humankind. But the first public expression of it as a fact of science was by a Scottish scientist, James Hutton. In 1785 he said, at a meeting of the Royal Society of Edinburgh, that the Earth was a superorganism and that its proper study should be physiology. He went on to compare the cycling of the nutritious elements in the soil, and the movement of water from the oceans to the land, with the circulation of the blood. James Hutton is rightly remembered as the father of geology, but his idea of a living Earth was forgotten, or denied, in the intense reductionism of the nineteenth century -- except in the minds of isolated philosophers like Korolenko.

Today, we all use the word "biosphere" rarely recognizing that it was Eduard Suess who in 1875 first used the term, in passing, when describing his work on the geological structure of the Alps. Vernadsky developed the concept, and from 1911 used its modern meaning. Vernadsky said: "The biosphere is the envelope of life, i.e. the area of living matter ... the biosphere can be regarded as the area of the Earth's crust occupied by transformers which convert cosmic radiations into effective terrestrial energy: electrical, chemical, mechanical, thermal, etc."

When I first formulated the Gaia hypothesis, I was entirely ignorant of the related ideas of these earlier scientists, especially Hutton, Korolenko, and Vernadsky. I was also unaware of similar ideas expressed in recent years by many scientists, such as Alfred Lotka, the founder of population biology, Arthur Redfield, an ocean chemist, and J. Z. Young, a biologist. I acknowledged only the inspiration of G. E. Hutchinson, a distinguished limnologist at Yale University, and of Lars Sillen, a Swedish geochemist. But I was not alone in this ignorance; in the vigorous objections to or support for Gaia made by colleagues in all sciences, none observed that what was said followed naturally from Vernadsky's view of the world. Even as late as 1983, the monumental Earth's Earliest Biosphere, edited by geologist J. W. Schopf and including contributions from twenty of the most distinguished American and European Earth scientists, made no mention of either Hutton or Vernadsky.

The all-too-common deafness of English speakers to any other language kept from our common knowledge the everyday science of the Russian-speaking world. It would be easy to attribute the lack of recognition of Vernadsky's contributions to the present political divisions, but, although this may play some part, I think that it is a small one compared with the malign effects of the nineteenth-century separation of science into neat compartments where specialists and experts could ply their professions in complacency. How many physicists are proud of their ignorance of what they call the "soft sciences"? How many biochemists can name the wildflowers of their countryside? In such a climate of opinion it is not surprising that Vernadsky' s biographer found Korolenko's statement, "The Earth is a living organism," to be naive. Most scientists today would agree with Balandin; yet few of them would be able to offer a satisfactory definition of life as an entity or a process.

In science, a hypothesis is really no more than a "let's suppose." The first Gaia book was hypothetical, and lightly written -- a rough pencil sketch that tried to catch a view of the Earth seen from a different perspective. Thoughtful criticisms of this first book led to new and deeper insights into Gaia. In a physiological sense the Earth was alive. Much new evidence has accumulated, and I have made new theoretical models. We can now fill in some of the finer details, though fortunately there seems little need to erase the original lines. As a consequence this second book is a statement of Gaia theory; the basis of a new and unified view of the Earth and life sciences. Because Gaia was seen from outside as a physiological system, I have called the science of Gaia geophysiology.

Why run the Earth and life sciences together? I would ask, why have they been torn apart by the ruthless dissection of science into separate and blinkered disciplines? Geologists have tried to persuade us that the Earth is just a ball of rock, moistened by the oceans; that nothing but a tenuous film of air excludes the hard vacuum of space; and that life is merely an accident, a quiet passenger that happens to have hitched a ride on this rock ball in its journey through space and time. Biologists have been no better. They have asserted that living organisms are so adaptable that they have been fit for any material changes that have occurred during the Earth's history. But suppose that the Earth is alive. Then the evolution of the organisms and the evolution of the rocks need no longer be regarded as separate sciences to be studied in separate buildings of the university. Instead, a single evolutionary science describes the history of the whole planet. The evolution of the species and the evolution of their environment are tightly coupled together as a single and inseparable process.

Science is not obsessively concerned with whether facts are right or wrong. The practice of science is that of testing guesses; forever iterating around and towards the unattainable absolute of truth. To scientists, Gaia is a new guess that is up for trial or a novel "bioscope" through which to look at life on Earth. In some sciences, Gaian ideas are appropriate, even if not welcomed, because the vision of the world through older theories is no longer sharp and clear. This is particularly true of theoretical ecology, evolutionary biology, and the Earth sciences generally.

Theoretical ecologists for forty years -- since Alfred Lotka and Vito Volterra made their simple models of a world populated only by rabbits and foxes -- have tried to understand the complex interactions between a real forest and its vast range of species. Their mathematical models, though good at simulating pathologies, fail to explain the long-term stability of the complex ecosystems of the humid tropical forests. Their models seem counterintuitive; they suggest that the fragility of ecosystems increases with their diversity. They imply that the farmer who rotates his crops and keeps his hedgerows and woodland intact is not only less efficient but less ecologically stable than the monoculture factory farm.

In recent times, the evolutionary biologists have engaged in a fiery argument. The normally placid pages of those cool scientific journals, Nature and Science, have burnt like an inner city, the conservative defenders of ordered gradual change reacting against a revolution for the right to interpret Darwin's great insight. Was evolution gradual or did it proceed, as Stephen Jay Gould and Niles Eldredge propose, with long periods of stasis punctuated by catastrophic change?

Geologists interested in the evolution of the rocks, ocean, and atmosphere are beginning to ponder about the persistence of the oceans on Earth when Mars and Venus are so dry. Then there is the puzzling constancy of the climate, in spite of an ever-increasing output of heat from the Sun.

These and other things that seem obscure within their separated fields of science become clear when seen as phenomena of a living planet. Gaia theory predicts that the climate and chemical composition of the Earth are kept in homeostasis for long periods until some internal contradiction or external force causes a jump to a new stable state. On such a living planet, we shall see that punctuated evolution and abundant oceans are normal and expected.

As a theory of a living Earth, this book is neither holistic nor reductionist. There are no sections on climatology, geochemistry, and so on. The next two chapters are a statement of Gaia theory. Then follow three chapters which give a geophysiologist's view of the history of the Earth from the start of life to the present day. These run chronologically, instead of chaotically by scientific discipline. The sequence starts with the beginning of life, the Archean, when the only organisms on Earth were bacteria, and when the atmosphere was dominated by methane and oxygen was only a trace gas. Next that middle age, which the geologists call the Proterozoic, from the first appearance of oxygen as a dominant atmospheric gas until the time when communities of cells gathered to form new collectives, each with its own identity. Then a chapter on the Phanerozoic, the time of the plants and animals. In each, the record of the rocks is interpreted through Gaia theory and the new interpretation compared with the conventional wisdom of the Earth and life sciences. The final chapters concern the present and future of Gaia, with an emphasis on the human presence both on Earth and as it may one day exist on Mars. What would it take to bring Mars to life?

The arbitrariness of even a chronological division is underlined by the persistence of the Archean biota; their world has never ended, but lives on in our guts. Those bacteria have been with Gaia for nearly four thousand million years, and they still live all over the Earth in muds, sediments, and intestines -- wherever they can keep away from that deadly poison, oxygen.

Any new theory about the Earth cannot be kept a secret of science. It is bound to attract the attention of humanists, environmentalists, and those of religious beliefs and faiths. Gaia theory is as out of tune with the broader humanist world as it is with established science. In Gaia we are just another species, neither the owners nor the stewards of this planet. Our future depends much more upon a right relationship with Gaia than with the never-ending drama of human interest.

When our family lived in the village of Bowerchalke in Wiltshire, Helen and I would spend spring mornings seeking rare species of wild orchids. In those days, before its destruction by the machines of agribusiness vandals, the English countryside was a heavenly garden. Orchids grew in profusion on the downs, but the rarer kinds could be exceedingly hard to find. Much prior programming of the mind was needed to spot a musk orchid in the grass. It was an esoteric pastime. Much of science is done like this, and it can be enjoyable to discover new compounds or mathematical concepts or old ones in strange places. But these discoveries usually require rigorous mental and physical preparation and often the learning of a new language.

Gaia theory goes back to fundamentals, to genesis. Even geophysiology is too young a science to have a language. Therefore this second book is written like the first, so that anyone interested in the idea that the Earth is alive can read it. Neither a scientific text nor the workshop manual for a planetary engineer, it is one man's view of the world where we belong. Most of all the book is for entertainment, yours and mine. It was written as part of a way of life that included time to go for walks in the country and to talk with friends, as Korolenko did, about the Earth being alive.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:25 pm

Part 1 of 2

2: What Is Gaia?

You must not ... be too precise or scientific about birds and trees and flowers ...

-- Walt Whitman, Specimen Days


Travel back in your memory to the time when you first awoke, that exquisite moment of childhood when first you came alive -- the sudden rush of sound and sight, as if a television receiver had been switched on and was about to bring news of vast importance. I seem to recall sunlight and soft fresh air; then suddenly knowing who I was and how good it was to be alive.

To reminisce about the first memory of my personal life may seem irrelevant in our quest to understand Gaia. But it isn't. As a scientist I observe, measure, analyze, and describe phenomena. Before I can do these things I need to know what I am observing. In a broad sense it may be unnecessary to recognize a phenomena when observing it, but scientists almost always have preconceived notions of the object of their study. As a child I recognized life intuitively. As an adult wondering about the Earth's strange atmosphere -- a mixture made of incompatible gases such as oxygen and methane coexisting like foxes and rabbits in the same burrow -- I was forced to recognize Gaia, to intuit her existence, long before I could describe her in proper scientific terms.

The concept of Gaia is entirely linked with the concept of life. To understand what Gaia is, therefore, I first need to explore that difficult concept, life. They hate to admit it, but the life scientists, whether the natural historians of the nineteenth century or the biologists of the twentieth, cannot explain what life is in scientific terms. They all know what it is, as we have done since childhood; but in my view no one has yet succeeded in defining life. The idea of life, the sense of being alive, are the most familiar and the most difficult to understand of the concepts we meet. I have long thought that the answer to the question "What is life?" was deemed so important to our survival that it was classified "top secret" and kept locked up as an instinct in the automatic levels of the mind. During evolution, there was great selection pressure for immediate action: crucial to our survival is the instant distinction of predator from prey and kin from foe, and the recognition of a potential mate. We cannot afford the delay of conscious thought or debate in the committees of the mind. We must compute the imperatives of recognition at the fastest speed and, therefore, in the earliest-evolved and unconscious recesses of the mind. This is why we all know intuitively what life is. It is edible, lovable, or lethal.

Life as an object of scientific inquiry requiring precise definition is much more difficult. Even scientists, who are notorious for their indecent curiosity, shy away from defining life. All branches of formal biological science seem to avoid the question. In the Dictionary of Biology compiled by M. Abercrombie, C. J. Hickman, and M. L. Johnson, these three distinguished biologists succinctly define all manner of words like ontogeny (development), Pteridophyta (ferns), and ecdysis (a stage in insect development). Under the letter L there is leptotene (the first sign of chromosome pairing in meiosis) and limnology (the study of lakes), but nowhere is life mentioned. When the word life does appear in biology it is in rejection, as by the philosophically inclined N. W. Pirie who, in 1937, published an article entitled "The Meaninglessness of the Terms 'Life' and 'Living'."

The Webster and the Oxford dictionaries are not much more help. Both remind of the word's origin from the Anglo-Saxon lif. This may explain some of the reluctance of academic biologists to tangle with so elemental a concept as life. The tribal war between the Normans and the Saxons was long enduring; the medieval schoolmen, knowing where power and preference lay, chose to support the victorious Norman establishment and to keep Latin as their language. Life was another of those rude uncivilized Anglo-Saxon words, best avoided in polite company. The Latin equivalent of lif, anima, was even less help. It was close in meaning to that other four-letter Gothic word, soul.

To go back to the Webster dictionary, it defines life as:

That property of plants and animals (ending at death and distinguishing them from inorganic matter) which makes it possible for them to take in food, get energy from it, grow, etc.


The Oxford dictionary says much the same:

The property which differentiates a living animal or plant, or a living portion of organic tissue, from dead or nonliving matter; the assemblage of the functional activities by which this property is manifested.


If such manifestly inadequate definitions of life are all I have to work with, can I do much better defining the living organism of Gaia? I have found it very difficult, but if I am to tell you about it I must try. I can start with some simpler definitions and classifications. Living things such as trees and horses and even bacteria can easily be perceived and recognized because they are bounded by walls, membranes, skin, or waxy coverings. Using energy directly from the Sun and indirectly from food, living systems incessantly act to maintain their identity, their integrity. Even as they grow and change, grow and reproduce, we do not lose track of them as visible, recognizable entities. Although there are uncountable millions of individual organisms all growing and changing, their traits in common allow us to group them and recognize that they belong to species such as peacocks, dogs, or wheat. About ten million species are estimated to exist. When any individual fails to get energy and food, fails to act to maintain its identity, we realize it is moribund or dead.

An important step in our understanding is to recognize the significance of collections of living things. You and I are both composed of a collection of organs and tissues. The many beneficiaries of heart, liver, and kidney transplants testify eloquently that each of these organs can exist independently of the body when kept warm and supplied with nutrients. The organs themselves are made up of billions of living cells, each of which can also live independently. Then the cells themselves, as Lynn Margulis has shown, are communities of microorganisms that once lived free. The energy-transforming entities of animal cells (the mitochondria) and of plants (the mitochondria and the chloroplasts) both were once bacteria living independently.

Life is social. It exists in communities and collectives. There is a useful word in physics to describe the properties of collections: colligative. It is needed because there is no way to express or measure the temperature or the pressure of a single molecule. Temperature and pressure, say the physicists, are the colligative properties of a sensible collection of molecules. All collections of living things show properties unexpected from a knowledge of a single one of them. We, and some other animals, keep a constant temperature whatever the temperature of our surroundings. This fact could never have been deduced from the observations of a single cell from a human being. The tendency to constancy was first noted by the French physiologist Claude Bernard in the nineteenth century. His American successor in this century, Walter Cannon, called it homeostasis or the wisdom of the body. Homeostasis is a colligative property of life.

"This new interrelationship of Gaia with man is by no means fully established; we are not yet a truly collective species, corralled and tamed as an integral part of the biosphere, as we are as individual creatures. It may be that the destiny of mankind is to become tamed, so that the fierce, destructive, and greedy forces of tribalism and nationalism are fused into a compulsive urge to belong to the commonwealth of all creatures which constitutes Gaia."

-- James Lovelock, Gaia: A New Look at Life


We have no trouble with the idea that noble entities such as people are made up from an intricate interconnected set of cell communities. We don't find it too difficult to consider a nation or a tribe as an entity made up of its people and the territory they occupy. But what of large entities, like ecosystems and Gaia? It took the view of the Earth from space, either directly through the eyes of an astronaut, or vicariously through the visual media, to give us the personal sense of a real live planet on which the living things, the air, the oceans, and the rocks all combine in one as Gaia.

The name of the living planet, Gaia, is not a synonym for the biosphere. The biosphere is defined as that part of the Earth where living things normally exist. Still less is Gaia the same as the biota, which is simply the collection of all individual living organisms. The biota and the biosphere taken together form part but not all of Gaia. Just as the shell is part of a snail, so the rocks, the air, and the oceans are part of Gaia. Gaia, as we shall see, has continuity with the past back to the origins of life, and extends into the future as long as life persists. Gaia, as a total planetary being, has properties that are not necessarily discernible by just knowing individual species or populations of organisms living together.

The Gaia hypothesis, when we introduced it in the 1970s, supposed that the atmosphere, the oceans, the climate, and the crust of the Earth are regulated at a state comfortable for life because of the behavior of living organisms. Specifically, the Gaia hypothesis said that the temperature, oxidation state, acidity, and certain aspects of the rocks and waters are at any time kept constant, and that this homeostasis is maintained by active feedback processes operated automatically and unconsciously by the biota. Solar energy sustains comfortable conditions for life. The conditions are only constant in the short term and evolve in synchrony with the changing needs of the biota as it evolves. Life and its environment are so closely coupled that evolution concerns Gaia, not the organisms or the environment taken separately.

Most of my working life has been spent on the fringes of the life sciences, but I do not think of myself a biologist, nor do I believe would biologists accept me as one of them. When seen from outside, much of biology appears to be the building of data bases -- making the "whole life catalog." Sometimes, in a pensive mood, I fancy that to biologists the living world is a vast set of book collections held in interconnected libraries. In this dream, the biologists are like competent librarians who devise the most intricate classification of every new library they discover but never read the books. They sense that something is missing from their lives, and this feeling intensifies as new collections of books grow hard to find. I see the biologists expressing an almost palpable sense of relief when joined by molecular biologists who dare to start the even greater task of classifying the words the books contain. It means that the search for the answer to the awesome question of what the books are about can be put off until the new and infinitely detailed molecular classification is complete.

My imaginary world, populated by biologists as book collectors, is in no way intended as a slur on the life sciences. Left to my own devices in such a world I should have been much less constructive. Impatient of waiting for an answer to the question, "What is the meaning of the books?" I would have seized some of them for experimental tests -- for example, burning them in a calorimeter and measuring, accurately, the heat released. My sense of frustration would not have lessened when I discovered that the densely packed pages of an encyclopedia give no more heat than the same mass of plain paper. Like the biologists' classification, this physical experiment would have been profoundly unsatisfying because it would have put to Nature the wrong question.

Can we scientists, any of us, do better in our quest to understand life? There are three equally powerful approaches: molecular biology, the understanding of those information-processing chemicals that are the genetic basis of all life on Earth; physiology, the science concerned with living systems seen holistically; thermodynamics, the branch of physics that deals with time and energy and that connects living processes to the fundamental laws of the Universe. Of these sciences, the latter is the one that may go furthest in the quest to define life, yet so far has made the least progress. Thermodynamics grew from down-to-earth origins, the quest of engineers to make steam engines more efficient. It flourished in the last century, both taxing and entertaining the minds of the greatest scientists.

The first law of thermodynamics is about energy, or in other words, the capacity to do work. Energy, says the first law, is conserved. Energy in the form of sunlight falling on the leaves of a tree is used in many ways. Some is reflected so that we see the leaves as green, some is absorbed and warms them, and some is transformed to food and oxygen; ultimately, we eat the food, consume it with the oxygen we breathe, and so use the Sun's energy to move, to think, and to keep warm. The first law says that this energy is always conserved and that no matter how far it is dispersed the total always remains the same. The second law is about the dissymmetry of Nature. When heat is turned to work, some of it is wasted. The redistribution of the total quantity of energy in the Universe has direction, says the second law. It is always running down. Hot objects cool, but cool objects never spontaneously become hot. The law can appear to be broken when some metastable store of internal energy is tapped, as when a match is struck, or a piece of plutonium experiences nuclear fission, but once used up the energy cannot be recovered. The law was not broken, the energy was merely redistributed and the downward path maintained. Water does not flow up the rivers from the sea to the mountains. Natural processes always move towards an increase of disorder, and this disorder is measured by entropy. It is a quantity that always and inexorably increases.

Entropy is real, not some hazy notion invented by professors to make it easier to challenge students with difficult examination questions. Like the length of a piece of string or the temperature of wine in a glass, it is a measurable physical quantity. Indeed, like temperature, the entropy of a substance is, in a practical sense, zero at the absolute zero of -- 273°C. When heat is added to a material substance, not only the temperature increases but also the entropy. Unfortunately there is a complication: whereas temperature can be measured with a thermometer, entropy cannot be measured directly with an "entropometer." Entropy, measured in the units calories per gram per degree, is the total quantity of heat added, divided by the temperature.

Consider the lifeless perfection of a snowflake, a crystal so exquisitely ordered in its fractal pattern that it is one of the most intricate of nonliving things. The quantity of heat needed to melt a snowflake to a raindrop is 80 times larger than the quantity needed to warm the raindrop by a single degree of temperature. The increase of entropy when snowflakes melt is 80 times larger than when they warm from -1°C to the melting point. Alternatively, the formation of ice that expresses the ordered perfection of a snowflake represents a decrease of entropy of the same amount. Entropy is connected in quantitative terms with the orderliness of things. The greater the order, the lower the entropy.

I like to think of entropy as the quantity that expresses the most certain property of our present Universe: its tendency to run down, to burn out. Others see it as the direction of time's arrow, a progression inevitably from birth to death. Far from being something tragic or a cause of sorrow, this universal tendency to decay benefits us. Without the decay of the Universe there could have been no Sun, and without the superabundant consumption of its energy store the Sun could never have provided the light that let us be.

The second law is the most fundamental and unchallenged law of the Universe; not surprisingly, no attempt to understand life can ignore it. The first book I read on the question of life was by the Austrian physicist, Erwin Schrodinger. He was curious about biology and wondered if the behavior of the fundamental molecules of life could be explained by physics and biology. His famous little book, entitled What Is Life?, is a collection of the public lectures on this topic that he gave in Dublin during his exile there in the Second World War. He describes his objective on the first page:

The large important and very much discussed question is: How can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?


He goes on to write:

The obvious inability of present-day physics and chemistry to account for such events is no reason for doubting that they can be accounted for by those sciences.


In those times, physicists were accustomed to exploring the dead, near-equilibrium world of "periodic crystals" -- crystals whose regularity is predictable, one atom of one kind always following another of a different kind in a repeating pattern. Even these comparatively simple structures were complex enough to stretch to the limit the simple equipment then available. Organic chemists were discovering the intricate structures of the "aperiodic crystals" from living matter, such as the proteins, polysaccharides, and nucleic acids. They were still far from the present-day understanding of the chemical nature of genetic material. Schrodinger concluded that, metaphorically, the most amazing property and characteristic of life is its ability to move upstream against the flow of time. Life is the paradoxical contradiction to the second law, which states that everything is, always has been, and always will be running down to equilibrium and death. Yet life evolves to ever-greater complexity and is characterized by an omnipresence of improbability that would make winning a sweepstake every day for a year seem trivial by comparison. Even more remarkable, this unstable, this apparently illegal, state of life has persisted on the Earth for a sizable fraction of the age of the Universe itself. In no way does life violate the second law; it has evolved with the Earth as a tightly coupled system so as to favor survival. It is like a skilled accountant, never evading the payment of required tax but also never missing a loophole. Most of Schrodinger's book is an optimistic prediction of how life is knowable. The eminent molecular biologist, Max Perutz, has recently commented that little in Schrodinger's book is original, and what is original is often wrong. This may be true; but I, like many of my colleagues, still acknowledge a debt to Schrodinger for having set us thinking in a productive way.

The great physicist Ludwig Boltzmann expressed the meaning of the second law in an equation of great seemliness and simplicity: S = k(lnP), where S is that strange quantity entropy; k is a constant rightly called the Boltzmann constant; and lnP is the natural logarithm of the probability. It means what it says -- the less probable something is, the lower is its entropy. The most improbable thing of all, life, is therefore to be associated with the lowest entropy. Schrodinger was not happy to associate something as significant as life with a diminished quantity, entropy. He proposed, instead, the term "negentropy," the reciprocal of entropy -- that is, 1 divided by entropy or 1/S. Negentropy is large, of course, for improbable things like living organisms. To describe the burgeoning life of our planet as improbable may seem odd. But imagine that some cosmic chef takes all the ingredients of the present Earth as atoms, mixes them, and lets them stand. The probability that those atoms would combine into the molecules that make up our living Earth is zero. The mixture would always react chemically to form a dead planet like Mars or Venus.

Often in science the same idea is thought of in different contexts in different parts of the world. There is nothing occult about this. Ideas are in continuous use as currency in the exchanges between scientists and, like money, can be used to buy many different things. When Schrodinger was lecturing about negentropy in Dublin, Claude Shannon was investigating a similar quantity in the United States, but from a radically different perspective. Shannon, at the Bell Telephone Laboratories, was developing information theory. It started as a plain engineering quest to discover the physical factors that caused a message sent by cable or by radio to lose information as it passed from the sender to the receiver. Shannon soon discovered a quantity that always tended to increase; the size of the increase was a measure of the loss of information. In no experiment was the size of this quantity ever observed to decrease. On the advice of John Von Neumann, a mathematical physicist, Shannon named this quantity entropy because it so much resembled the entropy of the steam engineers. The reciprocal of Shannon's entropy is the quantity often called information. If we assume that the entropy Shannon discovered is the same as the entropy of the steam engineers, then the elusive quantity that Schrodinger associated with the improbability of life -- negentropy -- is comparable with Shannon's information. In mathematical terms, if S is the entropy then both negentropy and information are 1/S.

The reward that comes from persevering with thoughts about these difficult concepts is insight to illuminate our quest to understand life and Gaia. The contribution from Shannon's theory is that information is not just knowledge. Information, in thermodynamic terms, is a measure of the absence of ignorance. Better to know all about a simple system than merely a great deal about a complex one. The less the ignorance, the lower the entropy. This is why it is so difficult to grasp the concept of Gaia from the voluminous but isolated knowledge of a single scientific discipline.

If the second law tells us that entropy in the Universe is increasing, how does life avoid the universal tendency for decay? A physicist in Britain, J. D. Bernal, tried to balance the books. In 1951, he wrote in recondite terminology: "Life is one member of the class of phenomena which are open or continuous reaction systems able to decrease their internal entropy at the expense of free energy taken from the environment and subsequently rejected in degraded form." Many other scientists have expressed these words as a mathematical equation. Among the clearest and most readable are the statements in a small book, The Thermodynamics of the Steady State, written by a physical chemist, K. G. Denbigh. They can be restated less rigorously but more comprehensibly as follows. By the act of living, an organism continuously creates entropy and there will be an outward flux of entropy across its boundary. You, as you read these words, are creating entropy by consuming oxygen and the fats and sugars stored in your body. As you breathe, you excrete waste products high in entropy into the air, such as carbon dioxide, and your warm body emits to your surroundings infrared radiation high in entropy. If your excretion of entropy is as large or larger than your internal generation of entropy, you will continue to live and remain a miraculous, improbable, but still legal avoidance of the second law of the Universe. "Excretion of entropy" is just a fancy way of expressing the dirty words excrement and pollution. At the risk of having my membership card of the Friends of the Earth withdrawn, I say that only by pollution do we survive. We animals pollute the air with carbon dioxide, and the vegetation pollutes it with oxygen. The pollution of one is the meat of another. Gaia is more subtle, and, at least until humans appeared, polluted this region of the Solar System with no more than the gentle warmth of infrared radiation.

James Lovelock, Father of Gaia Theory, Endorses Natural Gas Fracking
By: Steve Maley
June 16th, 2012

James Lovelock, now 92 years of age, is the father of Gaia theory, the idea that Mother Earth is a sort of sentient, self-regulating organism. So it was noteworthy a few weeks back when he walked back some of his predictions of our planet’s impending doom from Global Warming.

In an interview with the Guardian, Lovelock embraces fracking for natural gas, scorns renewables and castigates the Germans for shutting down their nukes in favor of lignite, a low-grade coal, for electricity generation. (H/T wattsupwiththat.com.)

First, fracking:

Gas is almost a give-away in the US at the moment. They’ve gone for fracking in a big way. This is what makes me very cross with the greens for trying to knock it: the amount of CO2 produced by burning gas in a good turbine gives you 60% efficiency. In a coal-fired power station, it is 30% per unit of fuel. So you get a two-to-one gain there straight away. The next two-to-one gain you get is that methane has only got half its energy in the carbon, the other half is in the hydrogen, so there’s a four-to-one gain in CO2 output from the same amount of electricity by burning methane. Let’s be pragmatic and sensible and get Britain to switch everything to methane.

On renewables:

We rushed into renewable energy without any thought. The schemes are largely hopelessly inefficient and unpleasant. I personally can’t stand windmills at any price. Hydro, biomass, solar, etc, have all got great promise, but they’re not available tomorrow, or even in 10 years.

Germany:

Germany is a great country and has always been a natural leader of Europe, and so many great ideas, music, art, etc, come out of it, but they have this fatal flaw that they always fall for an ideologue and Europe has suffered intensely from the last two episodes of that. And it looks to me as if the green ideas they have picked up now could be just as damaging. They are burning lignite now to try and make up for switching off nuclear. They call themselves green, but to me this is utter madness.

The Intergovernmental Panel on Climate Change (IPCC):

I think the most outrageous example of climate scientists getting it wrong and not admitting it was the 2007 IPPC report. They happily accepted the Nobel prize, but their sea-level rise estimates … were 100% wrong. They didn’t really answer this other than say it’s a very complicated business and we’ve only just started. The IPCC is too politicised and too internalised. Whenever the UN puts its finger in it seems to become a mess.

-- www.redstate.com


In recent times, some interesting insights have come from the investigations of Ilya Prigogine and his colleagues into the thermodynamics of eddies, vortices, and many other transient systems that are low in entropy. Things like eddies and whirlpools develop spontaneously when there is a sufficient flux of free energy. It was in the nineteenth century that a British physicist, Osborne Reynolds, curious about the conditions that led to turbulence in the flow of fluids, discovered that the onset of eddies in a stream or in a flow of gas takes place only when the flow exceeds a critical value. A useful analogy here is that if you blow a flute too gently no sound emerges. But if you blow hard enough, wind eddies form and are made part of the system that makes sound. Extending the earlier mathematics of the American physical chemist Lars Onsager, Prigogine and his colleagues have applied the thermodynamics of the steady state to develop what might be called the thermodynamics of the "unsteady state." They classify these phenomena by the term "dissipative structures." They have structure, but not the permanency of solids; they dissipate when the supply of energy is turned off. Living organisms include dissipative structures within them, but the class is broadly based. It includes many manufactured things, such as refrigerators, and natural phenomena such as flames, whirlpools, hurricanes, and certain peculiar chemical reactions. Living things are so infinitely complex in comparison with the dissipative structures of the fluid state that many feel that, although on the right track, present-day thermodynamics has far to go in defining life. Physicists, chemists, and biologists, although not rejecting these notions, do not make them part of the inspiration of their working lives. Their response is like that of a wealthy congregation to the exhortations of their priest on the virtues of poverty. It is something felt to be good, but not a way of life for next week.

A crucial insight that comes from Schrodinger's generalizations about life is that living systems have boundaries. Living organisms are open systems in the sense that they take and excrete energy and matter. In theory, they are open as far as the bounds of the Universe; but they are also enclosed within a hierarchy of internal boundaries. As we move in towards the Earth from space, first we see the atmospheric boundary that encloses Gaia; then the borders of an ecosystem such as the forests; then the skin or bark of living animals and plants; further in are the cell membranes; and finally the nucleus of the cell and its DNA. If life is defined as a self-organizing system characterized by an actively sustained low entropy, then, viewed from outside each of these boundaries, what lies within is alive.

You may find it hard to swallow the notion that anything as large and apparently inanimate as the Earth is alive. Surely, you may say, the Earth is almost wholly rock and nearly all incandescent with heat. I am indebted to Jerome Rothstein, a physicist, for his enlightenment on this, and other things. In a thoughtful paper on the living Earth concept (given at a symposium held in the summer of 1985 by the Audubon Society) he observed that the difficulty can be lessened if you let the image of a giant redwood tree enter your mind. The tree undoubtedly is alive, yet 99 percent is dead. The great tree is an ancient spire of dead wood, made of lignin and cellulose by the ancestors of the thin layer of living cells that go to constitute its bark. How like the Earth, and more so when we realize that many of the atoms of the rocks far down into the magma were once part of the ancestral life from which we all have come.

When the Earth was first seen from outside and compared as a whole planet with its lifeless partners, Mars and Venus, it was impossible to ignore the sense that the Earth was a strange and beautiful anomaly. Yet this unconventional planet probably would have been kept in the scullery, like Cinderella, had not NASA in the role of Prince offered a rescue by way of the planetary exploration program. As we saw in chapter 1, the questions raised by space science were at first narrowly focused on a practical question: How is life on another planet to be recognized? Because that question could not be explained solely by conventional biology or geology, I became preoccupied with another question: What if the difference in atmospheric composition between the Earth and its neighbors Mars and Venus is a consequence of the fact that the Earth alone bears life?
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:25 pm

Part 2 of 2

The least complex and most accessible part of a planet is its atmosphere. Long before the Viking spacecraft landed on Mars, or the Russian Venera landed on Venus, we knew the chemical compositions of their atmospheres. In the middle 1960s, telescopes tuned to the infrared radiation reflected by the molecules of atmospheric gases were used to view Mars and Venus. These observations revealed the identity and proportion of the gases with fair accuracy. Mars and Venus both had atmospheres dominated by carbon dioxide, with only small proportions of oxygen and nitrogen. More important, both had atmospheres close to the chemical equilibrium state; if you took a volume of air from either of those planets, heated it to incandescence in the presence of a representative sample of rocks from the surface, and then allowed it to cool slowly, there would be little or no change in composition after the experiment. The Earth, by contrast, has an atmosphere dominated by nitrogen and oxygen. A mere trace of carbon dioxide is present, far below the expectation of planetary chemistry. There are unstable gases such as nitrous oxide, and gases such as methane that react readily with the abundant oxygen. If the same heating-and-cooling experiment were tried with a sample of the air that you are now breathing, it would be changed. It would become like the atmospheres of Mars and Venus: carbon dioxide dominant, oxygen and nitrogen greatly diminished, and gases such as nitrous oxide and methane absent. It is not too far-fetched to look on the air as like the gas mixture that enters the intake of an internal combustion engine: combustible gases, hydrocarbons, and oxygen mixed. The atmospheres of Mars and Venus are like the exhaust gases, all energy spent.

The amazing improbability of the Earth's atmosphere reveals negentropy and the presence of the invisible hand of life. Take for example oxygen and methane. Both are present in our atmosphere in constant quantities; yet in sunlight they react chemically to give carbon dioxide and water vapor. Anywhere you travel on the Earth's surface to measure it, the methane concentration is about 1.5 parts per million. Close to 1,000 million tons of methane must be introduced into the atmosphere annually to maintain methane at a constant level. In addition, the oxygen used in oxidizing the methane must be replaced -- at least 2,000 million tons yearly. The only feasible explanation for the persistence of this unstable atmosphere at a constant composition, and for periods vastly longer than the reaction times of its gases, is the influence of a control system, Gaia.

It is often difficult to recognize the larger entity of which we are a part; as the saying goes, "You can't see the forest for the trees." So it was with the Earth itself before we shared with the astronauts vicariously that stunning and awesome vision; that impeccable sphere that punctuates the division of the past from the present. This gift, this ability to see the Earth from afar, was so revealing that it forced the novel top-down approach to planetary biology. The conventional wisdom of biology on Earth itself had always been forced to take a bottom-up approach by the sheer size of the Earth when compared with us or any living thing we knew. The two approaches are complementary. In the understanding of a microbe, an animal, or a plant, the top-down physiological view of life as a whole system harmoniously merges with the bottom-up view originating with molecular biology: that life is an assembly made from a vast set of ultramicroscopic parts.

Since James Hutton there has been a "loyal opposition" of scientists who doubted the conventional wisdom that the evolution of the environment is determined by chemical and physical forces alone. Vernadsky adopted Suess's concept of the biosphere to define the boundaries of the realm of the biota. Since Vernadsky, there has been a continuous tradition (called biogeochemistry) in the Soviet Union -- and, to a lesser extent, elsewhere -- that has recognized the interaction between the soils, oceans, lakes, and rivers and the life they bear. It is well stated by a Russian, M. M. Yermolaev, in An Introduction to Physical Geography: "The biosphere is understood as being that part of the geographical envelope of the Earth, within the boundaries of which the physico-geographical conditions ensure the normal work of the enzymes." More recent members of this scientific opposition have included the following: Alfred Lotka of John Hopkins University, and Eugene Odum, who alone among ecologists took a physiological view of ecosystems; two Americans of European origin, the limnologist G. Evelyn Hutchinson and the paleontologist Heinz A. Lowenstam; an oceanographer from Britain, A. Redfield; and a Swedish geochemist, L. G. Sillen. They all have recognized the importance of the participation by life in the evolution of the environment. Most geologists, however, have neglected the presence of living organisms as an active participant in their theories of the Earth's evolution.

The counterpart of this geological apartheid is the failure of most biologists to recognize that the evolution of the species is strongly coupled with the evolution of their environment. For example, in 1982 there appeared a book, Evolution Now: A Century after Darwin, edited by John Maynard Smith, which consisted of a collection of essays by distinguished biologists on the most controversial issues of evolutionary biology. In this collection, the only (and enigmatic) mention of the environment is in an essay by Stephen Jay Gould: "Organisms are not billiard balls, struck in a deterministic fashion by the cue of natural selection and rolling to optimal positions on life's table. They influence their own destiny in interesting and complex and comprehensible ways. We must put this concept of organism back into evolutionary biology."

Apart from Lynn Margulis, the only other biologist I know to have taken the environment into account when considering life is J. Z. Young. In 1971, this distinguished physiologist was independently moved to write in a chapter on homeostasis in his book, An Introduction to the Study of Man: "The entity that is maintained intact, and of which we all form a part, is not the life of one of us, but in the end the whole of life upon the planet." J. Z. Young's view serves as a link between Gaia theory and the general scientific consensus. Through Gaia theory, I see the Earth and the life it bears as a system, a system that has the capacity to regulate the temperature and the composition of the Earth's surface and to keep it comfortable for living organisms. The self-regulation of the system is an active process driven by the free energy available from sunlight.

The early reaction, soon after the Gaia hypothesis was introduced in the early 1970s, was ignorance in the literal sense. For the most part the Gaian idea was ignored by professional scientists. It was not until the late 1970s that it was subjected to criticism.

Good criticism is like bathing in an ice-cold sea. The sudden chill of immersion in what seems at first a hostile medium soon stirs the blood and sharpens the senses. My first reaction on reading W. Ford Doolittle's criticism of the Gaia hypothesis in CoEvolution Quarterly in 1979 was shock and incoherent disbelief. The article was splendidly put together and beautifully written, but this did not lessen its frigidity. Icy waters may be pellucid, but this does not make them warm. After an icy plunge, however, comes that warm sense of relaxation when sunning on the beach. After a while, I began to realize that Ford Doolittle's criticism could be taken not so much as an attack on Gaia but as a criticism of the inadequacy of its presentation.

Gaia had first been seen from space and the arguments used were from thermodynamics. To me it was obvious that the Earth was alive in the sense that it was a self-organizing and self-regulating system. To Ford Doolittle, from his world of molecular biology, it was equally obvious that evolution by natural selection could never lead to "altruism" on a global scale. He was supported in the similarly forceful and effective writings of Richard Dawkins in his book, The Extended Phenotype (1982). From their world of microscopes, how could the "selfish" interests of living cells be expressed at the distance of a planet? For these competent and dedicated biologists, positing the regulation of the atmosphere by microbial life seemed as absurd as expecting the legislation of some human government to affect the orbit of Jupiter. I am indebted to them both for having shown clearly that we were taking far too much for granted, and that Gaia lacked a firm theoretical basis.

Not only did molecular biologists object to Gaia. Two other valued critics were the climatologist Stephen Schneider from Colorado, and the geochemist H. D. Holland from Harvard. They, in common with most of their peers, preferred to explain the facts of the evolution of the rocks, the ocean, the air, and the climate by chemical and physical forces alone. In his book The Chemical Evolution of the Atmosphere and the Oceans, Holland wrote: "I find the hypothesis intriguing and charming, but ultimately unsatisfactory. The geologic record seems much more in accord with the view that the organisms that are better able to compete have come to dominate, and that the Earth's near surface environment and processes have accommodated themselves to changes wrought by biological evolution. Many of these changes must have been fatal or near fatal to parts of the contemporary biota. We live on an Earth that is the best of all worlds but only for those who have adapted to it." Stephen Schneider's objection -- expressed in his book with Randi Londer, The Coevolution of Climate and Life -- was to the implication in the early papers on Gaia that homeostasis was the only means of climate regulation. I am indebted to all of these critics for having shown clearly that we were taking too much for granted, and that Gaia lacked a firm theoretical basis. Greater than this is my gratitude to Stephen Schneider who made sure that Gaia was properly debated by the scientific community by calling a Chapman Conference of the American Geophysical Union in March 1988.

How in the world could the bacteria, the trees, and the animals have a conference to decide optimum conditions? How could organisms keep oxygen at 21 percent and the mean temperature at 20°C? Not seeing a mechanism for planetary control, they denied its existence as a phenomenon and branded the Gaia hypothesis as teleological. This was a final condemnation. Teleological explanations, in academe, are a sin against the holy spirit of scientific rationality; they deny the objectivity of Nature.

A teleological or design argument is an a posteriori argument for the existence of God based on apparent design and purpose in the universe. The argument is based on an interpretation of teleology wherein purpose and design appear to exist in nature beyond the scope of any such human activities. The teleological argument suggests that, given this premise, the existence of a designer can be assumed, typically presented as God. Various concepts of teleology originated in ancient philosophy and theology. Some philosophers, such as Plato, proposed a divine Artificer as the designer; others, including Aristotle, rejected that conclusion in favor of a more naturalistic teleology.

In the Middle Ages, the Islamic philosopher Averroes introduces a teleological argument. Later, a teleological argument is the fifth of Saint Thomas Aquinas' Five Ways, his rational proofs for the existence of God. The teleological argument was continued by empiricists in the seventeenth and eighteenth centuries, who believed that the order in the world suggested the existence of God. William Paley developed these ideas with his version of the watch maker analogy. He argued that in the same way a watch's complexity implies the existence of its maker, so too one may infer the Creator of the universe exists, given the evident complexity of Nature. This argument resonates with a notion of the fine-tuned Universe, understood as an alternative to the anthropic principle.

Many philosophers and theologians have expounded and criticized different versions of the teleological argument. Commonly, they argue that any implied designer need not have the qualities commonly attributed to the God of classical theism. Scientists have shown alternative explanations for biological complexity, notably natural selection, with no requirement for supernatural design. From the 1990s, neo-creationism and intelligent design have presented the teleological argument while avoiding naming the designer with the aim of presenting this as science and getting it taught in public school science classes. In 2005, a U.S. Federal Court ruled that intelligent design is a religious argument and is not science, and was being used to give pseudoscientific support for creationism, the religious belief in a designer.

-- Teleological Argument, by Wikipedia


But when making this severest of criticisms of Gaia, the scientists may not have noticed the extent of their own errors. The innocent use of that slippery concept "adaptation" is another path to damnation. Earth is indeed the best of all worlds for those who are adapted to it. But the excellence of our planet takes on a different significance in the light of the evidence that geochemists themselves have gathered. Evidence that shows the Earth's crust, oceans, and air to be either directly the product of living things or else massively modified by their presence. Consider how the oxygen and nitrogen of the air come directly from plants and microorganisms, and how the chalk and limestone rocks are the shells of living things once floating in the sea. Life has not adapted to an inert world determined by the dead hand of chemistry and physics. We live in a world that has been built by our ancestors, ancient and modern, and which is continuously maintained by all things alive today. Organisms are adapting in a world whose material state is determined by the activities of their neighbors; this means that changing the environment is part of the game. To think otherwise would require that evolution was a game with rules like cricket or baseball -- one in which the rules forbad environmental change. If, in the real world, the activity of an organism changes its material environment to a more favorable state, and as a consequence it leaves more progeny, then both the species and the change will increase until a new stable state is reached. On a local scale adaptation is a means by which organisms can come to terms with unfavorable environments, but on a planetary scale the coupling between life and its environment is so tight that the tautologous notion of "adaptation" is squeezed from existence. The evolution of the rocks and the air and the evolution of the biota are not to be separated.

It is a tribute to the success of biogeochemistry that most Earth scientists today agree that the reactive gases of the atmosphere are biological products. But most would disagree that the biota in any way control the composition of the atmosphere, or any of the important variables, such as global temperature and oxygen concentration, which depend on the atmosphere. There are two principal objections to Gaia, first that it is teleological, and that for the regulation of the climate, the chemical composition on a planetary scale, a kind of forecasting, a clairvoyance, would be needed. The second objection, most clearly expressed by Stephen Schneider, is that biological regulation is only partial, and that the real world is a "coevolution" of life and the inorganic. The second criticism is the more difficult, and in many ways the purpose of this book is to try to answer it. The first, the teleological criticism, I think is wrong and I will now try to show why.

I knew that there was little point in gathering more evidence about the now-obvious capacity of the Earth to regulate its climate and composition. Mere evidence by itself could not be expected to convince mainstream scientists that the Earth was regulated by life. Scientists usually want to know how it works; they want a mechanism. What was needed was a Gaian model. In those hybrid sciences of biogeochemistry and biogeophysics, models of environmental change do not permit a regulatory role to the biota. The practitioners of these sciences assume that the operating points of the system are fixed by chemical and physical properties. For example, snow melts or forms at 0°C. The reflection of sunlight by snow cover can provide a powerful positive feedback on cooling, and a system for regulating the climate could be based on the melting or formation of snow. But there is no way for the melting point of snow, which is a characteristic of ice as a substance, to change to a more comfortable warmth of, say, 20°C. In great contrast, the operating points of a living organism are always set at favorable levels.

In what way do Gaian models differ from the conventional biogeochemical ones? Does the assumption of the close coupling of life and its environment change the nature of the whole system? Is homeostasis a reasonable prediction of Gaia theory? The difficulty in answering these questions comes from the sheer complexity of the biota and the environment, and because they are interconnected in multiple ways. There is hardly a single aspect of their interaction that we can confidently describe by a mathematical equation. A drastic simplification was needed. I wrestled with the problem of reducing the complexity of life and its environment to a simple scheme that could enlighten without distorting. Daisyworld was the answer. I first described this model in 1982 at a conference on biomineralization in Amsterdam, and published a paper, "The Parable of Daisyworld," in Tellus in 1983 with my colleague Andrew Watson. I am indebted to Andrew for the clear, graphic way of expressing it in formal mathematical terms in this paper.

Picture a planet about the same size as the Earth, spinning on its axis and orbiting, at the same distance as the Earth, a star of the same mass and luminosity as the Sun. This planet differs from the Earth in having more land area and less ocean, but it is well watered, and plants will grow almost anywhere on the land surfaces when the climate is right. This is the planet Daisyworld, so called because the principal plant species are daisies of different shades of color: some dark, some light, and some neutral colors in between. The star that warms and illuminates Daisyworld shares with our Sun the property of increasing its output of heat as it ages. When life started on Earth some 3.8 billion years ago, the Sun was about 30 percent less luminous than now. In a few more billion years, it will become so fiercely hot that all life that we know will die or be obliged to find another home planet. The increase of the Sun's brightness as it ages is a general and undoubted property of stars. As the star bums hydrogen (its nuclear fuel) helium accumulates. The helium, in the form of a gaseous ash, is more opaque to radiant energy than is hydrogen and so impedes the flow of heat from the nuclear furnace at the center of the star. The central temperature then rises and this in turn increases the rate of hydrogen burning until there is a new balance between heat produced at the center and the heat lost from the solar surface. Unlike ordinary fires, star-sized nuclear fires burn fiercer as the ash accumulates and sometimes even explode.

Daisyworld is simplified, reduced if you like, in the following ways. The environment is reduced to a single variable, temperature, and the biota to a single species, daisies. If too cold, below 5°C, daisies will not grow; they do best at a temperature near 20°C. If the temperature exceeds 40°C, it will be too hot for the daisies, and they will wilt and die. The mean temperature of the planet is a simple balance between the heat received from the star and the heat lost to the cold depths of space in the form of long-wave infrared radiation. On the Earth, this heat balance is complicated by the effects of clouds and of gases such as carbon dioxide. The sunlight may be reflected back to space by the clouds before it can reach and warm the surface. On the other hand, the heat loss from the warm surface may be lessened because clouds and molecules of carbon dioxide reflect it back to the surface. Daisyworld is assumed to have a constant amount of carbon dioxide, enough for daisies to grow but not so much as to complicate the climate. Similarly, there are no clouds in the daytime to mar the simplicity of the model, and all rain falls during the night.

The mean temperature of Daisyworld is, therefore, simply determined by the average shade of color of the planet, or as astronomers call it, the albedo. If the planet is a dark shade, low albedo, it absorbs more heat from the sunlight and the surface is warmed. If light in color, like fallen snow, then 70 or 80 percent of the sunlight may be reflected back to space. Such a surface is cold when compared with a dark surface under comparable solar illumination. Albedos range from 0 (wholly black) to 1 (wholly white). The bare ground of Daisyworld is usually taken to have an albedo of 0.4 so that it absorbs 40 percent of the sunlight that falls upon it. Daisies range in shade of color from dark (with an albedo of 0.2) to light (with an albedo of 0.7).

According to the alchemists, the Work begins by finding a substance called the prima materia (which some believe to be salt, some mercury, others earth of even water). This must be pulverized, mixed with a 'secret fire', and heated in a sealed vessel. This prima materia contains two elements, male and female, referred to as sol and luna, or sulphur and mercury. In the sealed vessel, these blacken and putrefy, a process known as the 'nigredo'. Then the mass should begin to show white flecks, and to turn white -- a process known as the albedo. It becomes volatile, and recrystallizes as a white stone. In this stone, the male and female elements are united into a 'mysterium coniunctionis' or marriage, and it is capable of healing. At the next stage of the process, the white stone is added to 'mercury', and an obscure process known as 'exaltation' takes place. The stone turns green after being dissolved in acid -- a stage known as the green lion -- and finally turns red. This is the Philosopher's Stone, which can turn base metals into gold, and which is also the Elixir of Life.

-- C. G. Jung: Lord of the Underworld, by Colin Wilson


Imagine a time in the distant past of Daisyworld. The star that warms it was less luminous, so that only in the equatorial region was the mean temperature of bare ground warm enough, 5°C, for growth. Here daisy seeds would slowly germinate and flower. Let us assume that in the first crop multicolored, light, and dark species were equally represented. Even before the first season's growth was over, the dark daisies would have been favored. Their greater absorption of sunlight in the localities where they grew would have warmed them above 5°C. The light-colored daisies would be at a disadvantage. Their white flowers would have faded and died because, reflecting the sunlight as they do, they would have cooled below the critical temperature of 5°C.

The next season would see the dark daisies off to a head start, for their seeds would be the most abundant. Soon their presence would warm not just the plants themselves, but, as they grew and spread across the bare ground, would increase the temperature of the soil and air, at first locally and then regionally. With this rise of temperature, the rate of growth, the length of the warm season, and the spread of dark daisies would all exert a positive feedback and lead to the colonization of most of the planet by dark daisies. The spread of dark daisies would eventually be limited by a rise of global temperature to levels above the optimum for growth. Any further spread of dark daisies would lead to a decline in seed production. In addition, when the global temperature is high, white daisies will grow and spread in competition with the dark ones. The growth and spread of white daisies is favored then because of their natural ability to keep cool.

As the star that shines on Daisyworld grows older and hotter, the proportion of dark to light daisies changes until, finally, the heat flux is so great that even the whitest daisy crop cannot keep enough of the planet below the critical 40°C upper limit for growth. At this time flower power is not enough. The planet becomes barren again, and so hot that there is no way for daisy life to start again.

It is easy to make a numerical model of Daisyworld simple enough to run on a personal computer. Daisy populations are modeled by differential equations borrowed from theoretical ecology (Carter and Prince, 1981). The mean temperature of the planet is calculated directly from the balance of the heat it receives from its star and the heat it loses by radiation to the cold depths of space. Figure 2.1 shows the evolution of the temperature and the growth of daisies during the progressive increase in heat flux from its star according to the conventional wisdom of physics and biology, and according to geophysiology.

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Solar luminosity Solar luminosity
2.1 Models of the evolution of Daisyworld according to conventional wisdom (A) and to geophysiology (B). The upper panels illustrate daisy populations in arbitrary units; the lower panels, temperatures in degrees Celsius. Going from left to right along the horizontal axis, the star's luminosity increases from 60 to 140 percent of that of our own Sun. A illustrates how the physicists and the biologists in complete isolation calculate their view of the evolution of the planet. According to this conventional wisdom, the daisies can only respond or adapt to changes in temperature. When it becomes too hot for comfort, they will die. But in the Gaian Daisyworld (B), the ecosystem can respond by the competitive growth of the dark and light daisies, and regulate the temperature over a wide range of solar luminosity. The dashed line in the lower panel in B shows how the temperature would rise on a lifeless Daisyworld.

When I first tried the Daisyworld model I was surprised and delighted by the strong regulation of planetary temperature that came from the simple competitive growth of plants with dark and light shades. I did not invent these models because I thought that daisies, or any other dark- and light-colored plants, regulate the Earth's temperature by changing the balance between the heat received from the Sun and that lost to space. I had designed them to answer the criticism of Ford Doolittle and Richard Dawkins that Gaia was teleological. In Daisyworld, one property of the global environment, temperature, was shown to be regulated effectively, over a wide range of solar luminosity, by an imaginary planetary biota without invoking foresight or planning. This is a definitive rebuttal of the accusation that the Gaia hypothesis is teleological, and so far it remains unchallenged.

So what is Gaia? If the real world we inhabit is self-regulating in the manner of Daisyworld, and if the climate and environment we enjoy and freely exploit is a consequence of an automatic, but not purposeful, goal-seeking system, then Gaia is the largest manifestation of life. The tightly coupled system of life and its environment, Gaia, includes:

1. Living organisms that grow vigorously, exploiting any environmental opportunities that open.

2. Organisms that are subject to the rules of Darwinian natural selection: the species of organisms that leave the most progeny survive.

3. Organisms that affect their physical and chemical environment. Thus animals change the atmosphere by breathing: taking in oxygen and letting out carbon dioxide. Plants and algae do the reverse. In numerous other ways, all forms of life incessantly modify the physical and chemical environment.

4. The existence of constraints or bounds that establish the limits of life. It can be too hot or too cold; there is a comfortable warmth in between, the preferred state. It can be too acid or too alkaline; neutrality is preferred. Almost all chemicals have a range of concentrations tolerated or needed by life. For many elements, such as iodine, selenium, and iron, too much is a poison, too little causes starvation. Pure uncontaminated water will support little; but neither will the saturated brine of the Dead Sea.

Few scientists would object to any of these four conditions, either singly or taken as a group. When they are taken together as a tightly coupled ensemble, they seem to form a recipe for a Gaian system. The ensemble is a fruitful source of models of self-regulating systems like Daisyworld. The fourth condition, which sets the physical and chemical bounds of life, I find the most interesting, unexpected, and full of insight. One has only to think of the social analogue of the family or community that exists with firm but reasonable bounds in comparison with one in which the limits of behavior are ill-defined. Stability and well-defined bounds seem to go together. Physicists are agreed that life is an open system. But like one of those Russian dolls which enclose a series of smaller and still smaller dolls, life exists within a set of boundaries. The outer boundary is the Earth's atmospheric edge to space. Within the planetary boundary, entities diminish but grow ever more intense as the inward progression goes from Gaia to ecosystems, to plants and animals, to cells and to DNA. The boundary of the planet then circumscribes a living organism, Gaia, a system made up of all the living things and their environment. There is no clear distinction anywhere on the Earth's surface between living and nonliving matter. There is merely a hierarchy of intensity going from the "material" environment of the rocks and the atmosphere to the living cells. But at great depths below the surface, the effects of life's presence fade. It may be that the core of our planet is unchanged as a result of life; but it would be unwise to assume it.

In exploring the question, "What is life?" we have made some progress. By looking at life through Gaia's telescope, we see it as a planetary-scale phenomenon with a cosmological life span. Gaia as the largest manifestation of life differs from other living organisms of Earth in the way that you or I differ from our population of living cells. At some time early in the Earth's history before life existed, the solid Earth, the atmosphere, and oceans were still evolving by the laws of physics and chemistry alone. It was careering, downhill, to the lifeless steady state of a planet almost at equilibrium. Briefly, in its headlong flight through the ranges of chemical and physical states, it entered a stage favorable for life. At some special time in that stage, the newly formed living cells grew until their presence so affected the Earth's environment as to halt the headlong dive towards equilibrium. At that instant the living things, the rocks, the air, and the oceans merged to form the new entity, Gaia. Just as when the sperm merges with the egg, new life was conceived.

The quest to define life might be compared with assembling a jigsaw puzzle, a puzzle where a landscape scene is cut into a thousand small interlocking pieces and the pieces scrambled. Classification is needed to put it together again. The blue sky is easy to separate from the brown earth and green trees. Skilled solvers of the jigsaw puzzle know that a key step is to find and connect the straight-sided pieces that define the edge, the boundary of the scene. The discovery that the outer reaches of the atmosphere are a part of planetary life in a like manner has defined the edge of our puzzle picture of the Earth. Once the edge is completely assembled, at least the size of the picture is known and the placing of the inner groupings made easier. Gaia is no static picture. She is forever changing as life and the Earth evolve together, but in our brief life span she keeps still long enough for us to begin to understand and see how fair she is.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:28 pm

3: Exploring Daisyworld

Give me a fruitful error any time, full of seeds, bursting with its own corrections.

-- Vilfredo Pareto, comment on Kepler


The word theory has the same Greek root as theatre. Both are concerned with putting on a show. A theory in science is no more than what seems to its author a plausible way of dressing up the facts and presenting them to the audience. Like plays, theories are judged according to several different, and barely connected, criteria. Artistic content is important; a theory that is elegant, inspiring, and presented with craftsmanship is universally appreciated. But hard-working scientists like best theories that are full of predictions which can easily be tested. It matters little whether the view of the theorizer is right or wrong: investigation and research are stimulated, new facts discovered, and new theories composed. That it was wrong did little to detract from the theory of continuous creation put forward by the astronomers Hoyle, Bondi, and Gold. It has now been abandoned, but in its day it was a deeply satisfying intellectual concept. The only bad theories are those that cannot be questioned or tested. What use is a theory that the Universe was created, complete with inhabitants, and all with memories of a non-existent past, at 15.37 hr GMT on October 27, 1917? There is no way to prove or disprove it, and it makes no useful predictions.

At first glance, Gaia theory might seem to be untestable. Obviously, it would be improper and irresponsible to attempt vivisection on a whole living planet. The nineteenth-century "blood up to the elbows" school of investigating living things is passe. We have learnt from engineers, who value their contraptions more than most of us value the infinitely more complex and beautiful mechanisms of living organisms, that so much can be learnt from the noninvasive testing of a system that vivisection is not needed. In many different ways, Gaia theory is wide open for experimental investigation.

The most direct evidence comes from the real world as it now is. Just as we can observe the pulse, the blood pressure, the electrical activity of the heart, and so on without interfering with the normal physiology of a human subject; so we can observe the circulation of air, the oceans, and the rocks. We can measure the seasonal pulsing of the carbon dioxide of the air as the plants breathe it in and the consumers breathe it out. We can follow the course of essential nutrients from the rocks to the ocean to the air and back again, and see how at each step different but interlinked systems are affected.

There is also a vast amount of historical evidence preserved in the rocks. During its life span, our planet has suffered the impact of planetesimals. We have been hit by close to thirty small planets, up to 10 miles in diameter and traveling as fast as sixty times the speed of sound. These impacts release about a thousand times as much energy as would be released if all the nuclear powers exploded all the present weapon stocks. Such events do more than make 200-mile craters, they can destroy up to 90 percent of all living organisms from the microscopic to the macroscopic. The impacts make the Earth ring like a bell, and the reverberations of the event resonate, metaphorically, throughout the systems of the Earth for maybe a million years or more. The history of our planet is punctuated by these perturbations; from their record we can learn a great deal about how the system works and the way that homeostasis is fully restored. Should you doubt that the Earth has been so stricken so often, glance at the map of the distribution of craters on the older surface rocks in Canada (figure 3.1). It is like a glance at a region of the Moon's surface. On most of the continental areas and on all the surface of the sea floor, however, the rapidity of the smoothing processes of weathering and sea-floor spreading rapidly remove the evidence of any but the most recent impacts.

Image
3.1 Map of Canada showing large meteor craters.

Not all catastrophic events are from external causes; some, such as the appearance of oxygen gas, are generated by inherent internal contradictions within the system and can be likened to such crises in living organisms as puberty, menopause, or the metamorphosis of a pupa to a butterfly. The record of the rocks, though blurred by time and often incomplete, still preserves some evidence of the chemical and physical state of the Earth and of the distribution of the species before and after each of these perturbations. But disentangling the record is rather like trying to find traces of the identity of a terrorist from the rubble of the building his bomb destroyed.

The most persuasive criticism of Gaia theory is that planetary homeostasis, by and for living organisms, is impossible because it would require the evolution of communication between the species and a capacity for foresight and planning. The critics who made this challenging, and to me helpful, criticism were not concerned with the practical evidence that the Earth has kept a climate favorable for life in spite of major perturbations, or that the atmosphere is now stable in its composition in spite of the chemical incompatibility of its component gases. They were criticizing from the certainty of their knowledge of biology. No organism as large, and, as they saw her, sentient, could possibly exist. I think this criticism is dogmatic, and, as we saw in the last chapter, it is easy to answer. The simple model Daisyworld illustrated how Gaia might work. It pictured an imaginary world that spun like the Earth as it circled and was warmed by a star that was the identical twin of our own Sun. On this world, the competition for territory between two species of daisies, one dark and one light in color, led to the accurate regulation of planetary temperature close to that comfortable for plants like daisies. No foresight, planning, or purpose was invoked. Daisyworld is a theoretical view of a planet in homeostasis. We can now begin to think of Gaia as a theory, something rather more than the mere "let's suppose" of an hypothesis.

There is much more to Daisyworld than just the answer to a criticism. I first made it for that purpose, but as it has developed I have found it to be a source of insight and an answer to questions about theoretical ecology and Darwinism, as well as to questions about Gaia. An important property of the model is its docility and stability in mathematical terms. As I continue to work with these models I find that the number of species that can be accommodated appears to be limited only by the speed and capacity of the computer used and by my patience. Whatever the details, the inclusion of feedback from the environment appears to stabilize the system of differential equations used to model the growth and competition of the species. Most of what follows is the record of my explorations in Daisyworld and an account of the discoveries there. I have assumed that many of my readers are not moved by mathematical expressions, and have therefore not included these. For those who regard any theory not expressed in the pure language of mathematics as at best inadequate, Andrew Watson and I have described the mathematics of Daisyworld in our paper in Tellus. In no way is the stability of Daisyworld dependent upon an idiosyncratic choice of initial values, or rate constants, and as we shall see in later chapters the model is general in its application.

It may still be that some of the diagrams used to illustrate the geophysiology of the model planet are difficult to follow for readers unfamiliar with this form of graphic explanation. For you, I have written this book so that this chapter can be skipped without much loss, provided that you are already convinced that Gaia theory gives a fair representation of the Earth. But I ask my critics to read on, for here I shall try to answer in detail the objections they have raised.

The reaction of scientists to the Daisyworld model was revealing. Meteorologists and climatologists were the most interested; geologists and geochemists next. With rare exceptions, biologists either ignored the models or remained as skeptical as ever. A persistent criticism from biologists was that, in a real world, daisies would have to use some of their energy to make pigment and therefore would be at a disadvantage compared with unpigmented gray daisies. In such a world no temperature regulation would take place. As they put it, "the gray daisies would cheat."

Stimulated by their criticism I made a model with three species of daisies. All that the new model required was another set of equations to describe the temperature and growth of the gray daisy species. It was a matter of introducing sober-suited middle-management daisies to a world of colorful eccentrics. I charged the dark and light daisies a 1 percent growth-rate tax to make pigments. I am pleased to report that the biologists' cynical view of the world is not supported by this new model, as you can see from the results in figure 3.2. Again, the solar luminosity increases from 60 to 140 percent of that of our own Sun. The populations of the daisies are on the upper panel, with dark on the left, gray in the middle, and light on the right. The fact that gray daisies use no energy to make pigment avails them of nothing when their world is too hot or too cold for them to grow. But dark daisies can flourish in the cold, and white ones in the hot. Gray daisies do best when the climate is temperate and when regulation is not needed. In other words, the different species grow when they and their environment are fit for one another.

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Solar luminosity
3.2 The evolution of the climate on a three-species Daisyworld with dark, gray, and light daisies present. By comparison, the dashed line in the lower panel represents the temperature evolution in the absence of life.


It would have been sufficient as an answer to the critics merely to have added gray daisies, but having started, I found that it was almost as easy to make a model that would accommodate any number of daisies from one to twenty. I therefore did this, constructing the model so that, whatever the number of species, the shade of the daisies varied in constant steps going from dark to light. Figure 3.3 illustrates the evolution of temperature, daisy population, and other properties of a world with twenty species of daisies. Like the three-species model, it is of a world whose star grows hotter as it ages. The lower panel shows the evolution of the planetary temperature, the middle panel the evolution of the populations of the different species, and the upper panel the total biomass and the diversity of the ecosystem represented in the model. The diversity of the ecosystem is greatest when there is the least stress. When the heat from the Sun is just right for growth and no effort is required for temperature regulation, then the greatest number of species can coexist. When the system is under stress, when it has just begun to evolve or is about to die, then diversity is least and the population is almost entirely made up of the darkest or the lightest species. Indeed, if any species is at an advantage at such times, it is the darkest or the lightest, not the gray.

But there is much more to this new model than an answer to the criticisms of skeptical biologists. When I made it I was ignorant of theoretical ecology, that branch of mathematical biology that is concerned with interactions among the species of an ecosystem. As we shall see, Daisyworlds provide an escape for a science that has been trapped for years by the limitations of its theories.

In the 1920s, the mathematical biologists Lotka and Volterra introduced their famous model of the competition between rabbits and foxes. Like Daisyworld it was a simple model, but it differed in that the environment was taken as infinite and neutral. The growth of the populations of rabbits or foxes did not affect the environment, and no environmental changes were allowed to affect the rabbit and fox populations. The two equations for this world can be expressed in words as follows: Foxes increase as the numbers of rabbits grow, but rabbits decline as the foxes increase. In this relationship, there is one stable point where the two species coexist at a constant ratio. But one bad season that kills off some rabbits, indeed any change in population other than from the model itself, dooms this simple world to cyclical fluctuation from which it can never return to the stable ratio. Note how this happens. If a plague causes a sudden death of rabbits, this will be followed by the death of foxes from starvation. Rabbits breed fast, and soon their numbers are up to and beyond those before the plague. But now foxes begin to increase also, and the rate of rabbit growth slows and then declines as a surfeit of foxes culls them. Soon there are too few rabbits to feed the foxes, the foxes die, and the cycle begins anew.

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Solar luminosity
3.3 The evolution of the climate on a 20-species Daisyworld. The lower panel illustrates planetary temperature -- the dashed curve with no life present, and the solid line with daisies. The middle panel shows the populations of the 20 different colored daisies, with the darkest appearing first (left) and the lightest last (right). The upper panel illustrates diversity, seen to be maximum when the system temperature is closest to optimum.


Does this model world account for observed population swings in Nature? Yes, it does. Field ecologists have shown that population cycles do occur in simple ecosystems, but when we look closer, it seems that the field observations are almost always chosen from diseased or man-made ecosystems where few major species are present and interacting, and when only two of the species are considered (for example, pests attacking the vegetation of an agricultural monoculture, or bacterial disease among plants and animals). In these two-species examples, the populations either cycle periodically or fluctuate in a chaotic and unpredictable manner, and can be successfully modeled by the mathematical successors of Lotka and Volterra's famous fox and rabbit model. What these ecological models and theoretical ecology as a science have so far been unable to explain is the great stability of natural complex ecosystems like the tropical forests or Darwin's tangled bank: "Whereon the wild thyme blew and oxlips and the nodding violet grew."

Ecologists have attempted to overcome the inadequacies of their simple models by including a structured hierarchy of species that are referred to as "food webs." In such a hierarchy there is a pyramid that is surmounted by the top predator, such as a lion, with the smallest numbers. The numbers increase as you go down each "trophic" level, until at the base of the pyramid are the most numerous primary producers, the plants, that provide food for the whole system. In spite of years of effort and computer time, the ecologists have made no real progress towards modeling a complex natural ecosystem such as a tropical rain forest or the three-dimensional ecosystem of the ocean. No models drawn from theoretical ecology can account in mathematical terms for the manifest stability of these vast natural systems.

Indeed, a distinguished ecologist, Robert May, in his book Theoretical Ecology, writes in a chapter entitled "Patterns in Multispecies Ecosystems":

When these kinds of studies are made, a wide variety of mathematical models suggest that as a system becomes more complex, in the sense of more species and a more rich structure of interdependence, it becomes more dynamically fragile.... Thus, as a mathematical generality, increasing complexity makes for dynamical fragility rather than robustness.


May goes on to write:

This is not to say that, in Nature, complex ecosystems need appear less stable than simple ones. A complex system in an environment characterized by a low level of random fluctuation and a simple system in an environment characterized by a high level of random fluctuation can well be equally likely to persist, each having the dynamic stability appropriate to its environment.... An important general conclusion is that large and unprecedented perturbations imposed by man are likely to be more traumatic for complex ecosystems than for simple ones. This inverts the naive, if well intentioned, view that "complexity begets stability" and its accompanying moral that we should preserve, or even create, complex systems as buffers against man's importunities. I would argue that the complex natural ecosystems currently under siege in the tropics and subtropics are less able to withstand our battering than are the relatively simple temperate and boreal systems.


This disclaimer recognizes the stability of complex ecosystems in the real world; but the impression remains that diversity is, in general, a disadvantage and that Nature, by disregarding the elegant mathematics of theoretical biology, has somehow cheated.

Obviously, had I known of this work, I would never have attempted anything so foolish as a model with twenty daisies. Fortunately for me I was brought up in that school of science that believes in reading the books after rather than before an experiment. What is it, then, that confers the great stability and freedom from cyclical and chaotic behavior on the Daisy' world models? The answer is that in Daisyworld the species can never grow uncontrollably; if they do, the environment becomes unfavorable and growth is curtailed. Similarly, while daisies live, the physical environment cannot move to unfavorable states; the responsive growth of the appropriately colored daisy prevents it. It is the close coupling of the relationships which constrain both daisy growth and planetary temperature that makes the model behave. Perhaps it is a metaphor for our own experience that the family and society do better when firm, but justly applied, rules exist than they do with unrestricted freedom.

Curious to see if this explanation was correct, I made an additional Daisyworld. In this one, the daisies were grazed by rabbits and the rabbits in turn eaten by foxes -- a combination of Lotka and Volterra's model with Daisyworld. To test the stability of this more complex model, I subjected it to periodic catastrophes; on four occasions during the evolution of the model 30 percent of the daisy population was destroyed suddenly as by a plague, and the system then allowed to recover (see figure 3.4). Remarkably, neither the addition of herbivores nor plagues seriously affects the capacity of the daisies to regulate climate. During the normal course of evolution all populations are stable and recover promptly from the perturbations of the plagues. Eventually, the system can no longer cope with the ever-increasing solar output and it fails. As one might expect, the nearer to failure the greater the effect of the perturbations.

The difference between the geophysiological and the ecological view is in the interpretation of perturbation. The geophysiologists see temperature, rainfall, the supply of nutrients, and so on as variables that might be perturbed. In their view the Gaian system evolved with its physical and chemical environment and is well able to resist changes of this kind. Forests of the humid tropics are normally well watered and shaded by their canopy of clouds; during their existence they are never subjected to prolonged drought as in a desert region. Theoretical ecologists, on the other hand, ignore the physical and chemical environment; to them the environment means the collection of species themselves and a niche is some piece of territory negotiated among the species, rather as one might regard the environment of Switzerland as comprising the people of Italy, France, and Germany. In such a view, perturbations are competition or wars.

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Solar luminosity
3.4 Daisyworld with rabbits and faxes, perturbed by four plagues that killed 30 percent of the daises.


The invasion of a tropical forest by humans with chain saws who would replace it with an agricultural ecosystem is a traumatic act. It is like destroying the ecosystem of the model with twenty species and replacing it with a monoculture of dark daisies only. Both in Daisyworld and in the forest, such an act could lead to premature death by overheating, especially if it took place at a time or place where the Sun was hot. Geophysiologists and ecologists are agreed that the complex systems could not easily recover from insults like these; where we differ is over the stability of the monoculture, or the single daisy species. Geophysiology says that, because these ecosystems are limited in their ability to interact with the physical environment, they are unable to sustain their environment when exposed to a large perturbation. The humid tropics have remained forested, in spite of changes in the Earth's climate, which would be considered great in human terms but which are trivial on a planetary scale. The presence of great species diversity assists towards this robust capacity to withstand climatic change.

In most of the examples of Daisyworld, the Sun has been shown as steadily increasing its output of heat; an external perturbation that relentlessly increases in intensity until life can no longer continue. An alternative way of illustrating the stability of Daisyworld is to allow life to go on normally at a constant intensity of sunlight and then suddenly perturb the world by a change in climate or by some catastrophe such as a plague or planetesimal impact. Figure 3.5 shows a Daisyworld with 10 species of colored daisies whose stable existence is suddenly disturbed by a plague that kills 60 percent of the daisies, regardless of their color. In the lower panel, the dashed line represents the planetary temperature with no daisies present; at 40°C it is at the limit for life. The solid line illustrates the climate with daisies present before, during, and after the perturbation. The temperature stays in the mid-twenties, except when the plague first hits the daisy populations. When the perturbation is relaxed the system rapidly restores the status quo. The upper panel illustrates the variation in the distribution of species before, during, and after the catastrophe.

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Time (in arbitrary units)
3.5 The effect on climate of a plague that kills off 60 percent of the daisies on a Daisyworld when the solar luminosity is at a constant intensity. Note how homeostasis is restored in both population and temperature during and after the perturbation.


With this perturbation, the system is reluctant to move far from the comfortable state that existed before the change. The most marked effect of the disturbance is in the distribution of the different species of daisies. The rapid response of Daisyworld to change requires positive feedback and involves the explosive growth of those species whose interaction with the climate is the most favorable. This model has 10 species of daisies in a fixed, uniformly distributed range of colors from dark to light. An obvious extension of the research would be to include mutations and the possibility of evolutionary changes in the species. The abrupt change in the distribution of species at the perturbation event and again at its termination indicates the intensity of the selection pressure at these times. The experiment is much in accord with the observations of Stephen Jay Gould and Niles Eldredge on punctuated evolution. Instead of a steady, gradual change, as in the conventional Darwinian view, there are periods of abrupt and rapid evolution: the punctuation. Gaia theory would expect the evolution of the physical and chemical environment and of the species to proceed always together. There would be long periods of homeostasis with little environmental change or speciation, interrupted by sudden changes in both. These punctuations could be driven internally as a result of the evolution of some powerful species, like humans, whose presence alters the environment, or as the result of external change as from the impact of planetesimals.

The perturbation experiments and the steady-change experiments can be combined into one, as in figure 3.6. Here our world with 10 species of daisies is evolving as before, but now there is a recurrent plague affecting all colors equally. The plague strikes down 10 percent of the daisies, which are then allowed to recover only to become victims of a new form of the virus. And so the cycle continues throughout the evolution of the model. This experiment graphically illustrates the way that stability, as measured by the capacity to regulate the climate, correlates with diversity. The fluctuations of temperature are greatest at the birth and near the death of Daisyworld when the number of species is least. In the prime of its life, the effect of the perturbations is almost wholly resisted.

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Solar luminosity
3.6 The effect of a periodic plague of constant intensity on the ability of the daisies to control the climate. Note how the perturbation of the plague is amplified at the times of maximum stress near the beginning and the end of daisy life. The increasing amplitude of the oscillations in the latter part of the curve is reminiscent of the evolution of the present series of glacials and interglacials.


We shall come back to this experiment in chapter 6, in connection with the contemporary regulation of temperature by the biota through their capacity to affect the concentration of carbon dioxide in the air. This particular climate control system is nearing the end of its capacity to work and it can be argued that the recent oscillation of climate between ice ages and interglacials is like that near the end of Daisyworld in figure 3.6. The relatively minor perturbations of the Earth's orbital wobble that cause small variations in the amount of heat received from the Sun are amplified by the instability of a moribund system. These arguments do not necessarily apply to glaciations in the more remote past, which are likely to have had different causes.

The Daisyworld models that I have just described are complete but are expressed in ordinary English. Many scientists find such an expression of a theory unsatisfying and prefer the "rigor" of formal mathematical expression. For their benefit, the essence of the Daisyworld model is expressed in the simple diagram, figure 3.7, that my friend and colleague, Andrew Watson, devised. This model is based on a Daisyworld where there are only white daisies present. Because they are lighter in color than the soil in which they grow, they tend to increase the albedo of their locality, which, as a consequence, is cooler than a comparable area of bare ground. Where the daisies cover a substantial proportion of the planetary surface they will influence the mean surface temperature of the planet. The relationship between the area covered by white daisies and the mean surface temperature of the planet is illustrated as curve A. The parallel dashed line (A1) shows how the relationship might be shifted if there were a change in some external variable that influenced the planetary temperature -- for instance, if the star that warmed Daisyworld decreased its output of radiant heat.

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Temperature
3.7 Regulation by white daisies. The helmet-shaped curve (B) depicts the response of the daisies to temperature, and curves A and A1 are the response of planetary temperature to the area covered by daisies. Curve A1 is for a lower heat input from the star. In the absence of daisies, the change of planetary temperature (Delta-7) would be nearly 15°C whereas in their presence it is only about 3°C.


Like most plant life, daisies grow best over a restricted range of temperatures. The growth peaks near 20°C and falls to zero below 5°C and above 40°C. The relationship between planetary surface temperature and the steady-state population of daisies will be as in curve B, the curve shaped like a helmet. Curves A and B relate the planetary temperature to the population of Daisyworld at steady state; and the steady state of the whole system is specified by the point of intersection of these two curves. In the example, it can be seen that there are two possible steady-state solutions. It turns out that the stable solution is at the intersection where the rates of change of population with temperature are in opposite directions. In mathematical terms, where the derivatives of the two curves have opposite signs. The other intersection does not give a stable solution. If Daisyworld is started at some arbitrary but tolerable temperature it will move to the upper intersection point and settle there.

What happens to this stable state when some change takes place in the external environment? Suppose, for example, that the star warms up as our Sun is said to be doing. If the daisy population were artificially held constant, the planetary temperature will simply follow the change of heat output of the star; there will be a much larger change of temperature than if the daisies were allowed to grow to their new natural steady state, where they would oppose the effect of a change of stellar output.

Very few assumptions are made in this model. It is not necessary to invoke foresight or planning by the daisies. It is merely assumed that the growth of daisies can affect planetary temperature, and vice versa. Note that the mechanism works equally well whatever the direction of the effects. Black daisies would have done as well. All that is required is that the albedo when the daisies are present be different from that of the bare ground. The assumption that the growth of daisies is restricted to a narrow range of temperatures is crucial to the working of the mechanism, but all mainstream life is observed to be limited within this same narrow range. The peaked growth curve (B) is common to other variables besides temperature, for example pH (it can be too acid or too alkaline: neutrality is preferred). Similar restrictions apply to most nutrients; too much is poisonous, too little causes starvation.

The choice of a parabolic relationship for the response of daisy growth to temperature is arbitrary, and some people suggested that in real life the relationship takes on different or more complex forms. To test this objection, the Daisyworld model was run with different relationships between growth and temperature. These all retained the 5 to 40°C limit but ranged in shape from rectangular (a constant growth at all temperatures) to triangular (a linear increase up to a maximum, and then a linear decrease back again). Semicircular and rhombic relationships were also tried. The only limitation observed was that the models became unstable when a horizontal section was present in the relationship. Look back at figure 3.7 and imagine the helmet-shaped curve is replaced by one shaped as a top hat. The horizontal section, the top of the hat, would imply constant growth at any temperature within the 5 to 40°C range; consequently no regulation of temperature could take place. Such models are very similar to the simple competitive models of population biology where the environment is ignored and which are notoriously unstable. So long as the rate of growth of daisies varies with their temperature up to a maximum and then declines, even the gentle curvature of the top of a semicircle provides a working model.

In Nature, the shape of the relationship linking growth with some environmental variable frequently comes from the combination of a logarithmic rise overtaken by a logarithmic decay. In chapters 5 and 6 this relationship forms part of the model for the regulation of atmospheric oxygen. As oxygen increases in abundance the growth of consumers increases, but oxygen in excess is poisonous. Too little oxygen and too much both are bad; there is a desirable sufficiency.

Daisyworld differs profoundly from previous attempts to model the species or the Earth. It is a model more like those of control theory, or cybernetics, as it is otherwise called. Such models are concerned with self-regulating systems; engineers and physiologists use them to design automatic pilots for aircraft or to understand the regulation of breathing in animals, and they know that the parts of the system must be closely coupled if it is to work. In their parlance, Daisyworld is a closed-loop model. Devices that are not self-regulating are often unstable. Engineers refer to them as "open-loop"; the loops are the feedback links between the parts of the system. Daisyworld is not identical in form to an engineered device; a key difference is the absence, in Daisyworld, and perhaps in Gaia also, of "set points." In manufactured systems, the user sets the temperature, the speed, the pressure, or any other variable. The value chosen is the set point, and the goal of the system is to keep that value, however the external environment changes. Daisyworld does not have any clearly established goal like a set point; it just settles down, like a cat, to a comfortable position and resists attempts to dislodge it.

Because of the tribalism that isolates the denizens of the scientific disciplines, biologists who made models of the competitive growth of species chose to ignore the physical and chemical environment. Geochemists who made models of the cycles of the elements, and geophysicists who modeled the climate, chose to ignore the dynamic interactions of the species. As a result, their models, no matter how detailed, are incomplete. It is as if, in figure 3.7, the biology of the relationship between daisy population and temperature was considered without reference to the complementary geophysics of the relationship between temperature and daisy population. An engineer or physiologist would instantly recognize that such an approach was "open-loop," and consequently of little value except as an example of an extreme or pathological condition. There is also something pathological about the hubris of those scientists who boast of their special knowledge and of their disdain for that of other scientific disciplines. Sixty years ago that wise and generous-minded American theoretical biologist, Alfred Lotka, described the model of the competition of rabbits and foxes in The Elements of Physical Biology. It has been the inspiration of countless researchers in population biology ever since, yet none can have heeded his warning on page 16:

This fact deserves emphasis. It is customary to discuss the "evolution of a species of organisms." As we proceed we shall see many reasons why we should constantly take in view the evolution, as a whole, of the system (organism plus environment). It may appear at first sight as if this should prove a more complicated problem than the consideration of a part only of the system. But it will become apparent, as we proceed, that the physical laws governing evolution in all probability take on a simpler form when referred to the system as a whole than to any part thereof.


For three generations since, theoretical ecologists have modeled the evolution of ecosystems while ignoring the physical environment; and three generations of biogeochemists have modeled the cycles of the elements without ever including the organisms as part of a dynamic and responsive system. In Alfred Lotka's time the resolution of systems of nonlinear differential equations, even for a simple model like Daisyworld, was a daunting task. With the ready availability of computers there is now no need to continue with models constrained by the narrow limits of a single scientific discipline.

Lotka's insight, that modeling would be simpler with the whole system than with any part of it, is amply confirmed by modern mathematics. Systems of equations of the type describing model systems in theoretical ecology and biogeochemistry are notorious for their chaotic behavior, so much so that they now seem more interesting as playthings, or a new form of graphic illustration. The mathematics of natural phenomena, when constrained within a single discipline, can become so intricate and complex that world after world of colorful abstraction opens at every new level investigated. It is small wonder that practitioners of the various disciplines imagine that in these imaginary worlds they see glimpses of real world whereas in fact they are lost in the fractal dimensional world of a Mandelbrot set that goes on forever at every level from minus to plus infinity. The delusion is encouraged by professional mathematicians who find similarities between their mathematical theories and the pathologies of the real world, and the numerous modern mathematical scientists whose contemplation of the demons of hyper-space -- the "strange attractors" of chaos -- is much more beguiling than the dull old real world of Nature.

Daisyworld provides a plausible explanation of how Gaia works and why foresight and planning are not required for planetary regulation. But what evidence is there of practical mechanisms? What predictions from Gaia theory have been confirmed? Is it testable? The first test was the Viking mission to Mars. That expedition confirmed the prediction, from atmospheric analyses by infrared astronomy, that Mars was lifeless. Michael Whitfield, Andrew Watson, and I predicted that the long-term regulation of carbon dioxide and climate is by the biological control of rock weathering. These and other tests are described in the three chapters that follow. It matters little whether Gaia theory is right or wrong; already it is providing a new and more productive view of the Earth and the other planets. Gaia theory provokes a view of the Earth where

1. Life is a planetary-scale phenomenon. On this scale it is near immortal and has no need to reproduce.

2. There can be no partial occupation of a planet by living organisms. It would be as impermanent as half an animal. The presence of sufficient living organisms on a planet is needed for the regulation of the environment. Where there is incomplete occupation, the ineluctable forces of physical and chemical evolution would soon render it uninhabitable.

3. Our interpretation of Darwin's great vision is altered. Gaia draws attention to the fallibility of the concept of adaptation. It is no longer sufficient to say that "organisms better adapted than others are more likely to leave offspring." It is necessary to add that the growth of an organism affects its physical and chemical environment; the evolution of the species and the evolution of the rocks, therefore, are tightly coupled as a single, indivisible process.

4. Theoretical ecology is enlarged. By taking the species and their physical environment together as a single system, we can, for the first time, build ecological models that are mathematically stable and yet include large numbers of competing species. In these models increased diversity among the species leads to better regulation.

We have at last a reason for our instinctive anger over the heedless deletion of species; an answer to those who say it is mere sentimentality. No longer do we have to justify the preservation of the rich variety of species in natural ecosystems, like those of the humid tropical forests, on the feeble humanist grounds that they might, for example, carry plants with drugs that could cure human disease. Gaia theory makes us wonder if they offer much more than this. Through their capacity to evaporate vast volumes of water vapor through the surface of their leaves, trees serve to keep the ecosystems of the humid tropics and the planet cool by providing a sunshade of white reflecting clouds. Their replacement by cropland could precipitate a regional disaster with global consequences.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:30 pm

Part 1 of 2

4: The Archean

In the beginning there was nothing, not even space or time.

-- John Gribbin, Genesis


Life began a long time ago. The date of the event is not known, but it was at least three thousand six hundred million years before we were born. Numbers as large as this are anesthetic and paralyze the imagination. A different scale of reckoning time is needed to reach back to those bacteria, our ultimate grandparents. In science, the usual way of taming outrageous numbers is to express them as powers of ten. Make every step ten times larger or smaller than the one before. In his book Timescale: An Atlas of the Fourth Dimension, Nigel Calder illustrates the Earth's history in this way. He reminds us how easily this logarithmic sense of time can prevent us from recognizing how long life has occupied the Earth; to say that life began 3.6 x 109 years ago does not help. On a linear scale of measure, the origin of life was about a thousand times more remote than the origin of humans. In this book, I shall use a scale of eons, which represent a thousand million years. Life started at least 3.6 eons ago, during the period geologists call the Archean, the period that runs from the Earth's assembly 4.5 eons ago to 2.5 eons ago when oxygen first dominated the chemistry of the atmosphere.

Gaia is as old as life; indeed, if the Big Bang that started the Universe was 15 eons back from now, she is a quarter as old as time itself. She is so old that her birth was in the region of time where ignorance is an ocean and the territory of knowledge is limited to small islands, whose possession gives a spurious sense of certainty. In this chapter I invite you to join with me in speculating about the infant Gaia and the problems she faced in taking on her inheritance, the Earth. When we look at the Archean period in the light of Gaia theory, we see a planet radically different from that depicted by the conventional wisdom of present-day science. It is a planet where life does not just adapt to the Earth it finds itself upon, but also adapts the Earth to make it and keep it a home.

The best way to illustrate the powerful presence of Gaia is to consider what the Earth would be like without life. It will be argued that the present-day Earth could be an arid place like Mars or Venus had life not appeared upon it. We cannot make such a comparison for the Archean because we know so little about the Earth then. What we must do, therefore, is make a best guess about the condition of the Earth before life, and then consider the changes there would be when life took charge. By asking what the Earth was like before life began, we are in a way hanging up a neutral back cloth before which can be clearly seen the colorful changes made by life.

The trouble with doing this is that the back cloth is so old as to have all but moldered away. Looking back in time is like using a telescope to view the limits of the Universe. We can see faintly luminous objects. Astronomers make a convincing case that the distance of these objects is so great that the light now seen started its journey to the Earth 3.8 eons ago. This is close to the time geologists believe the first bacterial cells came into existence. They are probably correct, but the only certainty about such remote times and places comes from the great second law of thermodynamics. Enigmatically, it states that the beginning and the end of the Universe are unknowable. As time and distance lengthen, the once fair face of knowledge grows pockmarked with craters of ignorance. In the end, the features can no longer be recognized.

Information theory teaches that, in the presence of a constant amount of noise, the power required to send a signal across a gulf of space and time increases exponentially with the distance to be traveled. In simpler words: as the distance or the time lengthens, vastly more power is needed to transmit the same message. The happenings on Earth a mere 5000 years ago are far from known with certainty. Just imagine how large a signal would be needed to transmit information about the beginning of the Universe 15 eons ago. This may be why the Big Bang theory that the Universe began by the explosion of a primeval particle is inevitable. Nothing short of the explosion of the Universe itself could send a signal from so long ago. All that now lingers is the faint rumble of the cosmic microwave background radiation. But all other theories of the origin are without evidence.

There is a clever way to gather information about events as ancient as the start of life that avoids the otherwise universal tendency of messages to age and die. It comes from the nearly miraculous property of living matter to overcome the attenuating tendency of time. Not only has Gaia stayed alive from the beginning; she has also provided a noise-free channel of chemical messages about those ancient times.

If you stand on a hilltop and shout, you will not be heard more than a mile away. If you use a loud-speaker, you might be able to send a message 5 miles. Even exploding an H-bomb would make your point only for a few hundred miles. The alternative is to tell a friend who will take the message and pass it on by word of mouth. By this means, the message could travel without difficulty to the ends of the Earth. In a similar way, living organisms pass on the programs of the cell from one generation to the next. There is every reason to believe that we share with the first ancient bacteria a common chemistry, and that the natural restrictions on the existence of those ancient bacteria tells us what the environment of the early Earth was like. By transmitting coded messages in the genetic material of living cells, life acts as a repeater, with each generation restoring and renewing the message of the specifications of the chemistry of the early Earth. It is a much better channel of information than the record of the rocks. It is precise, but unfortunately it is inaccurate in the way that a message passed by word of mouth is precise and makes sense, but inevitably "mutates." There is the wartime joke that hides a truth: how the message passed by word of mouth, "Send reinforcements, we are going to advance" mutated into "Send three and four pence, we are going to a dance." If we wish to know life's origins from genetic information we need to be prepared to reconstruct the truth from errors of this kind.

By contrast, most of the geological information about the early Earth came from another big bang. It had to be large to send a signal so far. It was the explosion of a star-sized nuclear bomb, a supernova. We tend to ignore that we oddities, who use combustion as a source of energy, inhabit a nuclear-powered Universe. The power plants, the stars, run for billions of years with utmost reliability. But just as the most dependable systems we design can still have the occasional accident, so some kinds of stars occasionally explode. Fortunately for us, one of them did and gave us the start we needed. Fortunately, also, our Sun is not of the exploding kind; it is neither big enough nor old enough.

How can we be so sure that the Earth's origin was connected with the explosion of a supernova? We are sure because, even today, the Earth is radioactive, and also because the Earth is made of elements like iron and silicon and oxygen that cannot be made in the normal processes of stellar evolution. In the Sun and similar stars, hydrogen is fused to generate helium, and the reaction liberates the vast outpouring of heat that keeps us warm even 100 million miles away. But no ordinary fusion process can make elements such as iron, nor those such as uranium, which are heavier. It takes energy to make such elements. Powering a star by fusing iron to make uranium is like trying to burn ice in a furnace. This is not the place for fine details of element synthesis in exploding stars, except to say that in one kind of explosion the key part of the event is the gravitational collapse of the star. The innermost regions support the fantastic pressure of all the mass of the star trying to fall in. In their active life, the heat generated by nuclear reactions at the center of the star sustains a pressure high enough to balance the inward force of gravitation. It is just like a space rocket at the moment of takeoff; the weight of the vehicle is supported by the blast of flame. But the outer layers of the star cannot escape the pull of gravitation and, when the fuel runs out, it collapses. It is then that the heavy elements are synthesized. Some proportion of them is violently ejected as the outer and still unburnt layers of the star explode.

We still do not know how the Solar System and the Earth came together as a result of that supernova; nor how its radioactive debris became so large a part of our planet. But radioactivity is a marvelously accurate clock, and has precisely ticked away the time since that explosion 4.55 eons ago. We are so used to thinking of radioactivity as artificial that we easily ignore the fact that we ourselves are naturally radioactive. Every minute, in each one of us, a few million potassium atoms undergo radioactive decay. The energy that powers these minuscule explosive atomic events has been locked up in potassium atoms ever since that stellar explosion long ago. The element potassium is radioactive but it is also essential for life. If it were removed and replaced by the very similar element, sodium, we should die instantly. Potassium, like uranium and thorium and radium, is a long-lived radioactive nuclear waste of the supernova bomb. When potassium atoms decay, they are transmuted to form atoms of calcium and of the noble gas argon. The one percent of argon that goes to make up the atmosphere has, over the course of the Earth's history, mostly come from potassium in this way. In the rocks, the radioactive elements uranium and thorium are present at several parts per million. Their rate of decay is so slow that most of what was originally present still remains, except for the uranium isotope 235U, nearly all of which has decayed. It is the heat generated by the decay of these radioactive elements that keeps the Earth's interior hot and drives the movements of the crust.

The evidence from the rocks suggests that life began between 0.6 and 1 eon after the Earth had come together as a recognizable planetary body. The evidence is a difference in the proportions of the atoms of the stable element carbon. Carbon atoms exist on Earth in three forms: the common form weighs 12 atomic units, but there is a proportion weighing 13 units and a small trace of radioactive carbon weighing 14 units. These different-weight atoms are called isotopes. The proportion of the 12 and 13 isotopes, in the carbon of rocks made in the absence of life, is recognizably different from the proportion in carbon from rocks that were once living matter; this is because the chemistry of living matter segregates the isotopes. By measuring the isotopic composition of ancient rocks it is possible to distinguish those that were made when life was present from those that formed before life began. The most certain pre-life rocks we have come not from the Earth but from the Moon or from meteorites. These are as old as 4.55 eons. The isotopic proportion of these dead-matter rocks is easily distinguished from those laid down on Earth 3.6 eons ago. The oldest sedimentary rocks on Earth so far found are 3.8 eons old, and they come from a place called Isua in Greenland. I recall the German geochemist Manfred Schidlowski describing these ancient rocks in a 1973 lecture, and speculating that the carbon atoms within them when they formed showed an isotopic distribution suggestive of the presence of life.

The period before life has left no rocks from which we could reconstruct the details of the environment in which they formed; 4 eons or more of weathering and grinding has erased the record. It is likely to have been a time of unimaginable violence, with small planets left over from the condensation of the Solar System still crashing in. (The impact of a planetesimal a mere 6 miles in diameter can leave a crater 200 miles across, and splash molten rock and gas far out into space.) It left an Earth as cratered as the Moon. It was a period well named the Hadean.

The chemistry and physics of the period just before life began can only be surmised, and it will be interesting to watch as speculations blossom about the amazing and turbulent history of the Earth's beginnings. You can see, however, the difficulty in weaving the neutral back cloth referred to earlier. Therefore we will have to make the best we can of the information available, starting with the atmosphere.

The atmosphere is the face of the planet, and it tells, just as do our faces, its state of health and even if it is alive or dead. As we saw in chapter 1, planetary life is obliged to use any mobile media -- that is, the air or the oceans -- as conveyors of raw materials and as conduits for waste products. Such a use of these fluid media leads to profound changes in their chemical composition and to their departure from the near-equilibrium steady state characteristic of a nonliving planet. Dian Hitchcock and I used the absence of such changes in the atmosphere of Mars and Venus as evidence for the absence of life long before the Viking and Venera landers looked for and failed to find it. These dead planets are visually as well as chemically a neutral background against which the living planet Earth shines like a dappled sapphire.

There are many reasons why the atmosphere is so much more revealing about life than are the ocean or the crustal rocks. It is the region of rapid chemical change under the influence of sunlight; no mixture of gases capable of chemical reaction can long remain unchanged in the atmosphere. If we find a combustible gas like methane present with oxygen in a sunlit atmosphere, we know for certain that something is constantly making them both. No such conclusion could be drawn about air in a sealed underground cave. It is the sunlight that constantly keeps ignited all possible chemical combustions. Then the atmosphere has the smallest mass of all the compartments that life encounters; apart from the small concentration of rare gases like argon and helium, all other gases of the air have recently existed as part of the solids and liquids of living cells. The atmosphere also has an immediate effect on the climate and chemical state of the Earth, features of fundamental importance to life. A similar exchange takes place between life and the oceans and the rocks, but it is much slower in pace and the cycles of life are diluted by materials used long ago but now discarded.

The Earth, just before it became the habitat of life, then, must have been a dead planet whose atmosphere was near to equilibrium. At this time just before life, before Gaia, the atmosphere would have been in what scientists call the "abiological steady state." This wordy phrase is to distinguish the real planet -- which has hurricanes and tornadoes, volcanoes and whirlpools -- from the fiction of the utter stillness of an equilibrium planet.

The early Earth is thought to have had on its surface the chemical components from which life assembled, chemical compounds that are called "organic" -- such as amino acids, the subunits of protein; nucleosides, the subunits of the molecules of our cells that carry their genetic information; sugars, the subunits of polysaccharides; and many other essential parts waiting for the final act of assembly. It is important to recognize that these chemicals, although we regard them as characteristic of life, are also the products of the abiological steady state. The mere presence of such compounds on an oxygen-free planet is not by itself evidence for life. It is evidence only of the possibility of its formation.

Not only was the Earth's chemistry just right for life to start, the climate also must have been favorable. Some ancient rocks show evidence of having been formed by the sedimentation of particles. Their layered structure suggests an origin in a shallow lake or sea and, therefore, of the presence of free water. The existence of life and pre-life chemicals requires a temperature range between 0 and 50°C. The Earth could not have been frozen, nor could it have been hot enough for the seas to boil.

In an important paper in 1979, three atmospheric chemists and climatologists, T. Owen, R. D. Cess, and V. Ramanathan, reported calculations to determine the average temperature of the Earth at the time life began. They used the general consensus of astrophysicists, that stars grow hotter as they age, and supposed that the output of heat from the Sun was 25 percent less than it is now. They took values for the approximate amount of carbon dioxide gas that had escaped (or outgassed) from the Earth's interior. From this, they were able to calculate that the mean surface temperature of the Earth was 23°C; typical of the tropics today. Their calculations required the presence of 200 to 1000 times as much carbon dioxide in the air as there is now. Much would depend on the quantity of nitrogen present. If then, as now, nitrogen was the principal atmospheric gas, then the lower pressure of carbon dioxide would have sufficed. Also important, according to my friend the climatologist Ann Henderson-Sellers, would have been the distribution of water as oceans, snow, ice, clouds, and water vapor. Not surprisingly there is still debate about the climate on the occasion of life's start. Calculations by the climatologist R. J. Dickinson in 1987 suggest it may have been a few degrees cooler, in other words just about the same as now.

The idea was that the lack of warmth of a cooler Sun could have been offset by a blanket of "greenhouse" gas. Gases with more than two atoms in their molecules have the interesting property of absorbing the radiant warmth, the infrared radiation, that escapes from the Earth's surface. These gases, which include carbon dioxide, water vapor, and ammonia, are transparent to the visible and the almost visible infrared radiation. These are the parts of the Sun's spectrum that carry most of its energy; radiant heat in this form will penetrate the air and warm the surface. The same gases are opaque to the longer wavelength infrared that radiates from the Earth's surface and lower atmosphere. The trapping of the warmth, which otherwise would escape to space, is the "greenhouse effect"; so called because it is like, although not the same as, the warming effect of the glass panes of a greenhouse. The first proposal that a gaseous greenhouse warmed the Earth was made by a distinguished Swedish chemist, Svante Arrhenius, in the last century.

H. D. Holland, in The Chemical Evolution of the Atmosphere and the Oceans, gives a clear and readable statement of the probable state of the Earth just before Gaia awoke. In summary, he proposes an Earth with an atmosphere rich in carbon dioxide, with nitrogen present but bereft of oxygen, and with traces of gases such as hydrogen sulfide and hydrogen present. The oceans were laden with iron and other elements and compounds that can only exist in solution in the absence of oxygen. Among these could have been reduced compounds of sulfur and nitrogen. The presence of these gases and substances is important, because they are reducing agents -- they readily react with, and so remove, oxygen. Such an Earth would have a vast capacity to absorb oxygen and prevent its appearance in the free state. This proposal seems so reasonable that I shall take it as if it were a fact and use it as a key to understanding the evolution of the Archean period of the Earth's history.

One other condition of the nascent Gaia is that three times as much internal heat was produced as now. This was because the Earth was more radioactive; less time had elapsed since the supernova that made it, and the fallout was still hot. It would be wrong, though, to think that this internal heat had an appreciable effect on the surface temperature of the Earth. The heat flux from below was trivial compared with that received from the Sun. The principal effect of greater production of internal heat would have been more vigorous volcanism, a higher output of gas to the air, and a more rapid reaction of volcanic rocks with the ocean waters. One of these reactions, that between the ferrous iron of basalt rock and water, can produce hydrogen gas. The continuous production of hydrogen would have had two important consequences. First, the maintenance of an oxygen-free atmosphere and surface favorable for life chemicals to accumulate. Second, the loss of hydrogen to space. The Earth's gravitational field is not strong enough to hold down the light atoms of hydrogen. If hydrogen escape had continued, we might have lost much of the oceans or even arrived at the arid state of Mars and Venus. (Such an escape cannot take place now because hydrogen would react biochemically in the oceans and with the abundant oxygen in the atmosphere to form water. Although it carries two hydrogen atoms, water is too heavy a molecule to escape directly into space. Another restraint on the direct loss of water from Earth is its tendency to freeze out and fall back as ice crystals from frigid regions of the air.)

That, then, was the Earth before life. We can accept as reasonable the view that life started from the molecular chemical equivalent of eddies and whirlpools. The power that drove them was the flux of energy from the Sun and also the free energy of a hot young Earth. Prigogine and Eigen have plausibly formulated the physical mechanisms by which chemicals and cyclical reactions come together as dissipative structures of protolife. The stepwise evolution from protolife to the first living cell by a process of natural selection does not seem to me so difficult an intellectual pill to swallow. It would be interesting to know if protolife was tightly coupled to its environment and had the capacity to regulate. Two geochemists, A. G. Cairns-Smith and Leila Coyne, have alternatively suggested that the solids of the environment played a crucial part in life's origin. To my mind their ideas help to crystallize the supersaturated arguments, even though their details are disputed. The problem with dissipative structures of the fluid state is that they dissipate too soon. If they are to evolve to more permanent structures, something solid is needed to serve as an anchor or to house them. Again, the mental image of a wind instrument like a flute is helpful in this otherwise confusing topic. Just blowing makes a hiss of unruly dissipating eddies. But when the flutist blows across the port hole of the flute, the eddies are caught and tamed within the solid bounds of its hollow resonant tube to emerge as coherent musical notes. In their evolution, living organisms, too, seem to have used the security of the solid state of matter to store and pass on to their descendants the message of existence. The special solid state of the aperiodic crystals of DNA store the programs of the cell, and give organisms a span far beyond that of a dissipating eddy or a chemical cycle.

The first living cells may have used as food the abundant organic chemicals lying around; also the dead bodies of the less successful competitors and the bodies of the successful ones that died of natural causes. These supplies of raw material and energy may soon have become scarce, and at some early time organisms discovered how to tap the abundant and inexhaustible energy of sunlight to make their own food. It is thought that the first of the photosynthesizers used the less demanding photochemical dissociation of hydrogen sulfide. Soon the real prize, how to use light energy to break the strong bonds binding oxygen to hydrogen and carbon, was won. Bacteria now called cyanobacteria, because of their blue-green color, did just this and are the predecessors of all green plants that now exist.

There was a complete planetary system in the Archean. At the surface -- in the sunlight -- there were the primary producers, cyanobacteria (ancestors of those shown in figure 4.1), that used solar energy to make organic compounds and replicate themselves. They also would have made oxygen, but the abundance of reactive inorganic chemicals in their environment would have kept this gas close to the site of its production. Also present in the early ecosystem were the methanogens that gained material and some energy by rearranging the molecular products of the producers. The presence of these "scavenger" organisms would have assured the continuous disposal of the products and corpses of the photosynthesizers and the return to the environment of the essential element carbon as methane and carbon dioxide. They could not, as we and animals do, eat the cyanobacteria and use the food they had synthesized; to do this they would have needed oxygen.

I suspect that the origin of Gaia was separate from the origin of life. Gaia did not awaken until bacteria had already colonized most of the planet. Once awake, planetary life would assiduously and incessantly resist changes that might be adverse and act so to keep the planet fit for life. Sparse life hanging on in oases could never have the power to regulate or oppose the unfavorable changes that are inevitable on a lifeless planet. Sparse life would only be found at the birth or death of a Gaian system.

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4.1 Photomicrographs of cyanobacteria. These are the organisms that first used the energy of sunlight to produce organic materials and oxygen. They have been, both in the free state, and as endosymbionts, the primary producers from the beginning of the Archean until now. (Photographs courtesy of Michael Enzien.)

The successful evolution of the photosynthesizers could have led to the first environmental crisis on Earth, and I like to think the first evidence of Gaia's awakening. In gaining their energy, the photosynthesizers would have used the carbon dioxide of the air and the oceans as their source of carbon. Just as we have a carbon dioxide problem now, so might they. We are beginning to realize that the benefits of burning fossil fuel as a source of energy are offset by the dangers inherent in the accumulation of carbon dioxide; it could lead to overheating. The danger faced by the photosynthesizers was the reverse. The cyanobacteria used the carbon dioxide as food. They were eating the blanket that kept the Earth warm. There was at that time a vigorous input of carbon dioxide from volcanoes, but the potential capacity of the bacterial sink could have far exceeded this source. If there had been only photosynthesizers, their abundant bloom over the oceans and on the surface could have reduced the carbon dioxide in a few million years to dangerously low levels. Long before the cyanobacteria ran out of carbon dioxide to eat, the Earth would have cooled to a frozen state and life could have persisted only where heat from below could melt the ice, or moved into a cycle of freezing and thawing as carbon dioxide from volcanoes accumulated and was then removed again. I think that neither of these calamities ever happened. The persistent presence of sedimentary rocks from 3.8 eons ago until now suggests that liquid water has always been present and the Earth has never been entirely frozen. What I would like to propose is a dynamic interaction between the early photosynthesizers, the organisms that processed their products, and the planetary environment. From this there evolved a stable self-regulating system, a system that kept the Earth's temperature constant and comfortable for life.

Before venturing further into this imaginary reconstruction of life with Gaia in the Archean, I must emphasize that it will be no more than a flight of fancy. Solid evidence from the early Archean is scarce, and many different models can be made of it. The eminent geologist, Robert Garrels, often reminds me that in his model of the early Earth, the carbon dioxide remained abundant (about 20 percent by volume) and the Earth was hot (40°C or higher). The point of my model is not to argue for one or other global Archean ecosystem, but rather to illustrate how Gaia theory provides a different set of rules for planet models. The possible climatologies and geologies of a living planet are wholly different from those of a dead planet bearing life as a mere passenger. Having said this, let us continue with our "let's pretend."

In the Archean, photosynthesizers used carbon dioxide and converted it to organic matter and oxygen or its equivalent; just as plants do today. The oxygen would have been mopped up immediately by the ubiquitous oxidizable matter of the environment; the iron and sulfur in the oceans. There was no significant population of oxidizing consumers grazing the photosynthesizers and returning carbon to the environment as carbon dioxide. There was, except in juxtaposition with the producers, no oxygen for consumers to breathe. Instead, there were the methanogens, scavengers and descendants of the original decomposers of organic chemicals. These early bacteria, capable of existence only in the absence of oxygen, lived by decomposing organic matter and converting the carbon in it to carbon dioxide and methane which they return to the air. They served in the Archean, like the consumers of today, to return to the air almost as much carbon as had been removed by the photosynthesizers.

But what of the methane? Methane is a greenhouse gas like carbon dioxide, but it is much less stable in the atmosphere; it decomposes in solar ultraviolet light and reacts with hydroxyl radicals -- small molecules, with one atom each of hydrogen and oxygen, that are amazingly reactive and scavenge from the air all but the most stable molecules. It is reasonable to suppose that, in the Archean, this photochemical reaction zone would have been high in the atmosphere but at a level where the air was still dense enough to absorb ultraviolet. When ultraviolet breaks down methane, the products combine and recombine with other molecules to form a suite of complex organic chemicals. Suspended high in the stratosphere, these products could include droplets and particles; an upper-atmospheric smog. Such a layer could have profoundly changed the Archean environment. In its presence, the ultraviolet and visible radiation from the Sun would have been absorbed, and the region where the absorption occurred would have grown warmer. The presence of this warm layer in the atmosphere placed an "inversion" lid on the lower atmosphere, and would have reversed the normal tendency for a fall in temperature as one ascends from the surface. In other words, methane smog would have been the Archean equivalent of the ozone layer and would have acted, just as ozone does, both to stabilize the existence of the stratosphere and to filter out ultraviolet radiation.

The existence of a lid, the "tropopause," above the lower atmosphere would have reduced the flux of methane to the regions where it was destroyed by ultraviolet; just as the foul air is trapped beneath the inversion layer of this century's air-pollution smogs. By this means, the methane concentration could have built up sufficiently to be useful as a greenhouse gas; also, its reaction products in the stratosphere, including water vapor, would have served in the same way. The screening out of ultra-violet by the smog layer would have protected other unstable gases such as ammonia and hydrogen sulfide and allowed them to accumulate to some extent in the lower atmosphere. Ultraviolet normally decomposes hydrogen sulfide and other similar gases, both directly and by other photochemical reactions that produce the hydroxyl radicals. It is conceivable that the lower atmosphere, shielded by the methane smog, contained some free oxygen coexisting with an excess of methane; just as there is free methane in small quantities coexisting in an excess of oxygen in the air we breathe now. This would be even more probable if the photosynthesizers existed in self-contained communities at the surface. Some of the oxygen they made would then diffuse into the air and persist for much longer than that released into the oxygen-hungry waters of the oceans. In a fully detailed model, we ought to include gases such as nitrous oxide, carbonyl sulfide, and methyl chloride; all are components of our present atmosphere. For this model, it is enough to bear in mind this possibility and the amazing and intricate series of reactions and consequences that could come from their presence.

How stable would a planetary ecosystem be that was made up from photosynthesizers using carbon dioxide and decomposers that converted organic matter back to carbon dioxide and methane? In many ways the photosynthesizers are like white daisies; their growth cools the Earth by removing carbon dioxide. The methanogen decomposers are like dark daisies; their growth makes for warmth by adding greenhouse gases to the air. It is not difficult to model the simple world I have just described, constructed just as were the daisy models of chapters 2 and 3. Figure 4.2 illustrates the time course of the evolution of the Earth's average temperature, the atmospheric gases, and of the population of the bacterial ecosystem. The model used H. D. Holland's estimate of the input of carbon dioxide from volcanoes, but the sink for carbon dioxide, by the weathering of rocks, was assumed to increase as the ecosystem developed. I based the climate regulation mainly on the capacity of carbon dioxide and methane to act as greenhouse gases. A small additional effect was assumed to occur -- the colonization of the land surfaces would increase cloudiness and tend to increase the back reflection of sunlight.

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Time (eons before present)
4.2 Model of the Archean before and after life. The upper panel shows the climate with and without life and the lower panel the abundance of the atmospheric gases and bacterial population as the system evolved. The scale for the abundance of atmospheric gases is logarithmic; the scale for population is in arbitrary units.


The upper part of figure 4.2 illustrates the time history of the temperature of this anoxic world with and without the presence of life. The dashed line is the expected temperature rise of a lifeless planet that has enough carbon dioxide to make up an atmospheric pressure of 100 millibars; about one-tenth of the present total atmospheric pressure. The bulk of the atmosphere was assumed to be nitrogen as it is now on Earth. The star was assumed to be 25 to 30 percent less luminous than the Sun is now, but to warm up as time passed in the same way as did the Sun. The solid line marks the temperature of the model world where photosynthesizers are coexisting with methanogens. Note the abrupt and sudden fall in temperature from around 28°C to 15°C after life starts. This is due to rapid decline in the abundance of the greenhouse gas, carbon dioxide, as the photosynthesizers use it to build their bodies. The fall does not continue until the planet freezes because the new greenhouse gas, methane, and some carbon dioxide are returned to the air by the methanogens. Once a steady state is established, throughout the Archean. The sudden fall in temperature at about 2.3 eons ago marks the end of the Archean in the model and the appearance of an excess of free oxygen in the air. This event would have led to a decline of methane gas to near its contemporary abundance, thereby removing its greenhouse effect. The model matches the Earth's ancient history. There is no evidence of unusual temperature change during the Archean, and there was a cold glacial period 2.3 eons ago that may have coincided with the appearance of atmospheric oxygen. The lower part of figure 4.2 shows how the total population of bacteria the model evolved. The start of life is seen to coincide with the fall of carbon dioxide and the rise of methane. The end of the Archean is marked by the disappearance of methane.
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Re: THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH by Ja

Postby admin » Fri Oct 09, 2015 8:30 pm

Part 2 of 2

This simple model, like Daisyworld, is robust and is not easily disturbed by changes in solar input, bacterial population, or the input of carbon dioxide from volcanic sources. It is sensitive to changes in the range or form of the relationship between the growth of the bacteria and the temperature of their environment. The model is based on the assumption that growth of the bacterial ecosystem ceased at freezing point, was maximum at 25°C, and ceased again at temperatures above 50°C. Like Daisyworld, there is an abrupt change of conditions when life starts. Living organisms grow rapidly until a steady state is reached where growth and decay are in balance. This rapid, almost explosive, tendency to expand to fill an environmental niche acts as an amplifier. The system moves rapidly in positive feedback to approach a balance. Soon stability is achieved and the planet runs on in comfortable homeostasis.

The atmosphere of this new model of the Archean would be like a somewhat diluted version of the gas above a septic tank or a biogas generator -- smelly and toxic for us, but delightful for the denizens of those ancient times. The atmospheric abundance of both carbon dioxide and methane would range between 1.0 and 0.1 percent. It is interesting that H. D. Holland was doubtful about the continuation of an atmosphere with a high content of carbon dioxide for long into the Archean. The rates of rock weathering from the geological record are not consistent with the persistence of 10 percent or more carbon dioxide. The rapid removal of carbon dioxide by the bacterial ecosystems neatly removes this problem. It is worth noting that many kinds of bacteria, not just photosynthesizers, actively remove and use carbon dioxide and make chemical compounds from it.

Table 4.1 ESTIMATE OF THE ARCHEAN ATMOSPHERIC COMPOSITION BEFORE AND AFTER LIFE APPEARED

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According to the model, the atmosphere was wholly different in composition in the Archean after life began. Table 4.1 illustrates the mixing ratio of the principal atmospheric gases before and after life. It shows an increase in nitrogen abundance after life began: I speculated that, until then, some of the nitrogen was present as the ammonium ion (NH4)+ in the oceans. The sea was more acid from the excess of carbon dioxide, and was rich in ferrous iron. In these circumstances, the ferrous iron may well have sequestered a large proportion of the ammonium ion to make a stable iron-ammonia complex compound, in which form much of the element nitrogen would have existed. Both the fall in carbon dioxide and the use of nitrogen by life could have changed the balance in favor of nitrogen gas in the air. Although nitrogen has no greenhouse effect by itself, the increase in nitrogen would have doubled the atmospheric pressure and this would have increased the greenhouse effect of the carbon dioxide and methane gases. The reason for this is somewhat recondite, but is connected with an increase in the amount of infrared absorbed by the greenhouse gases when total atmospheric pressures are higher.

It is important to note that there are other equally plausible models of the Archean. The conventional wisdom is expressed in Holland's book; it sees the pre-life environment continuing unchanged. Robert Garrels prefers to see the period as one where there were high temperatures sustained by high concentrations of carbon dioxide in the air. It is likely to be a long time before we are certain about the ancient history of the Earth. The purpose of this chapter, however, is not to make a firm statement on conditions during the Archean; it is to show how Gaia theory can be used to build from the meager evidence a different picture of those times.

I like to imagine some alien chemist arriving in the Solar System long ago and viewing the Earth's pre-life atmosphere. The infrared spectrometer aboard the spacecraft would recognize a planet in the abiological steady state -- a planet not yet alive, but with the potential to bear life. On a second visit much later in the Archean, when life had taken charge, a similar analysis would show a degree of chemical disequilibrium impossible for a lifeless planet. Carbon dioxide, methane, hydrogen sulfide, and oxygen cannot coexist at the levels shown in table 4.1 in the presence of sunlight. Given the destructive effects of solar ultraviolet radiation on methane, oxygen, and hydrogen sulfide, the alien would know that there was a large, continuous source of these gases. No conceivable volcanic source could sustain such an atmosphere. The alien would conclude that the Earth was now alive.

I often wonder what the Archean Earth would have looked like to us. I suspect that from an orbiting spacecraft we would not have seen the familiar blue-and-white sphere with glimpses of land and sea beneath the aerial canopy. More likely, the view would have been of a brownish-red, hazy planet; like Venus or Titan, too obscured to see the surface below. The sky that now we see as blue and clear results from an abundance of oxygen. Oxygen is the permanent bleach that clears and freshens the air.

On a beach on the edge of an Archean continent, we would see waves breaking on smooth sand, and sloping dunes behind. It would be familiar except for the colors. The Sun high above would have an orange glow more like sunset. The sky would be a pinkish hue, and the sea, that great copyist, shades of brown. There would be neither shells nor tracks of moving things upon the sand. The breakers offshore would fall away at low tide, exposing reefs of the strange mushroom-shaped stromatolites formed by the calcium carbonate secreted by colonies of living cyanobacteria. Inland, behind the sand and shingle dunes, would be flat and stagnant water, with patches of matted green and black bacterial growth. Other than the wind and waves, the only sound would be the plop of methane bubbles bursting as they broke from containment in the mud. Beyond the lagoon and on the continental surface, the same scene would repeat wherever there were shallow depressions in which water could gather. On the drier land and on the hill sides, a thin varnish of microbial life would ceaselessly work at weathering the rocks, releasing nutrients and minerals into the flow of rain water, and continuously removing carbon dioxide from the air. This quiet landscape could have persisted throughout much of the Archean. But there would have been violent interruptions when planetesimals crashed in from space. There were at least ten of these collisions; each a catastrophe great enough to destroy more than half of all planetary life. They would have changed the physical and chemical environment enough to hazard the remainder of life for hundreds if not thousands of years to follow. It is a tribute to the strength of Gaia that our planetary home was restored so promptly and effectively after these events.

Without life, the scene would have been much different. The ineluctable forces of chemical and physical evolution drive the small inner planets to an oxidized state through the loss of hydrogen. Venus must have had some water in the beginning. Estimates from the abundance of the unreactive noble gases suggests that, when the planets formed, Venus may have had at least a third as much water as the Earth. Where did it go? It seems most probable that the reducing elements of iron and sulfur in the surface rocks sequestered the oxygen of the water molecules. These reactions set hydrogen free as a gas, the light atoms escaping into space. The solar ultraviolet at the edge of the atmosphere may also have split some water vapor into hydrogen and oxygen. Either way, hydrogen, and hence water, was lost forever and the planet made more oxidized. Venus now, with its furnace heat and brimstone-laden air, is a model for Hell. By comparison, the Earth is Heaven for the life it bears.

How have we kept our oceans? It seems likely that the presence of life has done it. Robert Garrels tells me that his calculations suggest that, but for life, the Earth could have dried out in about 1.5 eons, midway through the Archean. There are several ways of retaining hydrogen on a planet. One is to add oxygen to the atmosphere or environment so that it captures hydrogen to form water. Life, in the act of photosynthesis, splits carbon dioxide into carbon and oxygen. If some of the carbon is buried in the crustal rocks, there remains a net increment of oxygen. For every atom of carbon buried, two atoms of oxygen are left behind. Each atom of carbon buried, therefore, is in effect four atoms of hydrogen or two molecules of water saved. Then there are the reactions at the ocean floor between sea water and the ferrous iron in basalt rock. The free hydrogen that these produce would be food for the bacterial species who could gain energy by using it to make methane, hydrogen sulfide, and other compounds less volatile than hydrogen. Methane, decomposed in the atmosphere by ultraviolet, could stratify the atmosphere and slow the rate of mixing of gases from the lower atmosphere, which would also hinder the escape of hydrogen to space. In these and other, more subtle ways, the presence of life in the Archean saved our planet from a dusty death.

Elso Barghoorn and Stanley Tyler first discovered the fossil bacteria that led to the recognition of the presence and the form of life in Archean times. I once visited Barghoorn's laboratory at Harvard University, and saw for myself the exquisite technical skills he used to cut, with diamond saws, the thin transparent slices of flinty rock. In this way, he and Tyler found the microfossils of bacteria in the ancient Gunflint rocks of the Great Lakes region of North America. But all these ancient fossils are from wet places, and we still do not know if there was life on the dry land. I find it hard to believe that a life form as enterprising as bacteria would have left unused the land surfaces. At this point, I should like to tidy away what I believe to be a persistent false assumption about those early times. We are using a new theory to view the scene; it helps to have the few genuine pieces of evidence displayed on a clean sheet.

The false image, that lingers like a mirage, is the shibboleth, "Earth's fragile shield." In a way, the atmospheric scientists L. V. Berkner and L. C. Marshall started it. Some thirty years ago, they introduced their famous theory on the evolution of atmospheric oxygen. Crucial to this was the assumption that there was a flux of lethal ultraviolet radiation before oxygen was present in the air and that this prevented life from colonizing the land surfaces. Indeed, it was further held that life before oxygen must have been obliged to exist deep in the sea at levels where the ultraviolet could not penetrate. It was only after oxygen appeared in the air that ozone could form and act as a shield to prevent the ultraviolet from reaching the surface. Once this happened, the way was open for an abundance of life to colonize the land and for the growth of oxygen concentration by increased photosynthesis to its present level of 21 percent. Some details of their theory we now suspect are wrong, such as that oxygen was at times more abundant than it is now. But this is no discredit; the information needed to test their theories was not then available. We owe an immense debt to Berkner and Marshall for the stimulating effect their ideas had on the development of the Earth sciences. Like Vernadsky and Hutchinson before them, they were scientists who presented a world model in which life had a part to play and was not just a spectator obliged to adapt to the climatic and chemical whims of a purely physical and chemical world. The scientific establishment accepted their ideas enthusiastically. Among those ideas was the minor postulate that the presence of a stratospheric ozone layer is an essential requirement for surface life. Almost every scientist now accepts it as if it were a proven fact of science.

There could have been no ozone layer at the start of life and during the Archean; gases like hydrogen and methane were dominant in the atmospheric chemistry, and even if there had been some oxygen in the atmosphere it could not have been used to form ozone. (Ozone is produced when ultraviolet radiation in the stratosphere splits molecules of oxygen into two separate atoms, which then combine with other molecules of oxygen to form a three-atom variety of oxygen: O3.) The intensity of ultraviolet in the absence of ozone would have been 30 times higher than is now incident upon the Earth's surface. Such an irradiation, it is said, would have sterilized the land surfaces. The more committed believers in the potency of ultraviolet hold that 10 to 30 meters of ocean water are needed to filter out the deadly radiation. Life, they say, could not have existed in shallower depths of the sea, let alone on the surface.

Much more probably, "Earth's fragile shield" is a myth. The ozone layer certainly exists today, but it is a flight of fancy to believe that its presence is essential for life. My first job as a graduate was at the National Institute for Medical Research in London. My boss was the courteous and distinguished generalist, Robert Bourdillon. I was privileged to watch, and later participate in, the experiments that he and my colleague, Owen Lidwell, made as they tried to kill bacteria by exposing them to unfiltered ultraviolet radiation. Our practical objective was the prevention of cross infection in hospital wards and operating theatres. We were seeking a way to kill airborne bacteria and so prevent the spread of infection. Naked washed bacteria of some species, when suspended in the air as fine droplets, were easily destroyed by ultraviolet. It was impressive, though, how small a film of organic matter would almost entirely protect even these sensitive species. In the real world outside the laboratory, bacteria do not exist suspended in distilled water or a saline solution. In their normal habitats, bacteria are clothed in mucus secretions or the organic and mineral constituents of their environment. They do not live naked anymore than we do. Many practical trials were made before it was realised that ultraviolet radiation is not an effective method of eliminating from the hospital environment the tender fragile pathogens. It takes almost no clothing to stop ultraviolet radiation. [1]

The memory of these experiments left me disinclined to accept that the much weaker irradiation of the land surfaces in the Archean by natural ultraviolet could have prevented their colonization. The organisms then around were used to living outdoors in the sunlight and had millions of years in which to adapt themselves or the Earth. It is also wrong to assume that ozone alone among atmospheric gases can filter out ultraviolet light. Many other compounds absorb and remove shortwave ultraviolet radiation. The most probable candidates in the Archean would be the smog-like products from the decomposition of methane or hydrogen sulfide. In the ocean there are even more possibilities. The abundant ions of such transition elements as iron, manganese, and cobalt are intense absorbers of ultraviolet, as are the ions of nitrous acid and of many organic acids. But even if the full unfiltered solar ultraviolet shone on the surface, it still would not have much hindered life. Organisms are nothing if not opportunistic. They would probably have turned the hard ultraviolet light to use as a premium energy source. It is an insult to the versatility of biological systems to assume that a weakly penetrating radiation like solar ultraviolet could be an insurmountable obstacle to surface life. Even dark-skinned humans are almost immune to its effects; and it is used in the skin of us all for the opportunistic photobiochemical production of vitamin D.

This belief that ultraviolet radiation is unconditionally lethal to life on Earth has sustained a distorted view of the Archean and of other periods in the evolution of Gaia. And it is a view still deeply entrenched in scientific thinking. I found it to be common among the scientists who sought life on Mars. I could not help wondering how they could think that there was life on the intensely irradiated surface of Mars and at the same time believe that the land beneath the thick and murky Archean atmosphere of Earth was sterile. How could they fit into their minds two such contrary ideas?

I think that a more serious threat to the health of land colonies in those times would be the need for rain. Rainfall on the continental land masses of the present Earth is, to a considerable extent, a consequence of evapotranspiration: the pumping by trees and large plants of water from the soil to their leaves where it evaporates. The rising plumes of water vapor over forests act like invisible mountains and force the inflowing air from the oceans to rain out its burden of water. Even if bacterial life grew to form stromatolites, it is unlikely that these colonial structures that rose above the surface would be as efficient at rain making as trees. (Small though they are, however, bacteria do have tactics for rain making. Recently, scientists have found that bacteria of Pseudomonad type synthesize a macromolecule which can induce freezing in water droplets supercooled below O°C.)

Although bulk water, as in a swimming pool or even in a glass, freezes when its temperature falls below O°C, droplets of water that have condensed inside a cloud may not freeze until the temperature falls to -40°C. This supercooling takes place in the absence of nuclei of solid particles onto which the first microscopic ice crystal can form and grow. Pure water is reluctant to freeze; it freezes in our refrigerators because, in bulk water, there is always at least one nucleus to start the process of nucleation. Some chemical substances, such as silver iodide, have crystals close enough in shape to mimic ice. If these are dusted on a supercooled cloud, they will start the freezing process and sometimes the fall of rain. The macromolecule that the pseudomonads synthesize can cause droplets cooled only to -2°C to freeze, and is far more efficient than silver iodide. (This has led to commercial interest in methods of rain making. Silver iodide crystals work after a fashion, and production of the efficient pseudomonads macromolecule is under way. But it is thought by some environmentalists to be socially undesirable; the stealing of rain that might otherwise have fallen on those who may have needed it more.)

Pseudo monads have an ancient history, and maybe their ice-nucleation trick goes back to the Archean. If so, were they the rain makers that led the colonization of the land? A question that always arises at this point in speculation is: How did it happen? Surely the bacteria did not decide to make the ice-nucleating substance. At this point, serious-minded microbiologists grow anxious and fear the proximate occasion of teleological heresy. Fortunately, we can easily make a plausible model of the evolution of close coupling between a large-scale environmental effect and the local activity of microorganisms -- a model, moreover, free of any taint of purpose.

It is probable that the regional and global physiological systems of Gaia have their origins in some local competition and negotiation between species. An early variant of the ice maker may have found that the freezing of dew at its growth site gave some advantage. It might have been destroying a competitor or predator by freezing, splitting the tough skin of a food organism, or producing mechanical fractures in rocks to release nutrients or increase the quantity of soil particles. Any of these effects, alone or in combination, would confer advantage on the ice maker and, more important, favor those that made the most or the best nucleator. Eventually, the best possible nucleator would be ubiquitous in its distribution. For purely local reasons, these bacteria would continue their freezing activity wherever it was to their advantage. It is not difficult to see that surface ecosystems carrying ice makers would be at an advantage under drought conditions compared with those unable to produce the nucleating agent. The soil dust stirred by the wind or lifted by whirlwinds could induce droplet freezing in the clouds and then rainfall.

The connection between the freezing of cloud droplets and the subsequent fall of rain is well understood. A great amount of heat is released when water freezes; in other words, freezing half of the water in a drop supercooled to -40°C releases enough heat to raise the temperature of the mixture of water and ice by 40° to the freezing point. If a large proportion of supercooled droplets in a cloud freeze, the latent heat released warms the cloud and causes it to rise. More water vapor condenses and freezes so that ice and snow falling though the cloud gather water and weight, and fall as rain. Any product of living organisms that nucleates supercooled cloud droplets will therefore encourage rain.

More important in climate regulation than the nucleation of supercooled water droplets is the nucleation of supersaturated water vapor. The air above the open ocean is often supersaturated with water vapor. But no clouds or moist droplets can form until fine particles, the cloud condensation nuclei, appear. The climatologist Robert Charlson has argued that the emissions of sulfur compounds by the biota now and in the recent past has played an important role in providing cloud condensation nuclei. But this requires the presence of atmospheric oxygen to oxidize the sulfur to sulfuric and methanesulfonic acids, the nucleating agents. This could not have happened in the Archean, but there may have been other molecular species that served in this way. The aerosol of sea salt from breaking waves has some capacity to nucleate clouds, but it is slight compared with that of the sulfur acid micro-droplets.

Although rainfall is essential for growth on the land, it also poses problems because it washes away nutrients. (The poor productivity of the rain-washed uplands of the west coast of the British Isles is an example of this problem.) Today, rivers carry to the ocean elements that are used or required by marine life -- such as nitrogen, phosphorus, calcium, and silicon. But the rivers also carry the rarer elements -- sulfur, selenium, and iodine -- to the sea, and the land becomes depleted. This brings us to another large-scale geophysiological mechanism: the transfer of essential or nutritious elements from the ocean, where they are abundant, to the land, where they are scarce. The process requires marine life to synthesize specific chemical compounds that act as carriers of the elements through the air. The element sulfur, for example, is carried from the ocean to the land by dimethyl sulfide, a product of marine algae. In the Archean, the environment was either oxygen-free or there was an excess of reducing gases over oxygen. In such an atmosphere, the synthesis of dimethyl sulfide, which seems to take place only in oxic environments, is unlikely. Compounds such as hydrogen sulfide and carbon disulfide, which are unstable in our present oxidizing air, could have served instead to carry the essential element sulfur, also in the Archean land life could have needed less.

Hydrogen sulfide is ubiquitous in the anoxic zones and reacts with many metals -- such as lead, silver, and mercury -- that might otherwise accumulate to toxic levels. The result is water-insoluble sulfides that settle as solids. The geochemist Wolfgang Krumbein has shown that the ore beds of these elements exposed on or near the surface today are the waste tips of some past anoxic ecosystem. Anaerobic organisms that converted the potentially toxic elements, mercury and lead, to their volatile methyl derivatives grew successfully and provided the ecosystem with a mechanism to remove toxic waste. The anoxic zones are continuously perfused by a flow of methane gas that would serve to carry these volatile materials away from the region. Some of this methylating activity is beneficial on a regional or even global scale. The production of dimethyl selenium serves in a subtle way, first discovered by the atmospheric chemist F. S. Rowland, to offset the toxicity of dimethyl mercury. It also acts to recirculate the essential element selenium through the global environment.

The rate of carbon burial during the Archean was not significantly different from today. As we saw earlier, the carbon present in the earliest sedimentary rocks shows a subtle difference in the proportion of its isotopes from that of lunar rocks that have never been exposed to life; this difference is evidence for the presence of photosynthesizers. The geologist Euan Nisbet tells me that there are Archean, carbon-rich shale deposits in southern Africa. They are like the coal measures put down by the forest trees of the Carboniferous period, eons later. These carbon deposits are all that remains of the dead bodies of microorganisms that once grew in the Archean. Volcanoes then, as now, vented carbon dioxide. Archean photosynthetic and other bacteria used this carbon dioxide to make the organic compounds of their cells; these organisms also may have facilitated the reaction of carbon dioxide with calcium and other divalent ions dissolved in the sea and on the land surfaces. These two reactions were the sinks for carbon dioxide and kept a steady level in the atmosphere. This is part of the climate regulating system illustrated in figure 4.2. In addition to these climatic consequences, the Archean ecosystems would have buried a small but constant proportion of their carbon turnover, which would have led to the steady addition of oxygen. This, however, would have been used up in oxidizing the reducing compounds of the surface and ocean environments, and that emitted by volcanoes. It was somewhat like one of those chemistry experiments in high school, where you progressively add an oxidizing solution to a reducing solution until an indicator suddenly changes color to mark the equally sudden change from reducing to oxidizing at the end of the titration. The burial of a small proportion of the carbon and sulfur, cycled by once-living bacteria, titrated the oxidizable material of the environment until the surplus was used up. Reducing material continued to be added to the ocean and the atmosphere, but the rate of its addition became less than that of carbon burial. Free oxygen gas began to appear in the air at levels more than sufficient to overcome the reducing tendency of methane, and marked the end of the epoch.

It seems likely that the end of the period when methane dominated the chemistry of the atmosphere was abrupt. But it would be wrong to envisage a sudden change from a wholly oxygen-free world to one where oxygen was present free in the air. Much more probable is the gradual growth during the latter part of the Archean of oxic organisms at the surface of the Earth. These could have existed first at the surface, where the phototrophs basked in the sunlight and locally produced enough oxygen to support them. They would be a separate and encapsulated ecosystem surviving in an otherwise lethal system, rather as the anaerobes survive in the poisonous oxygen-rich world of today. In this oxic ecosystem there would be consumers living on organic products of the cyanobacteria, and also organisms able to exploit a slightly oxidizing medium and perform such tricks as denitrification (using nitrate and nitrite ions instead of oxygen, so that nitrogen escaped to the air as gaseous nitrogen and nitrous oxide).

Gradually, as the oxygen-scavenging compounds of the sea were used up, the oxygen released by the phototrophs would no longer be absorbed. Then the ratio of the methane to oxygen flux to the atmosphere would shift towards an oxygen excess. The oxic ecosystems would spread and, just before free oxygen increased in abundance to become the dominant oxidizer, would probably have covered most of the oceans. The changeover was not so much a genocide as a domination. Even stranger scenarios are likely if the surface communities generated nitrous oxide before oxygen itself appeared. This gas is stable in the troposphere and might have allowed methane to persist longer; it is also somewhat of a greenhouse gas and might have compensated for the decline in methane. It is made by bacteria now, and it is likely that there were bacteria making it then.

In geophysiology, the Archean boundary coincided with the great punctuation marked by oxygen's free presence in the air. However, for the bacteria of the Archean the era never ended. They live on wherever the environment is free of oxygen. They run the vital and extensive ecosystems of the anoxic zones beneath the sea floor, in the wetlands and marshes, and in the guts of nearly all consumers including ourselves. In a strict geological sense, the period ended 2.5 eons ago, and oxygen may have come later. The appearance of oxygen in the air and on the surface of the oceans did not eliminate the anoxic ecosystems; it merely segregated them in the stagnant waters and sediments. As a consequence, the rocks that formed from these sediments may have failed to record the presence of free oxygen in the air.

That, then, is an account of a few aspects of the Archean seen through Gaia theory. It was a period when the Earth's operating system was populated wholly by bacteria. It was a long period, when the living constituents of Gaia could be truly considered as a single tissue. Bacteria are both mobile and motile, and could have moved around the world carried by winds and ocean currents. They can also readily exchange information, as messages encoded on low-molecular-weight chains of nucleic acids called plasmids. All life on Earth was then linked by a slow but precise communication network. Marshall McLuhan's vision of the "global village," with humans tied in a chattering network of telecommunication, is a re-enactment of this Archean device.

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Notes:

1. Those still skeptical might be persuaded by the reports of these experiments in the Medical Research Council's special report number 262, entitled "Studies in Air Hygiene" and published in 1948.
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