James Lovelock (1979)

James Lovelock

A new look at life on Earth

Source: Gaia A new look at life on Earth by J E Lovelock, publ. Oxford University Press 1979.


As I write, two Viking spacecraft are circling our fellow planet Mars, awaiting landfall instructions from the Earth. Their mission is to search for life, or evidence of life, now or long ago. This book also is about a search for life, and the quest for Gaia is an attempt to find the largest living creature on Earth. Our journey may reveal no more than the almost infinite variety of living forms which have proliferated over the Earth's surface under the transparent case of the air and which constitute the biosphere. But if Gaia does exist, then we may find ourselves and all other living things to be parts and partners of a vast being who in her entirety has the power to maintain our planet as a fit and comfortable habitat for life.

The quest for Gaia began more than fifteen years ago, when NASA (the National Aeronautics and Space Administration of the USA) first made plans to look for life on Mars. It is therefore right and proper that this book should open with a tribute to the fantastic Martian voyage of those two mechanical Norsemen.

In the early nineteen-sixties I often visited the Jet Propulsion Laboratories of the California Institute of Technology in Pasadena, as consultant to a team, later to be led by that most able of space biologists Norman Horowitz, whose main objective was to devise ways and means of detecting life on Mars and other planets. Although my particular brief was to advise on some comparatively simple problems of instrument design, as one whose childhood was illuminated by the writings of Jules Verne and Olaf Stapledon I was delighted to have the chance of discussing at first hand the plans for investigating Mars.

At that time, the planning of experiments was mostly based on the assumption that evidence for life on Mars would be much the same as for life on Earth. Thus one proposed series of experiments involved dispatching what was, in effect, an automated microbiological laboratory to sample the Martian soil and judge its suitability to support bacteria, fungi, or other micro-organisms. Additional soil experiments were designed to test for chemicals whose presence would indicate life at work: proteins, amino-acids, and particularly optically active substances with the capacity that organic matter has to twist a beam of polarised light in a counter-clockwise direction.

After a year or so, and perhaps because I was not directly involved, the euphoria arising from my association with this enthralling problem began to subside, and I found myself asking some rather down-to-earth questions, such as, 'How can we be sure that the Martian way of life, if any, will reveal itself to tests based on Earth's life style?' To say nothing of more difficult questions, such as, 'What is life, and how should it be recognised?'

Some of my still sanguine colleagues at the Jet Propulsion Laboratories mistook my growing scepticism for cynical disillusion and quite properly asked, 'Well, what would you do instead?' At that time I could only reply vaguely, "I'd look for an entropy reduction, since this must be a general characteristic of all forms of life." Understandably, this reply was taken to be at the best unpractical and at worst plain obfuscation, for few physical concepts can have caused as much confusion and misunderstanding as has that of entropy.

It is almost a synonym for disorder and yet, as a measure of the rate of dissipation of a system's thermal energy, it can be precisely expressed in mathematical terms. It has been the bane of generations of students and is direfully associated in many minds with decline and decay, since its expression in the Second Law of Thermodynamics (indicating that all energy will eventually dissipate into heat universally disturbed and will no longer be available for the performance of useful work) implies the predestined and inevitable run-down and death of the Universe.

Although my tentative suggestion had been rejected, the idea of looking for a reduction or reversal of entropy as a sign of life had implanted itself in my mind. It grew and waxed fruitful until, with the help of many colleagues, Dian Hitchcock, Sidney Epton, Peter Simmonds, and especially Lynn Margulis, it evolved into the hypothesis which is the subject of this book.

Back home in the quiet countryside of Wiltshire, after my visits to the Jet Propulsion Laboratories, I had time to do more thinking and reading about the real character of life and how one might recognise it anywhere and in any guise. I expected to discover somewhere in the scientific literature a comprehensive definition of life as a physical process, on which one could base the design of life-detection experiments, but I was surprised to find how little had been written about the nature of life itself. The present interest in ecology and the application of systems analysis to biology had barely begun and there was still in those days the dusty academic air of the classroom about the life sciences. Data galore had been accumulated on every conceivable aspect of living species, from their outermost to their innermost parts, but in the whole vast encyclopaedia of facts the crux of the matter, life itself, was almost totally ignored. At best, the literature read like a collection of expert reports, as if a group of scientists from another world had taken a television receiver home with them and had reported on it. The chemist said it was made of wood, glass, and metal. The physicist said it radiated heat and light. The engineer said the supporting wheels were too small and in the wrong place for it to run smoothly on a flat surface. But nobody said what it was.

This seeming conspiracy of silence may have been due in part to the division of science into separate disciplines, with each specialist assuming that someone else has done the job. Some biologists may believe that the process of life is adequately described by some mathematical theorem of physics or cybernetics, and some physicists may assume that it is factually described in the recondite writings on molecular biology which one day he will find time to read. But the most probable cause of our closed minds on the subject is that we already have a very rapid, highly efficient life-recognition programme in our inherited set of instincts, our 'read-only' memory as it might be called in computer technology. Our recognition of living things, both animal and vegetable, is instant and automatic, and our fellow-creatures in the animal world appear to have the same facility. This powerful and effective but unconscious process of recognition no doubt originally evolved as a survival factor. Anything living may be edible, lethal, friendly, aggressive, or a potential mate, all questions of prime significance for our welfare and continued existence. However, our automatic recognition system appears to have paralysed our capacity for conscious thought about a definition of life. For why should we need to define what is obvious and unmistakable in all its manifestations, thanks to our built-in programme? Perhaps for that very reason, it is an automatic process operating without conscious understanding, like the autopilot of an aircraft.

Even the new science of cybernetics has not tackled the problem, although it is concerned with the mode of operation of all manner of systems from the simplicity of a valve-operated water tank to the complex visual control process which enables your eyes to scan this page. Much, indeed, has already been said and written about the cybernetics of artificial intelligence, but the question of defining real life in cybernetic terms remains unanswered and is seldom discussed.

During the present century a few physicists have tried to define life. Bernal, Schroedinger, and Wigner all came to the same general conclusion, that life is a member of the class of phenomena which are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form. This definition is not only difficult to grasp but is far too general to apply to the specific detection of life. A rough paraphrase might be that life is one of those processes which are found whenever there is an abundant flow of energy. It is characterised by a tendency to shape or form itself as it consumes, but to do so it must always excrete low-grade products to the surroundings.

We can now see that this definition would apply equally well to eddies in a flowing stream, to hurricanes, to flames, or even to refrigerators and many other man-made contrivances. A flame assumes a characteristic shape as it burns, and needs an adequate supply of fuel and air to keep going, and we are now only too well aware that the pleasant warmth and dancing flames of an open fire have to be paid for in the excretion of waste heat and pollutant gases. Entropy is reduced locally by the flame formation, but the overall total of entropy is increased during the fuel consumption.

Yet even if too broad and vague, this classification of life at least points us in the right direction. It suggests, for example, that there is a boundary, or interface, between the 'factory' area where the flow of energy or raw materials is put to work and entropy is consequently reduced, and the surrounding environment which receives the discarded waste products. It also suggests that life-like processes require a flux of energy above some minimal value in order to get going and keep going. The nineteenth-century physicist Reynolds observed that turbulent eddies in gases and liquids could only form if the rate of flow was above some critical value in relation to local conditions. The Reynolds dimensionless number can be calculated from simple knowledge of a fluid's properties and its local flow boundaries. Similarly, for life to begin, not only the quantity but also the quality, or potential, of the energy flow must be sufficient. If, for example, the sun's surface temperature were 500 degrees instead of 5,000 degrees Centigrade and the Earth were correspondingly closer, so that we received the same amount of warmth, there would be little difference in climate, but life would never have got going. Life needs energy potent enough to sever chemical bonds; mere warmth is not enough.,

It might be a step forward if we could establish dimensionless numbers like the Reynolds scale to characterise the energy conditions of a planet. Then those enjoying, with the Earth, a flux of free solar energy above these critical values would predictably have life whilst those low on the scale, like the cold outer planets, would not.

The design of a universal life-detection experiment based on entropy reduction seemed at this time to be a somewhat unpromising exercise. However, assuming that life on any planet would be bound to use the fluid media-oceans, atmosphere, or both-as conveyor-belts for raw materials and waste products, it occurred to me that some of the activity associated with concentrated entropy reduction within a living system might spill over into the conveyor-belt regions and alter their composition. The atmosphere of a life-bearing planet would thus become recognisably different from that of a dead planet.

Mars has no oceans. If life had established itself there, it would have had to make use of the atmosphere or stagnate. Mars therefore seemed a suitable planet for a life-detection exercise based on chemical analysis of the atmosphere. Moreover, this could be carried out regardless of the choice of landing site. Most life-detection experiments are effective only within a suitable target area. Even on Earth, local search techniques would be unlikely to yield much positive evidence of life if the landfall occurred on the Antarctic ice sheet or the Sahara desert or in the middle of a salt lake.

While I was thinking on these lines, Dian Hitchcock visited the Jet Propulsion Laboratories. Her task was to compare and evaluate the logic and information-potential of the many suggestions for detecting life on Mars. The notion of life detection by atmospheric analysis appealed to her, and we began developing the idea together. Using our own planet as a model, we examined the extent to which simple knowledge of the chemical composition of the Earth's atmosphere, when coupled with such readily accessible information as the degree of solar radiation and the presence of oceans as well as land masses on the Earth's surface, could provide evidence for life.

Our results convinced us that the only feasible explanation of the Earth's highly improbable atmosphere was that it was being manipulated on a day-to-day basis from the surface, and that the manipulator was life itself. The significant decrease in entropy-or, as a chemist would put it, the persistent state of disequilibrium among the atmospheric gases-was on its own clear proof of life's activity. Take, for example, the simultaneous presence of methane and oxygen in our atmosphere. In sunlight, these two gases react chemically to give carbon dioxide and water vapour. The rate of this reaction is such that to sustain the amount of methane always present in the air, at least 1,000 million tons of this gas must be introduced into the atmosphere yearly. In addition, there must be some means of replacing the oxygen used up in oxidising methane and this requires a production of at least twice as much oxygen as methane. The quantities of both of these gases required to keep the Earth's extraordinary atmospheric mixture constant was improbable on an abiological basis by at least 100 orders of magnitude.

Here, in one comparatively simple test, was convincing evidence for life on Earth, evidence moreover which could be picked up by an infra-red telescope sited as far away as Mars. The same argument applies to other atmospheric gases, especially to the ensemble of reactive gases constituting the atmosphere as a whole. The presence of nitrous oxide and of ammonia is as anomalous as that of methane in our oxidising atmosphere. Even nitrogen in gaseous form is out of place, for with the Earth's abundant and neutral oceans, we should expect to find this element in the chemically stable form of the nitrate ion dissolved in the sea.

Our findings and conclusions were, of course, very much out of step with conventional geochemical wisdom in the mid-sixties. With some exceptions, notably Rubey, Hutchinson, Bates, and Nicolet, most geochemists regarded the atmosphere as an end-product of planetary out-gassing and held that subsequent reactions by abiological processes had determined its present state. Oxygen, for example, was thought to come solely from the breakdown of water vapour and the escape of hydrogen into space, leaving an excess of oxygen behind. Life merely borrowed gases from the atmosphere and returned them unchanged. Our contrasting view required an atmosphere which was a dynamic extension of the biosphere itself. It was not easy to find a journal prepared to publish so radical a notion but, after several rejections, we found an editor, Carl Sagan, prepared to publish it in his journal, Icarus.

Nevertheless, considered solely as a life-detection experiment, atmospheric analysis was, if anything, too successful. Even then, enough was known about the Martian atmosphere to suggest that it consisted mostly of carbon dioxide and showed no signs of the exotic chemistry characteristic of Earth's atmosphere. The implication that Mars was probably a lifeless planet was unwelcome news to our sponsors in space research. To make matters worse, in September 1965 the US Congress decided to abandon the first Martian exploration programme, then called Voyager. For the next year or so, ideas about looking for life on other planets were to be discouraged.

Space exploration has always served as a convenient whipping-boy to those needing money for some worthy cause, yet it is far less expensive than many a stuck-in-the-mud, down-to-earth technological failure. Unfortunately, the apologists for space science always seem over-impressed by engineering trivia and make far too much of non-stick frying pans and perfect ball-bearings. To my mind, the outstanding spin-off from space research is not new technology. The real bonus has been that for the first time in human history we have had a chance to look at the Earth from space, and the information gained from seeing from the outside our azure-green planet in all its global beauty has given rise to a whole new set of questions and answers. Similarly, thinking about life on Mars gave some of us a fresh standpoint from which to consider life on Earth and led us to formulate a new, or perhaps revive a very ancient, concept of the relationship between the Earth and its biosphere.

By great good fortune, so far as I was concerned, the nadir of the space programme coincided with an invitation from Shell Research Limited for me to consider the possible global consequences of air pollution from such causes as the ever-increasing rate of combustion of fossil fuels. This was in 1966, three years before the formation of Friends of the Earth and similar pressure-groups brought pollution problems to the forefront of the public mind.

Like artists, independent scientists need sponsors but this rarely involves a possessive relationship. Freedom of thought is the rule. This should hardly need saying, but nowadays many otherwise intelligent individuals are conditioned to believe that all research work supported by a multi-national corporation must be suspect by origin. Others are just as convinced that similar work coming from an institution in a Communist country will have been subject to Marxist theoretical constraint and will therefore be diminished. The ideas and opinions expressed in this book are inevitably influenced to some degree by the society in which I live and work, and especially by close contact with numerous scientific colleagues in the West. So far as I know, these mild pressures are the only ones which have been exerted on me.

The link between my involvement in problems of global air pollution and my previous work on life detection by atmospheric analysis was, of course, the idea that the atmosphere might be an extension of the biosphere. It seemed to me that any attempt to understand the consequences of air pollution would be incomplete and probably ineffectual if the possibility of a response or an adaptation by the biosphere was overlooked. The effects of poison on a man are greatly modified by his capacity to metabolise or excrete it; and the effect of loading a biospherically controlled atmosphere with the products of fossil fuel combustion might be very different from the effect on a passive inorganic atmosphere. Adaptive changes might take place which would lessen the perturbations due, for instance, to the accumulation of carbon dioxide. Or the perturbations might trigger some compensatory change, perhaps in the climate, which would be good for the biosphere as a whole but bad for man as a species.

Working in a new intellectual environment, I was able to forget Mars and to concentrate on the Earth and the nature of its atmosphere. The result of this more single-minded approach was the development of the hypothesis/ that the entire range of living matter on Earth, from whales to viruses, and from oaks to algae, could be regarded as constituting a single living entity, capable of manipulating the Earth's atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constituent parts.

It is a long way from a plausible life-detection experiment to the hypothesis that the Earth's atmosphere is actively maintained and regulated by life on the surface, that is, by the biosphere. Much of this book deals with more recent evidence in support of this view. In 1967 the reasons for making the hypothetical stride were briefly these:

Life first appeared on the Earth about 3,500 million years ago. From that time until now, the presence of fossils shows that the Earth's climate has changed very little. Yet the output of heat from the sun, the surface properties of the Earth, and the composition of the atmosphere have almost certainly varied greatly over the same period.

The chemical composition of the atmosphere bears no relation to the expectations of steady-state chemical equilibrium. The presence of methane, nitrous oxide, and even nitrogen in our present oxidising atmosphere represents violation of the rules of chemistry to be measured in tens of orders of magnitude. Disequilibria on this scale suggest that the atmosphere is not merely a biological product, but more probably a biological construction: not living, but like a cat's fur, a bird's feathers, or the paper of a wasp's nest, an extension of a living system designed to maintain a chosen environment. Thus the atmospheric concentration of gases such as oxygen and ammonia is found to be kept at an optimum value from which even small departures could have disastrous consequences for life.

The climate and the chemical properties of the Earth now and throughout its history seem always to have been optimal for life. For this to have happened by chance is as unlikely as to survive unscathed a drive blindfold through rush-hour traffic.

By now a planet-sized entity, albeit hypothetical, had been born, with properties which could not be predicted from the sum of its parts. It needed a name. Fortunately the author William Golding was a fellow-villager. Without hesitation he Recommended that this creature be called Gaia, after the Greek Earth goddess also known as Ge, from which root the sciences of geography and geology derive their names. In spite of my ignorance of the classics, the suitability of this choice was obvious. It was a real four-lettered word and would thus forestall the creation of barbarous acronyms, such as Biocybernetic Universal System Tendency/Homoeostasis. I felt also that in the days of Ancient Greece the concept itself was probably a familiar aspect of life, even if not formally expressed. Scientists are usually condemned to lead urban lives, but I find that country people still living close to the earth often seem puzzled that anyone should need to make a formal proposition of anything as obvious as the Gaia hypothesis. For them it is true and always has been.

I first put forward the Gaia hypothesis at a scientific meeting about the origins of life on Earth which took place in Princeton, New Jersey, in 1969. Perhaps it was poorly presented. It certainly did not appeal to anyone except Lars Gunnar Sillen, the Swedish chemist now sadly dead, and Lynn Margulis, of Boston University, who had the task of editing our various contributions. A year later in Boston Lynn and I met again and began a most rewarding collaboration which, with her deep knowledge and insight as a life scientist, was to go far in adding substance to the wraith of Gaia, and which still happily continues.

We have since defined Gaia as a complex entity involving the Earth's biosphere, atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet. The maintenance of relatively constant conditions by active control may be conveniently described by the term 'homoeostasis'.

Gaia has remained a hypothesis but, like other useful hypotheses, she has already proved her theoretical value, if not her existence, by giving rise to experimental questions and answers which were profitable exercises in themselves. If, for example, the atmosphere is, among other things, a device for conveying raw materials to and from the biosphere, it would be reasonable to assume the presence of carrier compounds for elements essential in all biological systems, for example, iodine and sulphur. It was rewarding to find evidence that both were conveyed from the oceans, where they are abundant, through the air to the land surface, where they are in short supply. The carrier compounds, methyl iodide and dimethyl sulphide respectively, are directly produced by marine life. Scientific curiosity being unquenchable, the presence of these interesting compounds in the atmosphere would no doubt have been discovered in the end and their importance discussed without the stimulus of the Gaia hypothesis. But they were actively sought as a result of the hypothesis and their presence was consistent with it.

If Gaia exists, the relationship between her and man, a dominant animal species in the complex living system, and the possibly shifting balance of power between them, are questions of obvious importance. I have discussed them in later chapters, but this book is written primarily to stimulate and entertain. The Gaia hypothesis is for those who like to walk or simply stand and stare, to wonder about the Earth and the life it bears, and to speculate about the consequences of our own presence here. It is an alternative to that pessimistic view which sees nature as a primitive force to be subdued and conquered. It is also an alternative to that equally depressing picture of our planet as a demented spaceship, forever travelling, driverless and purposeless, around an inner circle of the sun.


My father was born in 1872 and raised on the Berkshire Downs just south of Wantage. He was an excellent and enthusiastic gardener and also a very gentle man. I remember him rescuing wasps from drowning after they had blundered into the water butt. He would say, 'They are there for a purpose, you know, and then explain to me how they controlled the aphids on his plum trees and how they were surely due some of the crops as a reward.

He had no formal religious beliefs and did not attend church or chapel. I think his moral system came from that unstructured mixture of Christianity and magic which is common enough among country people, and in which May Day as well as Easter Day is an occasion for ritual and rejoicing. He felt instinctively his kinship with all living things and I remember how greatly it distressed him to see a tree cut down. I owe much of my own feeling for natural things to walks with him down country lanes and along ancient drives which had, or appeared in those days to have, a sweet seemliness and tranquillity.

This chapter begins autobiographically so that I may bring us the more easily to consider the most speculative and intangible aspects of the Gaia hypothesis: those which concern thought and emotion in the interrelationship of man and Gaia.

Let us start by considering our sense of beauty. By this, I mean those complex feelings of pleasure, recognition, and fulfilment, of wonder, excitement, and yearning, which fill us when we see, feel, smell, or hear whatever heightens our self-awareness and at the same time deepens our perception of the true nature of things. It has often been said-and for some, ad nauseam-that these pleasurable sensations are inextricably bound up with that strange hyperaesthesia of romantic love. Even so, there seems no need inevitably to attribute the pleasure we feel on a country walk, as our gaze wanders over the downs, to our instinctive comparison of the smooth rounded hills with the contours of a woman's breasts. The thought may indeed occur to us, but we could also explain our pleasure in Gaian terms.

Part of our reward for fulfilling our biological role of creating a home and raising a family is the underlying sense of satisfaction. However hard and disappointing at times the task may have been, we are still pleasurably aware at a deeper level of having played our proper part and stayed in the mainstream of life. We are equally and painfully aware of a sense of failure and loss if for some reason or other we have missed our way or made a mess of things.

It may be that we are also programmed to recognise instinctively our optimal role in relation to other forms of life around us. When we act according to this instinct in our dealings with our partners in Gaia, we are rewarded by finding that what seems right also looks good and arouses those pleasurable feelings which comprise our sense of beauty. When this relationship with our environment is spoilt or mishandled, we suffer from a sense of emptiness and deprivation. Many of us know the shock of finding that some peaceful rural haunt of our youth where once the wild thyme blew and where the hedges were thick with eglantine and may, has become a featureless expanse of pure weed-free barley.

It does not seem inconsistent with the Darwinian forces of evolutionary selection for a sense of pleasure to reward us by encouraging us to achieve a balanced relationship between ourselves and other forms of life. The thousand-year-old New Forest in southern England, once the private hunting reserve of William the Conqueror and his Norman barons, is still an area of great scenic beauty, where badgers roam at night - and ponies have right of way over humans and the internal combustion engine. Although this historic, 130-square-mile region of ancient woodland and heath is protected by special Acts of Parliament, the true price of its survival is our unceasing vigilance. For it is now the pleasure-ground of thousands of holiday picnickers, campers, and tourists, who drop 600 tons of litter annually and sometimes, with a careless match or cigarette, start fires which may destroy in a few hours over many acres the product of centuries-old balanced husbandry between the forester and his environment.

Another of our instincts which probably favours survival is that which associates fitness and due proportion with beauty in individuals. Our bodies are formed of cell co-operatives. Each nucleus-containing body cell is an association of lesser entities in symbiosis. If the product of all this co-operative effort, a human being, seems beautiful when correctly and expertly assembled, is it too much to suggest that we may recognise by the same instinct the beauty and fittingness of an environment created by an assembly of creatures, including man, and by other forms of life? Where every prospect pleases, and man, accepting his role as a partner in Gaia, need not be vile.

It would be dauntingly difficult to test experimentally the notion that the instinct to associate fitness with beauty favours survival, but it might be worth a try. I wonder if a positive answer would enable us to rate beauty objectively, rather than through the eye of the beholder. We have seen that the capacity greatly to reduce entropy or, to put it in the terms of information theory, greatly to reduce the uncertainty of the answers to the questions about life, is itself a measure of life. Let us set beauty as equal to such a measure of life. Then it could follow that beauty also is associated with lowered entropy, reduced uncertainty, and less vagueness. Perhaps we hare always known this, since it is after all part of our internal life recognition programme. Because of it we, through the eye of Blake, even saw our predator as beautiful:

Tiger! Tiger! burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?

In what distant deeps or skies
Burnt the fire of thine eyes?
On what wings dare he aspire?
What the hand dare seize the fire?

It might even be that the Platonic absolute of beauty does mean something and can be measured against that unattainable state of certainty about the nature of life itself.

My father never told me why he believed that everything in this world was there for a purpose, but his thoughts and feelings about the countryside must have been based on a mixture of instinct, observation, and tribal wisdom. These persist in diluted form in many of us today and are still strong enough to power environmental movements which have come to be accepted as forces to be reckoned with by other powerful pressure groups in our society. As a result, the churches of the monotheistic religions, and the recent heresies of humanism and Marxism, are faced with the unwelcome truth that some part of their old enemy, Wordsworth's Pagan, "suckled in a creed outworn", is still alive within us.

In earlier times, when plague and famine regulated our numbers, it seemed fair and fitting to try by every means to heal the sick and preserve human life. This attitude later crystallised into the rigidly uncompromising belief that the Earth was made for man and his needs and desires were paramount. In authoritarian societies and institutions, it seemed absurd to doubt the wisdom or propriety of razing a forest, damming a river, or building an urban complex. If it was for the material good of human beings, then it must be right. No moral question was involved, other than the need to prevent bribery and corruption and to ensure fair shares among the beneficiaries.

The pangs that many people now feel at the sight of dunes, salt-marshes, woodlands, and even villages brutally destroyed and erased from the face of the Earth by bulldozers are very real. It is no comfort to be told that this attitude is reactionary and that the new urban development will provide jobs and opportunities for young people. The fact that this answer is partly true increases the sense of pain and outrage by denying a right to express it. In such circumstances it is hardly surprising that the environmental movement, although powerful, has no clear-cut objective. It tends to attack quite viciously such inappropriate targets as the fluorocarbon industry and fox-hunting, while turning a blind eye to the potentially more serious problems posed by most methods of agriculture.

The strong but confused emotions aroused by the worst excesses of public works and private enterprise provide ripe material for exploitation by unscrupulous manipulators. Environmental politics is a lush new pasture for demagogues and therefore an increasing source of anxiety to responsible governments and industries alike. Attaching that overworked adjective 'environmental' to the names of departments and agencies dealing with various aspects of the problem seems unlikely to stem the rising tide of anger and protest.

Biological arguments which appear to have a sound scientific basis are often used to support environmental causes, but usually they carry very little weight with scientists. Ecologists know that so far there is no evidence that any of man's activities have diminished the total productivity of the biosphere. Whatever an ecologist may feel as an individual about an imminent problem, his hands are tied by a lack of hard scientific evidence. The result is an environmental movement which is thwarted, bewildered, and angry.

The churches and the humanist movements have sensed the powerful emotional charge generated by the environmental campaign and have re-examined their tenets and beliefs so as to take account of it. There is, for example, a fresh awareness of the concept of Christian stewardship whereby man, while still allowed dominion over the fish and the fowl and every living thing, is accountable to God for the good management of the Earth.

From a Gaian viewpoint, all attempts to rationalise a subjugated biosphere with man in charge are as doomed to failure as the similar concept of benevolent colonialism. They all assume that man is the possessor of this planet; if not the owner, then the tenant. The allegory of Orwell's Animal Farm takes on a deeper significance when we realise that all human societies in one way or another regard the world as their farm. The Gaia hypothesis implies that the stable state of our planet includes man as a part of, or partner in, a very democratic entity.

Among several difficult concepts embodied in the Gaia hypothesis is that of intelligence. Like life itself, we can at present only categorise and cannot completely define it. Intelligence is a property of living systems and is concerned with the ability to answer questions correctly. We might add, especially questions about those responses to the environment which affect the system's survival, and the survival of the association of systems to which it belongs.

At the cellular level, decisions as to the edibility or otherwise of things encountered, and as to whether the environment is favourable or hazardous, are vital for survival. They are, however, automatic processes and do not involve conscious thought. Much of the routine operation of homoeostasis, whether it be for the cell, the animal, or for the entire biosphere, takes place automatically, and yet it must be recognised that some form of intelligence is required even within an automatic process, to interpret correctly information received about the environment. To supply the right answers to simple questions such as: 'Is it too hot?' or: 'Is there enough air to breathe?' requires intelligence. Even at the most rudimentary level, the primitive cybernetic system discussed in chapter 4, which provides the correct answer to the simple question about the internal temperature of the oven, requires a form of intelligence. Indeed, all cybernetic systems are intelligent to the extent that they must give the correct answer to at least one question. If Gaia exists, then she is without doubt intelligent in this limited sense at the least.

There is a spectrum of intelligence ranging from the most rudimentary, as in the foregoing example, to our own conscious and unconscious thoughts during the solving of a difficult problem. We saw something of the complexity of our own body-temperature regulatory system in chapter 4, although we were mainly concerned with that part which is wholly automatic and does not involve conscious action. Compared with the thermostasis of a kitchen oven, the body's automatic temperature-regulating system is intelligent to the point of genius, but it is still below the level of consciousness. It is to be compared in intelligence with the level of the regulatory mechanisms which we would expect to find Gaia using.

With creatures who possess the capacity of conscious thought and awareness, and no one as yet knows at what level of brain development this state exists, there is the additional possibility of cognitive anticipation. A tree prepares for winter by shedding its leaves and by modifying its internal chemistry to avoid damage from frost. This is all done automatically, drawing on a store of information handed down in the tree's genetic set of instructions. We on the other hand may buy warm clothes in preparation for a journey to New Zealand in July. In this we use a store of information gathered by our species as a collective unit and which is available to us all at the conscious level. So far as is known, we are the only creatures on this planet with the capacity to gather and store information and use it in this complex way. If we are a part of Gaia it becomes interesting to ask: 'To what extent is our collective intelligence also a part of Gaia? Do we as a species constitute a Gaian nervous system and a brain which can consciously anticipate environmental changes?'

Whether we like it or not, we are already beginning to function in this way. Consider, for example, one of those mini-planets, like Icarus, a mile or so in diameter and with an irregular orbit intersecting that of the Earth. Some day the astronomers may warn us that one of these is on a collision course with the Earth and that impact will occur within, say, a few weeks' time. The potential damage from such a collision could be severe, even for Gaia. This kind of accident has probably happened to the Earth in the past and caused major devastation. With our present technology, it is just possible that we could save ourselves and our planet from disaster. There is no doubt of our capacity to send things through space over vast distances and to exercise remote control, with near-miraculous precision, of their movements. It has been calculated that by using some of our store of hydrogen bombs and large rocket vehicles to carry them, we have the capacity to deflect a planetoid like Icarus sufficiently to convert a direct hit into a near miss. If this seems like fantastic science fiction, we should remember that, in our lifetime, yesterday's science fiction has almost daily become factual history.

It might equally well happen that advances in climatology revealed the approach of a particularly severe glacial epoch. We saw in chapter 2 that although another Ice Age might be a disaster for us, it would be a relatively minor affair for Gaia. However, if we accept our role as an integral part of Gaia, our discomfort is hers and the threat of glaciation is shared as a common danger. One possible course of action within our industrial capacity would be the manufacture and release to the atmosphere of a large quantity of chlorofluorocarbons. When these controversial substances, now present in the air at one-tenth of a part per thousand million, are increased in concentration to several parts per thousand million, they would serve, like carbon dioxide, as greenhouse gases preventing the escape of heat from the Earth to space. Their presence might entirely reverse the onset of a glaciation, or at least greatly diminish its severity. That they might incidentally cause some damage to the ozone layer for a time would seem a trivial problem by comparison.

These are just two examples of possible large-scale emergencies for Gaia which we might in the future be able to help her resolve. Still more important is the implication that the evolution of homo sapiens, with his technological inventiveness and his increasingly subtle communications network, has vastly increased Gaia's range of perception. She is now through us awake and aware of herself. She has seen the reflection of her fair face through the eyes of astronauts and the television cameras of orbiting spacecraft. Our sensations of wonder and pleasure, our capacity for conscious thought and speculation, our restless curiosity and drive are hers to share. 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. It might seem to be a surrender, but I suspect that the rewards, in the form of an increased sense of well-being and fulfilment, in knowing ourselves to be a dynamic part of a far greater entity, would be worth the loss of tribal freedom.

Perhaps we are not the first species destined to fulfil such a role, nor possibly the last. Another candidate could be found among the great sea mammals, which have brains many times larger than ours. It is a commonplace of biology that functionless tissues reduce during the course of evolution. Passenger organs do not exist in self-optimising systems. It therefore seems probable that the sperm whale makes intelligent use of the vast brain it possesses, perhaps at thought levels well beyond our understanding. Of course it is possible that the whale's brain arose for some relatively trivial reason, for example as a multi-dimensional living map of the oceans. Certainly there is no more potent way of consuming memory space than the storage of data in multi-dimensional arrays. Or should we perhaps compare the whale's brain to the peacock's tail, a scintillating mental display organ for the purpose of attracting a mate and enhancing the pleasures of courtship: the whale who provides the most stimulating entertainment having the best choice of mates? Whatever the true explanation and however it came about, the real point about the whale and the size of its brain is that large brains are almost certainly versatile. The original cause of their development may be specific, but once they are in existence other possibilities inevitably become exploited. Human brains, for example, did not develop as a result of the natural selective advantage of passing examinations, nor indeed so that we could perform any of the feats of memory and other mental exercises now explicitly required for "education".

As a collective species with the capacity to store and process information, we have probably long surpassed the whale. We are, however, inclined to forget that very few of us as individuals could make an iron bar from iron ore, and still fewer of us could use the bars to make a bicycle. The whale as an individual entity may possess a capacity for thought at levels of intricacy far beyond our comprehension, and might even include among his mental inventions the complete specification of a bicycle; but denied the tools, the craft, and the permanent store of know-how, the whale is not free to turn such thought into hardware.

Although it is unwise to draw analogies between animal brains and computers, it is often tempting to do so. Let us succumb to this temptation and indulge the thought that we humans differ from all other animal species in the superabundance of accessories through which we can communicate and express our intelligence, both individually and collectively, and so use it to produce hardware and to modify the environment. Our brains can be likened to medium-size computers which are directly linked to one another and to memory banks, as well as to an almost unlimited array of sensors, peripheral devices, and other machines. By contrast, whale brains are like a group of large computers loosely linked to one another but almost bereft of any means of external communication.

What should we have thought of an early race of hunters who developed a taste for horsemeat and then proceeded to eliminate the horse from the Earth by systematically hunting and killing every one, merely to satisfy their appetite? Savage, lazy, stupid, selfish, and cruel are some of the epithets that come to mind; and what a waste to fail to recognise the possibility of the working partnership between horse and man! It is bad enough to cull or farm the whale so as to provide a constant supply of those products which whale-hunting nations claim are needed by their backward and primitive industries. If we hunt them heedlessly to extinction it must surely be a form of genocide, and will be an indictment of the indolent and hidebound national bureaucracies, Marxist and capitalist alike, which have neither the heart to feel nor the sense to comprehend the magnitude of the crime. Yet perhaps it is not too late for them to see the error of their ways. Perhaps one day the children we shall share with Gaia will peacefully co-operate with the great mammals of the ocean and use whale power to travel faster and faster in the mind, as horse power once carried us over the ground.