第3章

MOTHER NATURE OR MONSTER EARTH?

CHAPTER 1

Evolution's Motive Force

There is nothing conscious about life's lethal activities.

PETER WARD 2009

Whatever each day held, Charles Darwin tried to set aside time for a stroll around a 'sand walk' near his home, Down House, in Kent. Tradition has it that the sand walk was his thinking space-the place where he sharpened his evolutionary theory, as well as the sentences that would so elegantly carry it into print. Consequently, the walk is regarded with reverence by many scientists, and when I made my first pilgrimage to Down House in October 2009 it was this place above all that I wished to see. After paying my respects to the great man's office and drawing room, I followed the signs to the walk. It's a little removed from the house and its enclosed gardens, and entering it one feels instantly transported from the ordered human world into the wider world of nature.

The walk consists of an oval-shaped path around a forest of hazel, privet and dogwood planted by Darwin himself. I was surprised to discover that despite its name there is no sand on it, nor has there ever been. Instead, it is surfaced with flints, which Darwin's son Francis remembered his father kicking from the path as a means of keeping count of the number of circuits he'd completed. The forest is now tall and venerable, and as I strolled I found myself pondering the thoughts that might possess a man as he walked repeatedly-almost compulsively-on a course as regular as a racetrack, through what must then have been saplings. While we can't know what occupied Darwin on the sand walk, there are hints in notes left by his children. As they grew up they took to playing in the walk, and often distracted and delighted their father with their games. To a man immersed in complex reasoning, such disturbances would surely be resented, so perhaps complex theories or elegant sentences weren't the things that occupied him after all.

It's my guess that during this repetitious physical activity Darwin was mentally fingering his worry beads-and looming large among his concerns were the implications of the theory he is now famous for. Known today as evolution by natural selection, it explains how species, including our own, are created. Natural selection, Darwin understood from his studies, is an unspeakably cruel and amoral process. He came to realise that he must eventually tell the world that we are spawned not from godly love, but evolutionary barbarity. What would the social implications be? As his discovery became widely understood, would faith, hope and charity perish? Would England's early industrial society, already barbaric enough, become a place where only the fittest survived, and where the survivors believed this was the natural order? Might his innocent-sounding theory turn people into cold-blooded survival machines?

Charles Robert Darwin was born in 1809 in Shropshire, the son of a wealthy society doctor. Baptised into the Anglican Church, he was expected to follow his father into medicine. But the cruelty of surgery in the pre-anaesthetic era horrified him, so he quit his studies in favour of training as an Anglican parson, and in 1828 he enrolled in a Bachelor of Arts degree at Cambridge. This was the necessary prerequisite for a specialised course in divinity, and in his finals he excelled in theology, while barely scraping through in mathematics, physics and the classics. Darwin's plans for a life of bucolic vicardom, however, were deferred when, in August 1831, he heard that a naturalist was needed for a two-year voyage to Tierra del Fuego and the East Indies aboard the survey ship Beagle.

Although his father initially opposed the venture, Charles won him over and was accepted as a self-funded gentleman naturalist on the voyage. His most important duty, from the navy's perspective, was to provide Captain Robert Fitzroy-a man of rather melancholy temperament-with companionship. The voyage would stretch to five years, taking Darwin round the globe and exposing him to the extraordinary biodiversity and geology of South America, Australia and many islands. It was in the Galápagos archipelago that Darwin collected what would become vital evidence for his theory-species of birds and reptiles that had evolved on, and were unique to, specific islands. For any young man such a voyage would be formative, but for Darwin it was world-changing. He later said that 'the voyage of the Beagle has been by far the most important event in my life and has determined my whole career'.

The experience led Darwin to reject religion. He later described how he had struggled to hold onto his faith, even as exposure to other cultures and the wider world made it less and less plausible:

I was very unwilling to give up my belief; I feel sure of this, for I can well remember often and often inventing day-dreams of old letters between distinguished Romans, and manuscripts being discovered at Pompeii or elsewhere, which confirmed in the most striking manner all that was written in the Gospels. But I found it more and more difficult, with free scope given to my imagination, to invent evidence which would suffice to convince me. Thus disbelief crept over me at very slow rate, but was at last complete.[1]

Upon returning to England in 1836, Darwin was accepted immediately into the bosom of the Victorian scientific establishment, and he commenced working up his Beagle discoveries. In 1842, aged thirty-two, he purchased Down House and there embarked upon a long career as an independent, and independently wealthy, scientist. The property provided for all Darwin's needs, serving as both a laboratory and a family home. Relatively modest in size, Down House must have been alive with the sounds of Charles and Emma Darwin's seven surviving children, and at times it must have seemed crowded. There is nonetheless an orderliness to the house and grounds that marks them as laboratories, in which Darwin pursued every conceivable ramification of the theory of evolution by natural selection, from the pollination of orchids to the origins of facial expressions.

Such a life is for the scientist a kind of Nirvana, but Darwin's lot was not entirely a happy one. Soon after returning from the Beagle voyage he fell ill, and for the rest of his life was plagued with symptoms, including heart palpitations, muscle spasms and nausea, that increased as he anticipated social occasions. Down House became his refuge, its solitude sustaining him through years of relentless work, illness and psychological stress until his death in 1882. I have little doubt that his illness was partly psychological, and exacerbated by what he believed to be the moral implications of his theory-a theory he largely kept to himself for twenty years. Darwin had realised that new species arose by natural selection as early as 1838, but he didn't publish until 1858. 'It is like confessing a murder,' he confided to a fellow scientist when explaining his evolutionary ideas in a letter.

Down House is central to Darwin and the development of his theory, and to understand that extraordinary place one can do no better than to read Darwin's study of earthworms.[2] We might have earthworms in our gardens and compost bins, but few of us take the time to investigate them. For Darwin, however, they held a lifelong fascination. In many ways his worm monograph, which was his last book, is his most remarkable, documenting as it does experiments that ran continuously for almost three decades. Some of the worms lived in flowerpots, which were often kept inside Down House, and they seem to have become family pets. Certainly their individual personalities were appreciated, Darwin noting that some were timid and others brave, some neat and tidy while others were slovenly.

Eventually the entire Darwin family became involved in the worm experiments. I can picture Charles, surrounded by his children, playing the bassoon or piano to the worms in order to investigate their sense of hearing (they turned out to be entirely deaf), and testing their sense of smell (also alas rudimentary) by chewing tobacco and breathing on them, or introducing perfume into their pots. When Darwin realised that his worms disliked contact with cold, damp earth, he provided them with leaves with which to line their burrows, in the process discovering that they are expert practitioners of geometry (and indeed origami), for in order to drag and fold leaves efficiently, he noted, they must ascertain the shape of the leaf and grasp it appropriately. Darwin also provided his worms with glass beads, which they used to decorate their burrows in very pretty patterns. But, most importantly, he learned that worms profited from their experience, and that they were apt to be distracted from tasks by various stimuli he presented; and this, he believed, pointed to a surprising intelligence.

The sagacity and morality of worms were subjects Darwin never tired of. He concluded that wasps, and even fish such as pike, were far behind worms in their intelligence and ability to learn. Such conclusions, he said, 'will strike every one as very improbable', but:

It may be well to remember how perfect the sense of touch becomes in a man when born blind and deaf, as are worms. If worms have the power of acquiring some notion, however rude, of the shape of an object and of their burrows, as seems to be the case, they deserve to be called intelligent, for they then act in nearly the same manner as would a man under similar circumstances.[3]

The worm monograph is also important in another way. In it Darwin came as close as he ever would to a sense of how Earth as a whole works. He had brushed against this subject in one of his early scientific papers that dealt with atmospheric dust he had collected while on the Beagle. Darwin thought that it was from the Sahara and was headed to South America, where the many spores and other living things included in it might perhaps find a new home. He never expanded his study into a theory of how dust might affect Earth overall, unlike more holistic thinkers we shall soon encounter who saw in dust important clues as to how life influences our atmosphere and climate. Darwin waited over half a lifetime before approaching what today is called Earth systems science-the holistic study of how our planet works-and, when he did so, it was through the lens provided by worms.

Darwin described how worms occur in great density over much of England, and how they emerge in their countless thousands in the darkest hours, their tails firmly hooked in their burrow entrances, to feel about for leaves, dead animals and other detritus which they drag into their burrows. Through their digging and recycling they enrich pastures and fields, and so enhance food production, thereby laying the foundation for English society. And in the process they slowly bury and preserve relics of an England long past. Darwin examined entire Roman villas buried by worms, along with ancient abbeys, monuments and stones, all of which would have been destroyed had they remained at the surface; and he accurately estimated the rate at which this process occurs: about half a centimetre per year.

Darwin's monograph on worms reveals much of the man's temperament, and of his particular sense of humour. But it also highlights his strengths as a scientist-an ordered mind and immense patience. But patience can be a weakness too, and in the end it almost robbed Darwin of his future fame, for his dilatory approach to publishing the theory saw him nearly trumped by a man twenty years his junior, an unknown naturalist working in far-off Indonesia named Alfred Russel Wallace.

On 18 June 1858, Darwin received a letter from Wallace outlining a theory that described the way in which new species come into existence, and asking Darwin to transmit the manuscript to Charles Lyell, one of England's most eminent scientists, for publication. Darwin was devastated. 'I never saw a more striking co-incidence. If Wallace had my MS sketch written out in 1842 he could not have made a better short abstract,' wailed Darwin to his friend Lyell.[4] Only quick footwork by Lyell and another of Darwin's friends, the botanist Joseph Hooker, allowed Darwin's 'sketch' of 1842 and Wallace's paper to be published simultaneously by the Linnean Society of London on 1 July 1858.

As it was, neither Darwin's nor Wallace's paper attracted much immediate attention. In summarising the research published in the society's journal that year, President Thomas Bell was rather complimentary of the amount of botanical work completed, but lamented that the year 'had not, indeed, been marked by any of those striking discoveries which at once revolutionise, so to speak, the department of science on which they bear'.[5] To make an impression on the public, clearly something more was needed, and this Darwin produced the following year. On 24 November 1859 his book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life was published. It was an instant success, forever securing Darwin's supremacy as the great evolutionist.

Despite being largely ignored, Darwin's first effort at introducing his idea got to the heart of the matter. In his 1858 paper he wrote:

Can it be doubted, from the struggle each individual has to obtain subsistence, that any minute variation in structure, habits, or instincts, adapting that individual better to the new conditions, would tell upon its vigour and health? In the struggle it would have a better chance of surviving; and those of its offspring which inherited the variation, be it ever so slight, would also have a better chance. Yearly more are bred than can survive; the smallest grain in the balance, in the long run, must tell on which death shall fall, and which shall survive. Let this work of selection on the one hand, and death on the other, go on for a thousand generations, who will pretend to affirm that it would produce no effect?[6]

The essence of Darwin's insight is thus very simple. More are born than can survive, and those best fitted to the circumstances into which they are born are most likely to survive and breed. This selection of individuals, generation after generation, over the vastness of geological time, causes descendants to differ from their ancestors. There is no morality in this argument-no overall superiority of one individual, class or nation over another-for as the environment changes so do those selected as the 'fittest'. But it did reveal a terrible truth-the weak (poorly adapted) must die if evolution is to progress.

On that day in 1858 when his revolutionary idea was made known to the world, Darwin was unable to be with his assembled colleagues. He was instead mourning the death of his son, his namesake Charles. Always a frail child, Charles died of scarlet fever aged eighteen months. We can only imagine the mood in Down House that day. Infant death was far more common then, but not one whit less devastating. And the head of the family had just brilliantly elucidated the process that had rendered his child nothing but a cooling pile of flesh, food for worms. For Darwin, who believed that there was no hereafter and no God to comfort him in his grief, the blow must have been almost unbearable. And now he had to live with the thought that his theory might rob such comforts from the entire world.

It's hard to imagine, from today's perspective, the impact Darwin's book and theory had on society, but some sense of it can be gained from a debate held in Oxford's stately Zoology Museum in 1860. Arguing on Darwin's behalf was zoologist Thomas Huxley, later known as Darwin's bulldog, and opposing him was Samuel Wilberforce, the Bishop of Oxford, known as Soapy Sam on account of being one of the finest public speakers of his day. On the Origin of Species had been published just seven months earlier, splitting church and society. About a thousand people crowded between the skeletons, stuffed animals and mineral specimens to hear the bishop and the scientist slug it out. Hundreds more were turned away for lack of room, and Darwin, fast becoming a perpetual valetudinarian, was absent.

The critical moment came when Wilberforce took a cheap shot, asking whether Huxley was descended from an ape on his mother's or his father's side. This prompted an extraordinary response, which Alfred Newton, an eye-witness, described as follows:

This gave Huxley the opportunity of saying that he would sooner claim kindred with an Ape than with a man like the Bishop who made so ill a use of his wonderful speaking powers to try and burke, by a display of authority, a free discussion on what was, or was not, a matter of truth, and reminded him that on questions of physical science 'authority' had always been bowled out by investigation, as witness astronomy and geology.

He then got hold of the Bishop's assertions and showed how contrary they were to facts, and how he knew nothing about what he had been discoursing on.[7]

With the bishop embarrassed into silence, Admiral Robert Fitzroy, who had twenty-five years earlier been captain of the Beagle and Darwin's companion, rose to denounce Darwin's book and, 'lifting an immense Bible first with both hands and afterwards with one hand over his head, solemnly implored the audience to believe God rather than man'.[8] And there was the rub: Darwin, the erstwhile divinity student, was implying that ours is a Godless world, in which every kind of barbarity is condoned by nature.

Even today understanding of Darwin's theory remains mired in confusion and prejudice, and the mangled notions thus created have a malignant impact on society. Without doubt Darwin had settled upon an unfortunate subtitle for his work, for only upon reading the entire book would one discover that the 'favoured races' did not explicitly include the British ruling class. Almost immediately On the Origin of Species began to be used to justify the appalling social and economic inequalities of the Victorian era. The concept of the survival of the fittest was used to promote the notion that the misery of the poorest reflects the natural order. While Darwin must shoulder some of the blame for this, it's important to remember that it wasn't he who invented the term 'survival of the fittest', but the philosopher and libertarian Herbert Spencer, in 1864, who went on to apply Darwinian thought to his own social theories.[9] Darwin did however adopt the phrase in the fifth edition of On the Origin of Species, published in 1869.

There are other reasons for our partial failure to grasp Darwin's meaning, including religious and linguistic heritages. Nineteenth-century Christian dogma, with its insistence on literal creationism, survives into the twenty-first century, and although most mainstream religions have long accepted evolutionary theory (Darwin after all is buried in Westminster Abbey) opposition remains strong in some quarters. Just as importantly, the English language still lacks an easily understood term that elegantly conveys Darwin's insight. 'Evolution' hardly does the job. The word's Latin origins refer to the unrolling of a manuscript, and it's more of a magician's black box or cartoon caricature than an explanation to most people. Interestingly, Darwin himself hardly ever used the word, preferring 'descent with modification'.

Not all societies, however, are so handicapped. In 1898, the scholar Yan Fu translated Thomas Huxley's 1893 book Evolution and Ethics into Chinese. The Darwinian theories of human evolution expounded therein found ready acceptance in China, in part perhaps because they reflect some traditional Chinese folk beliefs about the stages of human development, which involve a progression from foraging, cave-dwelling ancestors to fire-using and house-building ones, and then to agricultural beings. In his translation, Yan Fu rendered the word 'evolution' as tian yan. Chinese characters can be read in several ways, and one way of reading these characters is as 'heavens' performance'-the heavens in this instance meaning all of creation.[10]

Yan Fu's phrase is now obscure and defunct, but heavens' performance strikes me as a beautiful and illuminating way of describing Darwin's discovery, for evolution is indeed a sort of performance, one whose theme is the electrochemical process we call life and whose stage is the entire Earth. Funded by the Sun, heavens' performance has been running for at least 3.5 billion years, and barring cosmic catastrophe will probably run for a billion more. It's an odd sort of performance, though, for there are no seats but on the stage itself, and the audience are also the players. Darwin's genius was to elucidate, with elegant simplicity, the rules by which the performance has unfolded.

One reason for the broad appeal of Darwin's ideas in the nineteenth and twentieth centuries is evident in the opening lines of his famous 1858 essay, with its reference to the Swiss botanist Augustin Pyrame de Candolle:

De Candolle, in an eloquent passage, has declared that all nature is at war, one organism with another, or with external nature. Seeing the contented face of nature, this may at first well be doubted; but reflection will inevitably prove it to be true.[11]

War of course was one of the main occupations and passions of Victorian England, and the British excelled at it-the result being the greatest empire the world had ever seen. If nature favoured the militarily triumphant, then the Englishman must be a superior creature indeed. In an imperial age and aided by the works of Spencer, Darwin's explanation of evolution would give rise to an extraordinary plethora of social phenomena, many of which strayed far from the original. Such beliefs are known as social Darwinism and, from colonial-era expressions like 'shouldering the white man's burden' and 'soothing the pillow of a dying race', and on to eugenics, they permeated the cultural and intellectual fabric of the era.

During the early part of the twentieth century the appeal of such thinking only strengthened. Indeed, by the 1930s and '40s social Darwinism was informing extermination and selective breeding programs in Nazi Germany, while in the US contributors to the journal Eugenics were arguing for the mass sterilisation of those they felt were inferior, as well as publishing ridiculous family pedigrees of the movement's leaders in an attempt to position them as the fathers of a future superior American race. Allied victory in World War II largely destroyed the credibility of these extremists and their programs, but some versions of social Darwinism continue to be influential. Notions about the 'survival of the fittest' are exemplified by Margaret Thatcher's comment in 1987 that 'there is no such thing as society' (by which she presumably meant that each should look after his own).[12] They are also evident in the field of neoclassical economics, with its belief that an unregulated market best serves humanity's interests.

Perhaps Charles Darwin, as he trod his sand walk, foresaw the possibility of all of this, or perhaps not. In any case, late in life he wrote, 'I feel no remorse for having committed any great sin but have often and often regretted that I have not done more direct good to my fellow-creatures.'[13]

CHAPTER 2

Of Genes, Mnemes and Destruction

It would have been strange if philosophers and naturalists had not been struck by the similarity existing between the reproduction in offspring…and that other kind of reproduction we call memory.

RICHARD SEMON 1921

Evolutionary theory has progressed enormously since Darwin's day, and without doubt the most important contribution has come from the discovery of the mechanism of inheritance-of genes, the structure of DNA, and genomes. The science that resulted from this fusion of Darwin's theory with genetics is called Neo-Darwinism, and its greatest exponent is Richard Dawkins. In The Selfish Gene, published in 1976, Dawkins outlines his thesis that the gene is the basic unit of natural selection. It has proved to be one of the most productive evolutionary insights ever, clarifying many aspects of Darwinian theory. In essence Dawkins argues that natural selection does not act primarily on us as whole organisms, but on each of the roughly twenty-three thousand genes that constitute the blueprint for our bodies. His work raises, in perhaps an even more acute manner than Darwin ever did, the moral dilemma that lies at the heart of Darwinism, for a central pillar of his reasoning is that we and other animals are mere 'survival machines' whose sole purpose is to ensure the perpetuation of the genes we carry.[14]

The defining quality of a successful gene, Dawkins believes, is 'ruthless selfishness'. In this he is a direct intellectual descendant of de Candolle, except that he believes the 'war' is being waged not only all around us, but inside our bodies as well. Indeed Dawkins' theory predicts that genes and the bodies they create are in competition. It explains, for example, why male spiders allow themselves to be eaten by females after mating (because it's good for the spider's genes), and why 'death genes' (that can kill individual organisms) exist in certain species. Musing on Tennyson's famous phrase, Dawkins says that 'I think "nature red in tooth and claw" sums up our modern understanding of natural selection admirably'.[15]

Dawkins has a genius for exposing the evolutionary mechanisms that lie hidden within us, and in doing so he highlights the limits of reductionist science in comprehending the complexity that is us. Consider his musings on maternal care:

The sight of her child smiling, or the sound of her kitten purring, is rewarding to a mother, in the same sense as food in the stomach is rewarding to a rat in a maze. But once it becomes true that a sweet smile or a loud purr are rewarding, the child is in a position to use the smile or the purr in order to manipulate the parent, and gain more than its fair share of parental investment.[16]

It is not that this is wrong, only that Dawkins' mechanistic description of maternal love is inadequate to comprehend the profound relationship that exists between a mother and child. To thrive, a child must experience unconditional love, and a mother must feel that she is doing more than seeking rewards. No better illustration exists of why we cannot develop a satisfactory understanding of ourselves through selfish gene theory alone. We are far too complex to be comprehended through a reductive dissection of our parts.

We have a tendency to use ideas such as selfish gene theory to justify our own selfish and socially destructive practices. It's significant, I think, that Dawkins' book received wide acclaim on the eve of the 1980s-the era when greed was seen as good, and when the free market was worshipped. As our experience with social Darwinism illustrates, we need to be eternally on guard against the siren song of self-interest if we wish to live in a fair and equitable society.

Genes and ideas share at least one similarity: both reproduce, and the occasional error in reproduction provides variation. Thus, both are potentially subject to evolution by natural selection. Recognition that genes (or at least the physically inherited traits they give rise to) and ideas are similar is at least a century old. The German biologist Richard Semon wrote two books on the subject: Die Mneme (1904, published in English as The Mneme in 1921) and Die Mnemischen Empfindungen (1909, published in English as Mnemic Psychology in 1923).[17] He coined the word mneme (pronounced 'mnee-m', and which is derived from the Greek word for memory) to denote a grand unifying theory of reproduction-both physical and mental. He believed that memory had a physical reality, that it must leave an impression upon the brain. In describing his theory Semon wrote that:

Instead of speaking of a factor of memory, a factor of habit, or a factor of heredity…I have preferred to consider these as manifestations of a common principle, which I shall call the mnemic principle.[18]

Semon's work catalogues a fascinating if all but forgotten episode in twentieth-century biology which sought to prove that experience could be inherited. He drew heavily on the work of Paul Kammerer, a brilliant young Viennese biologist whose experiments with what he called the fire-newt (Salamandra maculosa) were considered sensational at the time. Pregnant females were kept from water, thereby inducing them to give birth to fewer, more advanced young. This characteristic, it was claimed, was passed on to the next generation, despite their having free access to water. Other experiments, conducted by Marie von Chauvin on axolotls, resulted in the creatures developing lungs. Their offspring, she observed, frequently surfaced to gulp air, something normal axolotls will do 'only at an advanced age and in water deficient in air'.[19] But there was always the possibility that genetics, rather than Semon's 'mnemic principle', influenced the result.

Irrefutable proof, Semon felt, was at last obtained by the indefatigable Herr Kammerer. His triumph with the 'obstetric toad' (Alytes obstetricans) consisted of persuading the warty creatures to forgo having sex on land by keeping them 'in a room at high temperature…until they were induced…to cool themselves in the water-trough…Here the male and female found each other'. Forced to mate in water rather than on land, the toads coupled in a manner not usually favoured by the species.[20] This Semon interpreted as the creatures 'remembering' the ancestral method of copulation, which, it was claimed, persisted in subsequent generations.

Some of the experiments supposedly demonstrating the mnemic principle were truly bizarre. Dr Walter Finkler devoted himself to transplanting the heads of male insects onto females. The victims showed signs of life for several days but, perhaps unsurprisingly, exhibited disturbed sexual behaviour. Dr Hans Spemann made the 'Bombinator' frog grow eye lenses on the back of its head-a feat surpassed by Dr Gunnar Ekman, who induced green tree frogs (Hyla arborea) to grow eye lenses anywhere 'with the possible exception of the ear and nose primordia'.[21] This, Semon was convinced, demonstrated that frog skin 'remembered' how to grow eyes if appropriately stimulated.

By the 1920s the body of work Semon drew upon was under assault. The geneticists, championed by William Bateson (the originator of the term genetics itself), launched attacks that seem to have been vitriolic and obsessive. It has been suggested that Bateson had personal reasons for wishing to see Kammerer's work discredited, and when, in 1926, it was discovered that one of Kammerer's toads had been tampered with, this was held up as evidence that his entire body of work was suspect. With his reputation in tatters, Kammerer shot himself.[22]

Semon's all-encompassing theory did indeed have a fatal flaw: it necessitated a Lamarckian element in physical evolution. One of the iron-clad rules of physical evolution is that individuals cannot pass on to their offspring any favourable traits acquired during their lifetimes. Lamarck believed that giraffes could stretch their necks by continually reaching up for leaves, and that such stretched necks could be passed on to their offspring. Today we know that neck length among giraffes is coded in their genes, and that, with some rare exceptions (such as lengths of DNA inserted into genomes by viruses), physical traits acquired during an individual's lifetime cannot be passed on. Cultural evolution, in contrast, is purely Lamarckian. It is fuelled by the spread of ideas, and technologies that flow from such ideas, and those acquired by one generation are passed on to the next. Cultural evolution is far faster than physical evolution: it took the sabre-toothed cats millions of years to evolve their great stabbing canines, but it took humans only a few thousand years to develop metal daggers that are far more potent weapons.

For all its flaws, Semon's pioneering work held a seed of genius that is built upon in Richard Dawkins' book The Selfish Gene. Dawkins proposes the term 'meme' for transmitted ideas or beliefs. He says of them that, 'if memes in brains are analogous to genes they must be self-replicating brain structures, actual patterns of neuronal wiring-up that reconstitute themselves in one brain after another', adding that 'memes should be regarded as living structures, not just metaphorically but technically'.

In summary, Dawkins' memes are ideas that have a physical reality in our brains. They are transferrable just as genes are, and he suggests that they may be similarly selfish. Just how closely analogous mnemes (I prefer Semon's spelling) and genes are is an open question, but I do not believe that mnemes are necessarily selfish in the way that genes are. Some mnemes, for example, can see individuals act against their strict self-interest. Philanthropists often donate their wealth to causes that benefit humanity or the environment, and sometimes they do so anonymously, thereby ensuring that they accrue no social benefit. Perhaps they give to such causes simply because they believe it's the right thing to do. Whatever the case, such philanthropy is not in the interest of their selfish genes, which would benefit maximally if all was given to their children or near relatives.

Some mnemes, however, do prompt people to act selfishly, but such mnemes are decried in all societies. Indeed our strongest moral and religious precepts are aimed squarely at destroying them. As we've seen, such mnemes thrive at times, not least when given credibility by social Darwinism or Neo-Darwinian theory. Viewed in this light, the conflict between religion and evolutionary theory looks somewhat different. The challenge to religious belief that Darwinism presented in Victorian Britain acted as a kind of 'secret weapon' for the cause of selfish mnemes. By eroding religious authority it diminished, for some at least, a belief in the need for 'good works'. I find it interesting that our leading Neo-Darwinian, Richard Dawkins, is now engaged in a crusade against religion. Will this crusade leave in its wake a society in which it is more likely that ideas about selfish genes carry undue influence?

Selfish gene theory predicts that, in conflicts between genes and the bodies they create, genes will almost always prevail. But with the evolution of the mneme, all of that has changed. Humans have developed the idea (itself a mneme) of genetic engineering. The technology potentially allows us to snip genes we don't like out of our genomes. Clearly, in our modern age mnemes trump genes. Indeed mnemes are the most powerful things in the world. Around two hundred years ago a man called James Watt developed a mneme involving coal, steam and movement-and as a result the very composition of Earth's atmosphere today is changed.

It's often said that there are two fundamental sentiments that decide an election-hope for the future, and fear of it. If hope prevails, we're likely to elect more generous governments and reach out to the world, but if fear prevails, we elect inward-looking, nationalistic ones. Factors determining the successful spread of mnemes are clearly extremely complex, but at the broadest level it does seem that we, collectively and as individuals, gravitate towards one of these two tendencies. If we believe that we live in a dog-eat-dog world where only the fittest survive, we're likely to propagate very different mnemes from those that arise from an understanding of the fundamental interconnectedness of things. In large part, our future as a species will be determined by which of these mnemes prevails.

A reductionist view of evolution remains strong within the life sciences-and there's been a recent resurgence of interest in the power of Darwinian competition 'red in tooth and claw' to explain Earth history. The Medea hypothesis of palaeontologist Peter Ward is named after the terrifying Medea of Greek mythology. Granddaughter of the Sun god Helios, she married Jason (he of the golden fleece), by whom she had two children. When Jason left her for Glauce, Medea extracted revenge by killing both of her children, after murdering Glauce and her father. Ward thinks that life is equally bloody and self-destructive, arguing that species will, if left unchecked, destroy themselves by exploiting their resources to the point of ecosystem collapse.[23] The Medea hypothesis in fact suggests that ruthless selfishness is inevitably a recipe for the elimination of a species. It argues that if we compete too successfully we will destroy ourselves.

Examples of Medean outcomes include the introduction of foxes into Australia in the nineteenth century, where they became so successful that they caused the extinction of twenty-odd native mammals that were their prey. If the settlers had not introduced rabbits, which the foxes also ate, the fox population would have suffered a catastrophic collapse. Easter Island offers another example. In this case humans destroyed the things their survival depended on, all the trees and birds, leading to population collapse and near extinction of people on the island.

Ward argues that the Medea hypothesis can explain the great extinction episodes of Earth's prehistory, and he sees the current destructive path of our human species as a continuation of that process. A key mechanism Ward identifies in causing these extinctions is the disruption of the carbon cycle by living things. One way this can occur is through what he calls 'greenhouse mass extinctions', which may be triggered if atmospheric carbon dioxide (CO2) levels exceed a thousand parts per million. Essentially, Ward believes, the warming caused by CO2 slows ocean circulation, depriving the ocean depths of oxygen. This allows sulphur bacteria (which don't need oxygen to live) to proliferate. Eventually oceanic oxygen levels drop so low that the sulphur bacteria reach the sunlit surface waters. There they release hydrogen sulphide (H2S) into the atmosphere, destroying the ozone layer and poisoning life on land. With both sea and land devastated, up to 95 per cent of all species can become extinct, as happened 250 million years ago at the end of the Permian period.

But there are problems with this hypothesis, for it's not clear that the major extinctions which punctuate Earth's history were in fact caused by living things. Indeed some, such as the asteroid-induced extinction that carried off the dinosaurs, Ward acknowledges, were clearly not. Much more research on extinction events is required before Ward's hypothesis can be uncritically accepted. And of course it's important to understand that most species exist, most of the time, without destroying themselves or their ecosystems. But even if some extinctions-whether planetary or local-are caused by life itself, does that prove that we, Medea-like, are destined to destroy most other life, condemning our descendants to a new dark age, or outright extinction?

Perhaps the most important thing that the Medea hypothesis tells us is that Spencer's notion of the survival of the fittest should be turned on its head. If Ward is correct, then the fittest are merely engines of self-destruction, which through their success ultimately obliterate both themselves and most of the species they coexist with. Medea is also a deeply dismaying hypothesis, implying as it does that life has no choice: we must either thrive by destroying others or be destroyed ourselves in turn. In this manifestation, the Medea hypothesis represents a synthesis of Neo-Darwinism and an awareness of the limits and fragility of our environment.

Considering the deep contradictions between our popular ideas of survival of the fittest and Medean catastrophism, you could take the view that our belief systems are doomed to swing incoherently between winner-takes-all theories of life and doomsday hypotheses. We will never understand our relationship to the planet that is our home unless we sort through these contradictions. But there has always been another approach, one that describes the evolutionary process as a series of win-win outcomes that has created a productive, stable and cooperative Earth-and its origins can be found with the co-founder of evolutionary theory, Alfred Russel Wallace.

CHAPTER 3

Evolution's Legacy

He who opens his eyes to the possibilities of evolution in their endless variety will abhor fraud and violence and disdain prosperity at the expense of his fellow creatures.

SVANTE ARRHENIUS 1909

Despite the fact that Charles Darwin and Alfred Russel Wallace independently hit upon the theory of evolution by natural selection, two more different men there never were. Darwin was a patient, methodical toiler, a scientist in the finest reductionist tradition. Wallace, in contrast, was a great synthesiser of all he saw and sensed, whose ideas came as flashes of genius. His description of the evolutionary process was dashed off in a few hours while he was in the grip of a malarial fever on the island of Ternate, in what is now Indonesia, yet it is the intellectual equal to Darwin's painstaking effort. In summarising his theory Wallace said:

There is a tendency in nature to the continued progression of certain classes of varieties further and further from the original type…This progression, by minute steps, in various directions, but always checked and balanced by the necessary conditions, subject to which alone existence can be preserved, may, it is believed, be followed out so as to agree with all the phenomena presented by organised beings, their extinction and succession in past ages, and all the extraordinary modifications of form, instinct, and habits which they exhibit.[24]

Darwin could hardly have put it better, but it's what Wallace did with his life after 1858 that sets him apart-for while Darwin sought enlightenment by studying smaller and smaller pieces of life's puzzle, Wallace took on the whole, trying to make sense of life at a planetary and universal scale. As he aged Wallace would, I think, have increasingly appreciated Yan Fu's translation of evolution as heavens' performance.

Born in Wales in 1823, Wallace was a product of the working class, and he embodies as much as anyone the aspiration for self-improvement characteristic of the age. Withdrawn from school because his family was unable to pay the fees, he joined his elder brother as an apprentice builder before an economic downturn left him briefly unemployed. Then, in 1848, he set off for Brazil to work as a collector of natural history specimens. In this he was fantastically successful, but as he was returning home laden with butterflies, birds and beetles sufficient to set him up for life, disaster struck. It began with the captain of the vessel that was carrying him and his collection emerging on deck. 'I'm afraid the ship's on fire,' he said. 'Come and see what you think of it.'[25] There was little time to think, however. The hold was filled with highly flammable palm oil, and Wallace could only grab a box containing a few drawings, clothes and one diary, before leaping into a lifeboat. Everything else, including his extensive scientific notes and magnificent collections, was lost. After ten days adrift in the mid-Atlantic the survivors were picked up by another vessel, but its provisions were exhausted, so the men were reduced to catching the ship's rats for food, and even consumed the contents of the grease pot. Just when it seemed that things could get no worse, another disaster struck the emaciated, rag-clad survivors. When almost in the English Channel, the ship was caught in a tremendous gale and, by the time it limped into London, sea water more than a metre deep had collected in the hold. Escaping a second shipwreck by a hair's breadth, Wallace arrived home penniless and looking like a castaway. He was soon forced by economic necessity to return to the tropics. This time he went to the East Indies, where he would remain until 1862, amassing collections and discoveries sufficient for enduring fame.

If Darwin was at the centre of the scientific establishment, Wallace was perpetually on its margin. Self-educated and perhaps not sceptical enough in some matters, he infamously became the dupe of spiritualists, his patronage giving credibility to their sleight-of-hand tricks that promised to put people in touch with the dead. He vehemently opposed vaccination on the eminently sensible grounds that there were risks involved in transmitting bodily matter between species and individuals. But he failed to see that even in that age of rudimentary hygiene the benefits of inoculation far outweighed the risks, and the medical establishment excoriated him for slowing vaccination's public acceptance. Later in life Wallace came to believe that the raison d'etre of the Universe was the development of the human spirit, a view widely mocked as na?ve and anthropocentric.

All of this was sufficient reason for the Victorian elite to exclude this self-made scientist, but Wallace was objectionable for another reason, one which struck at the very source of their wealth. One of his chief preoccupations was the air pollution then choking Britain's cities. He believed that 'the vast manufacturing towns belching forth smoke and poisonous gases' were stunting the bodies of working-class children, and indeed they were, carrying countless thousands prematurely to their graves.[26] An activist for social justice all his days, Wallace argued that this pollution persisted because of 'criminal apathy'.

Wallace lived to be ninety and, as he aged, his mind turned increasingly to the question of how the Earth as a whole works. Man's Place in the Universe-one of his last books, published in 1904, when he was eighty-has as its principal objective to demonstrate that life is unique to Earth, other planets such as Venus and Mars being dead.[27] It is perhaps the foundation text of astro-biology. Wallace elucidates the importance of the atmosphere to life in chapters such as 'Clouds, Their Importance and Their Causes' and 'Clouds and Rain Depend upon Atmospheric Dust'. And it is in this seemingly trivial matter of atmospheric dust that we see a difference between Darwin and Wallace: for Darwin it remained merely a phenomenon of zoogeographic interest, helping to explain the distribution of microorganisms, while Wallace saw it as an absolutely essential element in the Earth system, responsible for the blessings of rain and clouds, and, as such, deeply influential on the entire planet's climate. In describing the atmosphere as a whole, Wallace said:

It is really a most complex structure, a wonderful piece of machinery, as it were, which in its various component gases, its actions and reactions upon the water and the land, its production of electrical discharges, and its furnishing the elements from which the whole fabric of life is composed and perpetually renewed, may be truly considered to be the very source and foundation of life itself.[28]

Unlike Darwin, Wallace seems to have had no fear that an understanding of evolution would corrupt public morality-indeed he saw the evolutionary process, and our understanding of it, as potentially ushering in a wonderful future. I think that's because Wallace realised that while evolution by natural selection is a fearsome mechanism, it has nevertheless created a living, working planet, which includes us, with our love for each other, and our society. When I look out of the windows of my house near Sydney I can see the world of Wallace's vision. It is manifest in a graceful, pink-barked angophora tree that spreads a bounteous shade-a tree composed of billions of individual cells. Once, the ancestors of the chloroplasts that give its leaves their green colour were free-living bacteria. Then, aeons ago, they came to live within a single-celled, primitive plant. Today, so complete is the union of these once free-living and only remotely related organisms that most of us think of them as one, in this case a tree.

There is a more modest tree nearby called the scribbly gum, a whitish, twisted thing that bears an indecipherable script written by a beetle on its bark. The beetle cannot live without the tree, and the tree cannot live without an invisible partner, a fungus so humble that it cannot be seen, which sheaths intimately the scribbly gum's finest rootlets and improves the tree's access to nutrients. Fungus, beetle, bird, tree, and the human sitting in its shade, joyed by the song of the bird and the thought that a beetle has learned to write on bark. We are part of an interdependent community.

And then there is me. Billions of cells cooperating seamlessly at every moment and a brain made up of a reptilian stem, a middle mammalian portion, and two highly evolved yet relatively poorly connected hemispheres somehow add up to that thing I call me. And beyond that miracle of cooperation is my wider world, made up of a web of loves that I could not live without: spouse, children, parents, friends. Who is to say that a marriage cannot be any less complete a union than that between a chloroplast and the cell that hosts it? Beyond my family circle there is my city with its millions of residents, my country, which coordinates actions through a ballot box, and beyond that my planet with its countless dependent parts. Our world is a web of interdependencies woven so tightly it sometimes becomes love.

There are no doubt people who believe this cannot be, who argue that they inhabit a world ruled by intense competition in every domain of life, and that any semblance of love for our fellow man results only from God's good grace. True enough, competition exists, but it is 'the contented face of nature' that Darwin wrote of so sceptically that reigns most of the time. And from the love that sustains my family to the beetle that writes on the tree, every bit stems from evolution by natural selection.

If competition is evolution's motive force, then the cooperative world is its legacy. And legacies are important, for they can endure long after the force that created them ceases to be.

A clear illustration of the process that has created life as we know it can be found in a game of soccer. Anyone reading the sports pages might think that soccer is all about competition, but you've only got to see a match to learn how wrong that is. Soccer is a miracle of cooperation, and it's not just the teams that exist in extraordinary wholeness for that brief span between kickoff and final whistle. The eruption of emotion at a goal and the hushed silence at a last-minute free kick reveal a union of feeling in the spectators that lies at the very heart of the sport. After all, it's the sense of being part of this greater whole that gets the fans to the game each week, and without them the game would not exist. In sport, winners can survive only if losers do too; otherwise, there'd be no game. Our planet is rather similar. If a sufficiently superior and arrogant species arose and pursued a winner-take-all philosophy, it would be game over for us all. Alfred Russel Wallace, I believe, was the first modern scientist to comprehend how essential cooperation is to our survival.

I sometimes ponder what our world would be like if Wallace, rather than Darwin, had become the great scientific hero of the age. Would evolutionary theory have become the justification for an unjust society? Would evolution instead have been harnessed to an agenda of social reform? Would the sciences of ecology and astro-biology have emerged a century before they in fact did? Would air pollution and climate change have been defeated in the nineteenth century? We shall never know the answers to these questions. With the exception of a few, such as the Nobel Prize-winning chemist Svante Arrhenius, the scientific mainstream resisted most of Wallace's ideas. Ironically, he's best remembered for his zoogeography-the Wallace Line, a boundary that separates animal species in Australia and New Guinea from those in Asia.

Wallace was a profound thinker, yet his deepest ideas could not prosper in the brutal, imperial age in which he lived. But times change, and when in the 1970s a more powerfully explicatory theory of the type Wallace was groping at emerged, the world was at last prepared to listen.

The person who developed that theory was James Lovelock, and he did so, as far as I can determine, without knowledge of Wallace's work. Indeed, it's a remarkable fact that most of the researchers working in what we might call the Wallacean tradition of holistic, planetary-scale science seem to have arrived in the field more or less independently, unaware of the writings of their predecessors. Perhaps this is because the Wallaceans have rarely been part of the academic mainstream. Whatever the case, Wallace and Lovelock were both working-class outsiders of exceptional ability, and both saw that the atmosphere was the key to understanding life as a whole.

James Lovelock was born in Letchworth, outside London, in July 1919-a result, he believes, of the Armistice celebrations in November 1918. Although an indifferent student, by the age of twelve he had determined to become a scientist and began frequenting public libraries. James Jeans' Astronomy and Cosmogony, Frederick Soddy's The Interpretation of Radium and L. G. Wade's Organic Chemistry became his most cherished reading. It was at this time that he drifted from his agnostic upbringing and for a while became a Quaker with strong pacifist views. He studied chemistry at Manchester University, and, in 1941, got a job at the National Institute for Medical Research, where one of his principal responsibilities was investigating air hygiene in bomb shelters. An inventor of scientific instruments, he produced several devices to measure atmospheric composition, and so began a romance with the atmosphere that would last a lifetime.[29]

Lovelock tells us that the concept of Gaia came to him suddenly one afternoon in September 1965, when he was visiting the Jet Propulsion Laboratory in California. An astronomer had brought him data gathered by infrared-detecting instruments from the atmospheres of Mars and Venus, which revealed for the first time that they were composed principally of CO2. Lovelock realised immediately that this was evidence that both Venus and Mars were dead planets, and that Earth was different because living things had reduced its atmospheric CO2 and replaced it with oxygen. When he mentioned this to the American astrophysicist Carl Sagan, Sagan told him of the 'faint young Sun paradox', which states that, while the Sun was 25 per cent cooler three billion years ago than it is today, our planet never froze right over as it would seem it should have. Then, Lovelock says, 'the image of the Earth as a living organism able to regulate its temperature and chemistry at a comfortable steady state emerged in my mind'.[30]

The Gaia hypothesis has gained a reputation as being somewhat 'new age', as superficial popular science. However, it is anything but, being soundly based and profoundly important to our understanding of the evolution of life on Earth. In universities it is often studied as 'Earth systems science', perhaps because that sounds more respectable. Today Lovelock describes Gaia as:

A view of the Earth…as a self-regulating system made up from the totality of organisms, the surface rocks, the ocean and the atmosphere tightly coupled as an evolving system…this system [has] a goal-the regulation of surface conditions so as always to be as favourable as possible for contemporary life.[31]

When an account of the Gaia hypothesis was first published in 1972 in the journal Atmospheric Environment it gained little credibility among scientists.[32] The situation did not improve after Lovelock published his book Gaia in 1979. 'The biologists were the worst,' he recalls. 'They spoke against Gaia with the kind of dogmatic certainty I hadn't heard since Sunday School. At least the geologists offered criticisms based on their interpretation of the facts.' Some of the most important criticisms came from Richard Dawkins, who described Lovelock's book as part of 'the pop-ecology literature'.[33] The hypothesis, Dawkins believed, did not take proper account of evolution by natural selection, with its requirement for competition between organisms, writing that:

There would have to have been a set of rival Gaias, presumably on different planets. Biospheres which did not develop efficient homeostatic regulation of their planetary atmospheres tended to go extinct. The Universe would have to be full of dead planets whose homeostatic regulation systems had failed, with, dotted around, a handful of successful, well-regulated planets of which Earth is one…In addition we would have to postulate some kind of reproduction, whereby successful planets spawned copies of their life forms on new planets.[34]

These criticisms prompted Lovelock to investigate how a process based on competition could create 'the contented face of nature' and to do so he developed a computer model, in 1982, known as Daisyworld.

Daisyworld is an attempt to see what would happen on an imaginary planet with a very simple ecology that followed the same orbit around the Sun as Earth. Only daisies grow there, and they vary from dark- to light-coloured. They can grow only in a temperature range of 23° to 104° fahrenheit, with an optimum of around 68° fahrenheit. The only thing that affects the temperature of this model world is how reflective its surface is: if it's bright then more sunlight is reflected into space before it turns into heat energy; if dark, then lots of sunlight is turned into heat energy and so Daisyworld heats up. A bright daisy will thus cool its surroundings, while a dark one will warm them.

In order to investigate the 'faint young Sun paradox', Lovelock ran programs to simulate conditions as they have been throughout Earth's history. As the programs ran, large clusters of light-coloured daisies died off because their surroundings became too cool, while similar clumps of dark ones died because they became too warm. Over numerous computer generations of daisies, the proportion of light and dark types became balanced so as to keep conditions at the surface relatively constant and within the optimum temperature range for daisy growth. Over the years, more complex Daisyworld models have been developed that better mimic the natural world. But always the results are the same: life as a whole (albeit virtual life) regulates conditions to suit itself. That is, until it meets a force so great-such as an asteroid or emission of greenhouse gas-as to overwhelm its control mechanisms.

Calling Daisyworld his 'proudest scientific achievement', Lovelock argues that it completely answers the criticism that Gaia could not evolve by the process of Darwinian natural selection. It's a view championed by Mark Staley, one of the foremost proponents of Daisyworld-type modelling, who says of the models that 'the end result may appear to be the product of a cooperative venture, but it is in fact the outcome of Darwinian selection acting upon "selfish" organisms'.[35] Several real-world examples of Daisyworld-like regulation have now been discovered. Among the most intriguing is the way coral reefs increase cloudiness in the air above them through the production of cloud-seeding chemicals, thus shading themselves from dangerous ultraviolet radiation. Another example concerns rainforests like the Amazon, which transpire water vapour, generating their own rainfall.

In summary, Lovelock's Gaia hypothesis describes cooperation at the highest level-the sum of unconscious cooperation of all life that has given form to our living Earth. It's not that living things choose to cooperate, but that evolution has shaped them to do so. It also shows that the living and non-living parts of Earth are inextricably interwoven. Lovelock argues, for example, that 99 per cent of Earth's atmosphere is a creation of life (the exceptional 1 per cent being the noble gases such as Argon) and that Earth's oceans are maintained in their current state by life itself. But most importantly, the Gaia hypothesis posits that Earth, taken as a whole, possesses many of the qualities of a living thing.

It was the novelist William Golding who suggested the name Gaia for Lovelock's hypothesis. Golding then lived in the same village as Lovelock, and doubtless knew of Gaia, the Greek goddess of Earth, from his readings of the classics. Perhaps it required the author who in 1954 had written Lord of the Flies, arguably the most terrifying 'survival of the fittest' novel ever published, to provide the modern world with a name for a unified theory of life. Two decades later Golding returned to the contemplation of Gaia. In a 1976 review in the Guardian of a book of aerial photography, he opined:

Our growing knowledge both of the microscopic and the macroscopic nature of Earth is not just a satisfaction to a handful of scientists. In both directions, it is bringing about a change in sensibility…Those who think of the world as a lifeless lump would do well to watch out.[36]

The idea of Earth as a living entity is not new. In explaining the ancient Greeks' thoughts about the Earth, Sir Francis Bacon wrote in 1639 that:

The philosophie of Pythagoras…did first plant a monstrous imagination, which afterwards was, by the school of Plato and others, watered and nourished. It was, that the world was one entire perfect, living creature…This foundation being laid, they might build upon it what they would; for in a living creature, though never so great, as for example a great whale, the sense and the effects of any one part of the body instantly make a transcursion throughout the whole.[37]

Hailed as one of the founding fathers of modern science, Bacon was also a deeply religious man, and his revulsion at the Greek concept of Earth as a living thing stems in part from the church's battle with witchcraft, which was waxing hot in seventeenth-century England. If the Earth was 'one perfect, living creature', then Bacon felt that witches and sorcerers would be able to influence any part of it from a distance, just as a tweak of the toe can make an entire body jump. Their satanic works were, he feared, the deft touch to the Earth-body that might conjure storms to destroy ships at sea, or incite earthquakes to crush the cities of the righteous.

But Christian antagonism to the idea of a living Earth goes far deeper than that. After all, Gaia is a pagan god, and the early church waged a fierce battle with such competitors. It largely succeeded in imposing monotheism in western Europe, and by the eighteenth century belief in the Earth as anything like a living thing survived only in the minds of the simplest and most unschooled of peasants. In the churches and universities, in contrast, Earth was seen as a stage upon which the great moral drama of good and evil was being played out, at the end of which we would be consigned to either heaven or hell. And it was a stage over which we had been granted dominion, to treat as we liked-a view that the magnates of the industrial revolution would exploit for their own ends.

Lovelock's hypothesis is at least as controversial today as Darwin's theory of evolution was 150 years ago. Part of the reason can be found in its history of conflict with Christianity. There are still church leaders who denounce environmentalism as if it somehow competes with their version of religious dogma. Australia's leading Catholic, Cardinal George Pell, believes that environmentalists suffer from a new 'pagan emptiness'. Even worse, from Pell's perspective, they compete with religion. In January 2008 he said of climate science:

The public generally seem to have embraced even the wilder claims about man-made climate change as if they constituted a new religion. These days, for any public figure to question the basis of what amounts to a green fundamentalist faith is tantamount to heresy.[38]

And of course the deep interconnectedness central to the Gaia hypothesis presents a profound challenge to our current economic model, for it explains that there are both limits to growth, and no 'away' to throw anything to.

Within mainstream science the Gaia hypothesis long remained marginal: neither Wallace nor Lovelock ever held a university position, and there has not, until recently, been a Wallacean academic tradition. But slowly that is changing. Within geology, Earth systems science is finding some respectability, and even in the biological sciences academics are turning their attention to Gaian questions, including how the evolutionary process might have fostered cooperation. Those interested in such questions are known as sociobiologists. Oxford University's Bill Hamilton is widely seen as the discipline's founder, and Harvard's E. O. Wilson its greatest living exponent. Sociobiology is a synthetic science which seeks to explain the social behaviour of animals through evolutionary theory. Some scientists (among them Stephen Jay Gould) have aligned sociobiology with social Darwinism, but in reality it deserves to be classified with the other synthetic sciences, such as astrobiology and Earth systems science. As we explore the themes of this book we'll hear more of it, and particularly of its founder, the great Bill Hamilton, for he came as close as anyone ever has to bridging the gulf between Neo-Darwinism and the Gaia hypothesis.

CHAPTER 4

A Fresh Look at Earth

Big ball of iron with some rock on the outside and a very very thin coating of moisture and oxygen and dangerous creatures.

A DESCRIPTION OF EARTH, WIKIPEDIA

What is life? Is it separable from Earth? At the most elemental level, we living beings are not even properly things, but rather processes. A dead creature is in every respect identical to a live one, except that the electrochemical processes that motivate it have ceased. Life is a performance-heavens' performance-which is fed and held in place, and eventually extinguished, by fundamental laws of chemistry and physics. Another way of thinking about life is that we are all self-choreographed extravaganzas of electrochemical reaction, and it is in the combined impacts of those reactions, across all of life, that Gaia itself is forged.

Thinking of life as something separate from Earth is wrong. A striking instance concerns the origins of diamonds. Analysis shows that many diamonds are made from living things. Tiny organisms adrift on an ancient sea took in carbon from the atmosphere, then died and sank into the abyss. From there geological processes carried the carbon into the Earth's very mantle, subjecting it to unimaginable heat and pressure, thereby transforming it into diamonds. Eventually these were shot back to the surface in great pipes of molten rock, and today some grace our fingers.[39]

Our planet formed some 4.5 billion years ago as a result of a 'gravitational instability in a condensed galactic cloud of dust and gas'.[40] It formed in an astonishingly short time, perhaps as little as ten million years, and critically important qualities were added when a heavenly body the size of Mars struck the proto-Earth, liquefying it and ejecting from it a mass destined to become the Moon. The liquefied remainder then began to differentiate into a metallic core, making up almost 30 per cent, a silicate mantle making up almost 70 per cent, and a thin crust making up just 0.5 per cent. Within a billion years, or perhaps just a few hundred million years, parts of that crust had begun to organise into life.

That was so long ago that the Moon was far closer than it is today, and was replete with active volcanoes. It loomed large in the sky, and exerted such gravitational pull that Earth's crust buckled many metres with each tidal swing. It challenges our imagination to think of microscopic portions in that ancient crust slowly becoming living things, and indeed how the spark of life was first kindled remains one of science's great mysteries. But there is no doubt that the electrochemical processes that are life are entirely consistent with an origin in Earth's crust-our very chemistry tells us that we are, in all probability, of it. This concept of life as living Earthly crust challenges the dignity of some. It should not. We have long understood, from biblical teaching and practical experience, that we are naught but earth: ashes to ashes, dust to dust, as the English burial service puts it. Indeed, 'dust thou art, and unto dust shalt thou return' are among the oldest written words we have.[41]

The building blocks of life, however, go back even further than the formation of our planet. The elements that form us, the carbon, phosphorus, calcium and iron to name but a few, were created in the hearts of stars. And not just in one generation of stars, for it takes the energy of three stellar generations combined to form some of the heavier elements, such as carbon, that life finds indispensible. Stars age very slowly, and to complete three generations takes almost all of time-from the Big Bang to the formation of Earth. We are, as the astrophysicist Carl Sagan said, mere stardust, but what a wondrous thing that is.

Earth's crust may seem like a passive organ, a mere substrate, but it has been profoundly influenced by life, and it is the sheer size of life's energy budget (the total amount of energy living things capture from the Sun) that makes this possible. Plants capture the Sun's energy using photosynthesis. Inside green leaves lie tiny structures, called chloroplasts, which use the energy of sunlight to break apart molecules of CO2 which, if they were not so dealt with, would eventually make up most of Earth's atmosphere. Plants use the CO2 to form organic compounds, which in turn are used to build bark, wood and leaves-indeed all the tissues of the plants around us. Look at a tree and what you see is mostly congealed carbon, a tonne of dry wood being the result of the destruction, by photosynthesis, of around two tonnes of atmospheric CO2.

Green plants are far more efficient in their energy use than we humans with our fossil-fuelled power stations. Each year green plants manage to convert around one hundred billion tonnes of atmospheric carbon into living plant tissue, and in so doing they remove 8 per cent of all atmospheric CO2. This is a truly extraordinary figure. Just imagine if no CO2 found its way into the atmosphere. In just twelve years plants would then absorb and use almost all of the atmospheric CO2.

Plants capture about 4 per cent of the sunlight that falls on Earth's surface, which gives life a primary energy budget (excluding sulphur bacteria and other non-photosynthetic pathways) of approximately one hundred terawatts (one hundred trillion watts) annually. It's the size of life's primary energy budget and the resilience of its ecosystems (which is determined in part by biodiversity) that define a healthy planet. Scientists have only begun to think about Earth in these terms, so measurements of productivity and diversity remain approximate. Yet it's clear from major extinction events in the fossil record that if Earth's energy budget and ecosystem resilience fall below certain thresholds, a fully functioning Earth system cannot be maintained.

Useful parallels can be drawn between the way energy flows in economies and Earth's ecosystems. The size of economies is measured in dollars, while Earth's energy budget is measured in terawatts. Dollars and terawatts clearly differ, but both represent potential resources that can be put to productive ends. Although an area of active study and dispute, it seems that the stability of both economies and ecosystems is related to their diversity, which itself is partly a function of size: the larger an economy or an ecosystem, the more diverse it can be. The presence of certain elements in economies and ecosystems can also help foster productivity. Banking is a good example. In economies well-run and well-regulated banks aid the flow of capital, thus stimulating productivity. In ecosystems certain species act rather like bankers by facilitating energy and nutrient flows. Earth's ecological bankers include the big herbivores, those weighing a tonne or more. As we'll soon see, in marginal ecosystems such as deserts or tundra, these ecological bankers speed the flow of resources through the ecosystem, allowing a substantial 'biological economy' to be built on a slender resource base. If humans destroy megafauna, they can induce the equivalent of a never-ending recession on such ecosystems, limiting their productivity and stability. And that impacts Earth function as a whole, just as a recession in the US can affect the global economy.

So how does life spend its capacious energy budget? Basically, it is deployed to modify our planet so as to make it more habitable, and just how that is done is best understood by comparing Earth with the dead planets, such as Venus and Mars. Planets can have up to three principal 'organs', which correspond to the three phases of matter: a solid crust, a liquid (or frozen) ocean and a gaseous atmosphere. A living planet uses its energy budget to kick the chemistry of its organs out of balance with each other. No greater example of this exists than oxygen. Earth's atmosphere is full of this highly reactive element, but if life was ever extinguished oxygen would quickly vanish by combining with elements in the rocks and oceans, forming molecules such as CO2. The chemical composition of the organs of dead planets, in contrast, exists in a state of equilibrium. As Lovelock realised in the 1970s, a planet whose atmosphere consists almost entirely of CO2 is a planet whose life force, if there ever was one, is long exhausted-a planet at eternal rest.

Carbon is the indispensible building block of life. You and I are made up of 18 per cent carbon by dry weight, and plants have a much higher percentage. Almost all of that carbon was once floating in the atmosphere, joined in a ménage à trois with oxygen to form CO2. Billions of years ago, when life was a weak infant struggling to survive, there was more CO2 in the atmosphere than there is today, for living things had not yet discovered a means to use it. Back then, perhaps, life nestled as microscopic bacteria in the bosom of the deep sea, or hid in sediments around hot springs. Wherever it found a refuge, its energy budget must have been small, as most of Earth was still untouched by its power. Today, however, CO2 forms just four parts per ten thousand of the gaseous composition of Earth's atmosphere, while a by-product of photosynthesis, oxygen, forms 21 per cent. This is the ultimate measure of life's triumph.

Earth's continental crust is far thicker than its oceanic crust and it's made of lighter, silica-rich rock. The continents originated from erosion of the oceanic crust (which is made of basalt) and, remarkably, they may be a product of life. This might seem to be a large claim, but it's worth keeping in mind that living things provide 75 per cent of the energy used to transform Earth's rocks, while heat from within the Earth provides a mere 25 per cent.[42] We tend to think about the transformation of rocks in Earth's crust as the result of volcanoes, earthquakes and such like. It's easy to overlook the silent work of lichens, bacteria and plants, which create grains of soil from intransigent basalt and other rocks by reaching deep into the strata, leaching and breaking down the rock with the acids they exude. Their work, while microscopic in scale, is ceaseless, and thrice greater in effect than that of all the world's volcanoes combined.

We have no evidence of life for the first half-billion years or so of Earth's existence. Back then our planet was a water-covered sphere with little or no dry land. When life originated, those ancient living things, it has been suggested, produced acids that sped up the weathering process of the basaltic crust, separating the lighter elements in the basalt from the heavier ones. When these lighter elements are compressed and heated by movements in Earth's crust they become granite, the foundation-stone of the continents and the essence of the earth beneath our feet. Perhaps, given enough time, energy from within the Earth could have affected the same transformation, but so vast was the amount of basalt weathered to create the first continents that recent research indicates it could have occurred only if life was capturing energy and using it to produce compounds that help break down rocks.[43]

We can think of Earth's rocky crust as a huge holdfast, like the lower shell of an oyster, which life has formed to anchor itself. And if we imagine the rocks as life's holdfast, then we can think of the atmosphere as a silken cocoon, woven by life for its own protection and nourishment. Just consider what the atmosphere does for us. Its greenhouse gases keep the surface of the planet at an average of around 59° fahrenheit, rather than around -0.4° fahrenheit. All of the principal greenhouse gases are produced by life (though some, such as CO2, can be produced in other ways as well), and without them Earth would be a frozen ball. Ozone, a form of oxygen composed of three atoms bonded together, is a product of life, for all free oxygen is derived from plants. While it makes up just ten parts per million of our atmosphere, it captures 97 to 99 per cent of all ultraviolet radiation heading our way. Without this protection, our DNA and other cellular structures would soon be torn apart and life at Earth's surface would cease to exist. Then there is the more common form of oxygen (two atoms bonded together), which fuels our inner metabolic fires, providing the breath of life itself.

As Wallace knew, our atmosphere is truly wondrous. We may think of it as big, but it is by far Earth's smallest organ. To compare it with the oceans, we need to imagine compressing its gases around eight hundred times, until it becomes liquid. If we could do that, we'd see that the atmosphere is just one-five hundredth the size of the oceans. It's a delicate, dynamic and indispensible wrapping to the planet, a cocoon that is constantly being repaired and made whole by life itself, a cocoon that intimately wraps around every living thing and connects chemically with a great rocky shell that life has forged as its support. And sandwiched between holdfast and cocoon is the liquid circulatory system of the beast: Earth's oceans and other waters.

Earth is truly the water planet, for water in its three states-vapour, liquid and solid-defines and sustains it. Liquid water covers 71 per cent of Earth's surface while solid water, mostly in the form of glacial ice, covers a further 10.4 per cent. Water is essential to life because the electrochemical processes that are life can occur only within it; fluids as salty as the ancient oceans flow through our veins. The ocean was almost certainly the cradle of life, and it remains life's most expansive habitat. With a volume of 1.37 billion cubic kilometres it is eleven times greater in volume than all of the land above the sea. But unlike the land, which is populated by life only at its surface, the entire volume of the oceans is a potential habitat.[44]

At the very beginning of our planet's existence, Earth was lifeless and its three organs were in chemical equilibrium. No rocks survive from that distant time 3.9 to 4.65 billion years ago. That's because our restless planet has been continuously recycling itself, so that almost all the physical evidence testifying to the nature of Earth's original crust has been ground to dust, melted and formed anew. But by examining rocks that date to a slightly later time, when Earth's life force was still weak, we can gain deep insights into what the enlivening of our planet meant.

In 2009 I visited the man who pioneered the still controversial idea that life might have helped create the continents. Minik Rosing is the director of the Geological Museum in Copenhagen and one of the foremost authorities on the origin of life. A ponytail- and jeans-wearing Inuit, he's possessed of immense hospitality, and as we sat in his office drinking tea and watching the snow fall outside, he spoke of his love of old rocks. The most venerable surviving parts of Earth's rocky crust are, he said, between 3.3 and 3.8 billion years old. They're precious relics of the youngest Earth we can directly know, formed less than a billion years after the planet itself came into existence. And the very oldest can be found in Greenland.

Minik rose from his seat as he spoke and handed me a rock from his desk. It was, he said, around 3.8 billion years old, and I was astonished to see that it was not folded, battered and scarred as you might expect, but undistorted, its layers as smooth as sheets on a hospital bed. In one layer was a slender black smear, which Minik said marked the start of Earth's carbon cycle, a cycle that largely defines and maintains our planet. Instantly my mind was swallowed by the gulf of time that separates us from that moment when the living Earth-machine first ticked over. Today the carbon cycle runs at full roar, but back then, in a shallow ocean on a planet as fragile as an unshelled egg, it was as delicate and fluttering as a quickening.

Geologists have learned a great deal about the infancy of our Earth through studying such rocks, and no lesson is more marvellous than the strong grip that life has exerted on our planet over its 3.5-billion-year existence. At the time those rocks were formed, and for long after, Earth's atmosphere was toxic, incapable of supporting life as we know it. The oceans also were a toxic brew, with high concentrations of metals such as iron, chromium, copper, lead and zinc, as well as carbon and other elements. All of this changed when microscopic plants and bacteria began to break CO2 into oxygen and carbon, and to use the metals dissolved in the sea water to speed up the chemical reactions that were essential to their existence. As they died and sank to the ocean floor, they carried their minute cargoes of metals with them, and so, over aeons, the oceans were purged of their dissolved metals, becoming chemically similar to the oceans of today. The metals buried in the sediments had a different fate. Often, they were carried deep into the crust, where heating and compression further concentrated them, leading to the formation of ore deposits. Sometimes these ore bodies became incorporated into the continents and were thrust high into mountain ranges, forming the fabulous golden wealth of places like Telluride, Nevada, or the Incan mines of Peru. A similar process gave rise to Earth's coal, oil and gas deposits, though these formed as a result of living things pulling CO2 from the atmosphere, rather than from them taking metals into their bodies.

This distant Earth history has profound implications for our modern industrial society. It accounts not only for the state of our atmosphere and oceans, and the good fortune of some countries in possessing valuable mineral deposits, but for our bodies' often-calamitous love of toxic metals as well. All of that matters because today we are digging up these elements at an unprecedented rate, and redistributing them through our air and waters, and that can have surprising consequences. As we will learn later, this is a tale of fundamental planetary disorder, which helps explain why some of us develop disorders such as intellectual disabilities and schizophrenia, and even perhaps why murder rates are high in some communities.

It may seem a paradox that living things should take in toxic metals such as cadmium and lead as avidly as if they were the most precious nutrients on Earth. Assay any one of us and you'll find a treasure trove of toxic metals at concentrations many times greater than they occur in the natural world around us. The answer to the paradox lies in those oceans of long ago. Back then life consisted of little more than bags of chemical reactions floating in an ocean packed with metals. The laws of chemistry dictate that some of the reactions most crucial to life are enhanced by the presence of metals. In technical parlance, metals are catalysts and co-factors-substances that either permit or accelerate chemical reactions. Catalysts are perhaps most familiar to us from the catalytic converters in cars, which work by using a metal, often platinum, to hasten reactions that remove pollutants from the car's exhaust. In our bodies catalysts hasten enzymic reactions and, in an ocean full of potential catalysts, early life became dependent upon them. So unchanging has life's chemistry been over the past two billion years that the majority of the seven hundred-odd chemical reactions that run our bodies today are identical to those that occurred in those bags of chemical reactions that were early life.

As early life mined the ocean's dissolved metals the waters became leached of catalysts and living creatures became desperately hungry for them. Even today, it is metals that limit life's spread in the oceans. In the frigid Southern Ocean, for example, a lack of iron is the key factor limiting plankton growth. Add iron and life flourishes. After two billion years of coping in a world where metals are not easy to be had, life has become extremely adept at keeping hold of whatever metals come its way. And in a world where human activity is releasing metals to the air and seas in ever greater abundance, that can be dangerous, for, like many good things, too much metallic catalyst can be very dangerous. So it is that, despite the damage mercury does to us, our bodies absorb the mercury in the fish we eat even more avidly than the flesh of the fish itself. We store up the metal in our livers, skins and brains, even after we are mortally poisoned by it.

The links between Earth's oceans, crust and atmosphere are nowhere more elegantly exhibited than in the theory of continental drift. Every three hundred million years or so the continents coalesce, creating a single large continent surrounded by oceanic crust. Then the landmass breaks apart again, eventually to come together in another cycle. You can think of the continents acting like dollops of scum floating on a pot of boiling water. The dollops move around, joining together and breaking apart, driven by the convection in the boiling water. While no one understands precisely what drives the movements of the continents, convection within Earth's molten mantle, Earth's gravity, and the pull of the Moon all appear to be factors.

There are two kinds of plates: continental and oceanic. When two continental plates are moving apart, new oceanic crust forms between them. When a continental and oceanic plate collide, however, the oceanic plate is thrust under the continent, and is melted. As a result, mountain ranges, volcanoes and mineral-rich rocks are formed. A good example of this is the Andes. When two continental plates collide, it's far harder for one to slip under the other. Instead the plates buckle, and truly gigantic mountains, such as the Himalayas, are formed. Rivers erode the mountains, creating fresh new soil, and it's this renewal, along with the slow grinding of glaciers, that fertilises life on Earth with the minerals that are essential to plant and animal growth. It's no accident that some of our greatest civilisations sprang up on the plains laid down along rivers flowing from high mountains. If the continents were spawned by life, then we must see this fantastic movement of Earth's plates as at least partly a consequence of life itself.

The most important thing about the movement of the continents in relation to life in the oceans is the effect it has on the recycling of salts. The waters of the ocean are recycled, by evaporation and precipitation and thence through Earth's rivers, every thirty to forty thousand years, and with each recycling rivers leach salt from the continental rocks and carry it into the sea. You might deduce from this that the oceans are growing saltier, and in the nineteenth century this is exactly what scientists thought. They assumed that the oceans contained fresh water upon their formation, and, knowing the rate at which salt is carried into the oceans by rivers, they estimated Earth to be just a few tens of millions of years old. They then coupled this faulty finding with a prediction that a sort of salty doomsday awaited us a few million years hence, when the oceans would become as salty as the Dead Sea.

The truth is far more remarkable. The saltiness of the oceans has remained relatively constant for billions of years, and the drift of the continents plays a vital role in this regulation. As the continents move apart, the ocean's basalt crust is stretched ever more thinly, until it finally ruptures. These rupture lines are known as mid-ocean ridges. They are often located near the centre of ocean basins, and they allow the basins to grow wider. These remote, submarine mountain ranges are rich in life but are among the least known places on Earth. Greg Rouse, a friend of mine, explores them in a submersible, and he's one of the few humans ever to have seen them at first hand.

In 2005 Rouse explored one of the last unknown submarine mountain ranges, deep in the South Pacific Ocean. He showed me video footage taken on the trip of a fantastical white octopus which he had captured using a robotic arm and put in a container on the outside of the submersible. He was wildly excited at the thought of naming and describing the amazing creature, but during the three-hour ascent the ghostly octopus managed to open the lid of its container and escape back to the depths. He also told me something completely surprising. On the evening before one dive, a filleted fish had been cast overboard by a crew member of the support vessel, and when Rouse arrived at the crest of the range four kilometres below, he discovered the filleted fish lying on the bottom, just where the submersible landed. For this to occur, the column of water below the vessel must have been completely serene. To us inhabitants of the turbulent atmosphere such things are utterly astonishing, and they underline how little we understand our planet and its workings.

Mid-ocean ridges form where two continents are moving apart, stetching the oceanic crust between them. They resemble a double-crested mountain range, and between the crests, in a sort of rift valley, molten rock from deep in the Earth's crust comes to the surface. Hydrothermal vents-deep, fluid-filled cracks in the oceanic crust-form, and all of the ocean water in the world eventually circulates through these. It takes between ten million and one hundred million years for all the water to be recycled through the hydrothermal vents, but as it circulates the chemical structure of the sea water is altered by the extreme heat, and the salt is removed. This recycling of the oceans through evaporation, rainfall and rivers every thirty to forty thousand years, and through the crust at the mid-ocean ridges every ten million years or so, keeps the saltiness of the sea constant. And none of it would be possible without continental drift.

What this potted history of Earth tells us is that if we wish to keep our planet fit for life, some of the most routine and humble things we do must change. For as long as we've existed our conception of waste disposal has simply been shifting objectionable matter from one of Earth's organs to another. Whether it's been a human body or a banana skin, we've buried it (returning it to the earth), burned it (returning it to the atmosphere) or tossed it into the sea. On a small scale, this approach to waste disposal works pretty well. But it most decidedly will not do in the twenty-first century, for the very essence of much pollution derives from human actions that weaken the elemental imbalance between Earth's organs. Over the vastness of geological time Gaia's housekeeping has put every element in its place. Carbon has been withdrawn from the atmosphere by plants and geological processes, until just a few parts per ten thousand remain. Iron has been stripped by hungry plankton from the seas, as have mercury, lead, zinc, uranium and a great many other elements, all of which have been safely sequestered deep in Earth's rocks. But now the human burrowers in the Earth have arrived, and, as we tunnel into those buried troves, we undo the work of aeons.

CHAPTER 5

The Commonwealth of Virtue

So long as a country remains physically unchanged, the numbers of its animal population cannot materially increase.

ALFRED RUSSEL WALLACE 1858

For four and a half billion years our Earth has waltzed around the Sun, and in its silent progress it has given birth to life-at first simple and uncoordinated, but today breathtakingly complex. Life uses Earth's crust as a kind of great rocky shell-a skeleton which it helped to create and to which it is irrevocably and intimately anchored. This shell permits the recycling of elements that are essential to the continued presence of life, and also acts as a vault for locking away toxic compounds. The oceans and other waters are life's bloodstream, helping convey nutrients, heat and elements through the whole, while that most amazing creation of life, the atmosphere, protects, recycles, conveys and clothes. And, ensconced on such a planet, life has ramified and interconnected at every level: from the simple ecology of a bacterial community, to an ant colony, to a bird and so on to the planet itself. But the degree of integration between the numerous and complex parts of these living confederations varies-from loosely organised ecosystems to the intricate integration of an organism such as a human being.

Is Gaia like a human body, an ant colony, an ecosystem-or something else? The physician Lewis Thomas, when investigating this question, wrote of our world, 'We do not have solitary isolated creatures.'[45] Every creature is, in some sense, connected to and dependent upon the rest. 'One way to put it is that the Earth is a loosely formed, spherical organism, with all its working parts linked in symbiosis.'[46] Influenced by Earth's spherical shape, Thomas felt that the closest analogy to Gaia was a single cell. But the most vital words in his lucid description are surely 'loosely formed'. It is the degree of interconnectedness that differentiates ecosystems, insect colonies and organisms. Cells are hardly loosely formed, but it's worth remembering that even the most tightly interconnected organisms evolved from miniature ecosystems. Recall the angophora tree, with its chloroplasts that were once bacteria. The cells of our bodies provide another excellent example. They are composed of two or more entirely separate and unrelated types of creatures which must once have been relatively independent parts of an ecosystem on a young Earth. The bacterial partner is known as mitochondria, and it's what gives cells energy. These partners must have started by forming a loose association, but after more than a billion years of evolution they have become the indivisible parts of an organism, or rather every organism on the planet. Every multicellular being is descended from such a union.

There are clues in today's living world of how this remarkable partnership may have started. Corals are polyps that resemble miniature sea anemones. By themselves they are colourless. All the colours we see in coral reefs come from tiny algae that live inside the coral polyps' cells. These algae benefit the coral by helping feed it, and they in turn gain shelter. While the relationship is intricate, it is not indissoluble-the coral polyp can temporarily expel the algae if it suits it. Left without algae for too long, however, the coral polyp starves and coral bleaching is the result. The difference between this relationship and that between the cells of our body is that the once free-living bacteria that are our mitochondria have been with our cells for so long that neither can survive-even for an instant-without the other.

The complexity of relationships doesn't stop there. Larger living thing are themselves composites, involving whole ecosystems of bacteria, fungi and invertebrates. Without many of these creatures-our gut bacteria, for example-we could not exist. These fellow travellers make up 10 per cent of our weight, and are so pervasively distributed over our bodies that were we to take away all 'human' cells, a detailed body-shadow composed of them would remain: we are in ourselves virtual planets of Gaian complexity.

Time is important in forging such interdependence, and Gaia is very old-a quarter as old as time itself. But has Gaia, over that near-eternity, established the kind of interdependence characteristic of an organism? Profound organisational rules guide the development of cooperation, and as our bodies have grown more complex the specialised cells that form our brain and nerves have created command-and-control systems. Such systems, even if they are not created by nerves and brains, are the hallmark of the organism, being present in all but the most rudimentary of multicellular animals.

Entities such as ant colonies lack command-and-control systems, but they do have means of coordinating their activities. It's astonishing to consider that the intricate workings of an ant colony, with its millions of individuals and hundreds of metres of interconnected tunnels, is maintained without command and control. But such is the case, for there is no brain caste or blueprint for the colony resident in any individual ant brain. Instead, the activities of the ants are regulated via chemicals, known as pheromones, which they create and disperse. These chemicals elicit a specific response from an ant, so if one comes across a particular pheromone, say on an ant trail, it will behave in a certain way. While rudimentary by comparison with the functioning of a nervous system, these chemicals allow sufficient coordination for colonies of millions of individuals to function.

Gaia clearly lacks a command-and-control system, but perhaps it possesses something roughly equivalent to pheromones. These are substances, created by life, which can act to maintain conditions on Earth favourable to life. Among the most important are ozone, which shields life from ultraviolet radiation, and the greenhouse gases CO2, methane and nitrous oxide, which play a critical role in controlling Earth's surface temperature. Dimethyl sulphide is another. It is produced by certain types of algae, and it assists in cloud formation. Clouds play a vital role in the Earth system by bringing rainfall, shading vulnerable organisms and altering Earth's brightness (its albedo). Atmospheric dust, much of which is organic in origin, or derived from rocks through weathering processes, may also have a regulatory effect.

Clearly these substances differ from pheromones in that they do not elicit responses from other individuals, but from the Earth system as a whole, and they are often multiplicitous in their impact. But they do have a pheromone-like effect, in that they contribute to the maintenance and good running of the entity. And like pheromones they are potent-even minute traces can generate a powerful response. For these reasons I think it appropriate to refer to these substances as 'geo-pheromones'.

One of the foundation stones of Lovelock's Gaia hypothesis is the idea that Earth regulates its surface temperature to favour life. But how well does it do it? Self-regulation (or homeostasis) gives some indication of how integrated an entity is. Warm-blooded (homeothermic) organisms such as ourselves maintain a constant body temperature regardless of external conditions. And some of the most complex ant and termite colonies manage to do the same thing, the colony's internal temperature being controlled by a sophisticated architecture that rivals that of skyscrapers. Is Gaia similarly competent?

Lovelock's first indication that Earth could regulate its surface temperature came from the 'faint young Sun' paradox, which states that although the Sun was 25 per cent cooler three billion years ago than it is today, the average surface temperature of the Earth has stayed within a narrow range. This seems a convincing argument for efficient self-regulation, but on shorter time scales Earth's average surface temperature varies enormously, the shift from ice age to interglacial conditions (such as we are now living in) being a fine example. Every hundred thousand years for the past million years, Earth has experienced a cycle of gradual freezing followed by abrupt thawing, which involves a rapid increase in average temperature of around 9° fahrenheit-from around 48° to 57° fahrenheit. This huge increase occurs within around five thousand years, and is driven by small changes in Earth's orbit, its tilt on its axis and its 'wobble' on its axis which occur in cycles known as the Milankovitch cycles, after their discoverer the Serbian engineer Milutin Milankovitch. Their impact on the amount of energy Earth receives from the Sun is small-just 0.1 per cent-though where the sunlight falls varies more. The Arctic receives more summer sunlight during that part of the cycle where Earth's tilt is greatest and the Arctic is nearest the Sun. But such large changes resulting from minute variations suggest, initially at least, that Gaia's ability to control its temperature is inferior to that of the most highly evolved superorganisms.

James Lovelock, however, has a different explanation. He points out that Gaia is composed of two parts, each with different requirements, and that the huge temperature shifts which occur as glacial periods gives way to interglacials result from one of these entities gaining supremacy over the other. The two entities Lovelock refers to are life in the sea and life on land. Life on land prefers an average temperature of around 73.4° fahrenheit, for that's the temperature at which land-based plants flourish. Life in the oceans, in contrast, prefers a more chilly 50° fahrenheit or less: at such temperatures the ocean's surface and bottom waters can mix through convection, bringing nutrients to the surface. If Lovelock is correct, then our Earth has a two-state thermostat, which results from a colossal tug of war between life on land and in the sea, each pulling Earth's temperature towards its preferred state, the balance of power being altered by the tiny variations brought about by the Milankovitch cycles. This might not seem to reflect the condition of most organisms and superorganisms such as ant colonies. But consider the reptiles, or even hibernating mammals. They also exist in one of two states, warm or cold, depending upon external conditions.

The founder of sociobiology, Oxford University's Bill Hamilton, was one of the greatest biologists who ever lived. After a lifetime studying colony-forming insects such as ants and bees, in his fifties he turned his mind to the nature of Gaia, and he did so in an intriguing way-by considering the role that life might have in contributing to atmospheric convection. With his co-author Tim Lenton, he wrote that:

Herrings falling with rain miles inland in Scotland, frogs and a juvenile turtle being found in American hailstones, and live bacteria and fungal spores collected by rocket more than 50 km from the Earth's surface all demonstrate that both terrestrial and marine organisms are sometimes raised very high by extreme atmospheric events.[47]

But what causes such vigorous circulation? Hamilton and Lenton concluded that plankton and bacteria, emerging from the ocean's surface as bubbles burst, contribute to cloud formation by becoming nuclei for water droplets. In effect they had discovered some of Earth's more important geo-pheromones. But they also believed that they'd discovered the reason that these microscopic organisms have evolved properties that enable them to behave this way. In brief, Hamilton and Lenton argued that Earth's convection is assisted by plankton and bacteria because a vigorous convection helps them disperse, thus giving them a truly global reach. We can imagine the bacteria and plankton being carried high into the atmosphere, then falling over Earth's entire surface reaching every suitable habitat available to them. The concept neatly synthesises Darwin's and Wallace's thoughts on dust, though neither man is referred to in Hamilton and Lenton's paper. But Hamilton and Lenton go further than Darwin or Wallace, speculating that the various kinds of plankton might work as teams, some species helping to produce winds, and others ice nuclei, which drop the tiny travellers back to the surface. In summarising their work, they said:

The mechanisms we describe do not directly bring us any nearer to discovering why life influences that are stabilising to the planet should be more common than destabilising ones…But a proof that large side effects, stabilising or not, can arise from activities that are adaptive…for thoughtless aerial and marine plankton, strengthening the expectation of large influences from similar unpromising systems, can perhaps help clear a path towards a principled theory.[48]

That principled theory, which might have explained Gaia, may well have been discovered by Hamilton had his research not taken a fatal turn. Shortly before his death he wrote to Lenton that he was excited about a computer program that seemed to show that as ecosystems become more complex they also become more stable and productive. As he put it:

A Genghis Khan species may be less likely to be about to destroy life on the planet than I had previously speculated…Even with an 'unexpandable resource base' to the model we do find some accumulation of resistance to disaster from the next species added; and when the model is endowed from the first with physical possibility that its resource base can be expanded if the right species are acquired, very disturbance-resistant communities sometimes appear.[49]

Such stability, of course, is the very essence of Gaia theory, and to find it in a computer model more complex than Daisyworld (which did not impress Hamilton) seemed a major step forwards.

Then, in the 1990s, Hamilton became obsessed with an idea worthy of Wallace himself-that the origin of HIV lay in oral vaccines given to children in the 1950s-and it led him to Africa in search of proof. While in the Democratic Republic of Congo he contracted malaria and was evacuated to Britain. Just six weeks later, on 7 March 2000, he died of cerebral haemorrhage. Ever the entomologist, he left a sum in his will for:

My body to be carried to Brazil…It will be laid out in a manner secure against the possums and the vultures…and this great Coprophanaeus beetle will bury me. They will enter, will bury, will live on my flesh; and in the shape of their children and mine, I will escape death. No worm for me nor sordid fly, I will buzz in the dusk like a huge bumble bee. I will be many, buzz even as a swarm of motorbikes, be borne, body by flying body out into the Brazilian wilderness beneath the stars, lofted under those beautiful and un-fused elytra which we will all hold over our backs. So finally I too will shine like a violet ground beetle under a stone.[50]

Had Hamilton lived to combine the 'narrow roads of gene land', as he characterised his genetic research, with the expansive vision of Wallace and Lovelock, he may have become the most revered biologist of all time.

In his absence we continue to struggle with the question of whether Gaia is akin, in its level of organisation, to an organism, an ant colony or an ecosystem. It seems to me that the level of organisation that can be achieved using geo-pheromones is perhaps best described as a 'commonwealth of virtue'. In such a commonwealth the various elements are sorted and stored in the most appropriate planetary organ. Non-living parts of the system are coopted for the benefit of life, and there is no 'waste' because species recycle the by-products of others. And there is a tendency, over time, towards increased productivity and interdependence. All of this is achieved in the absence of a command-and-control system, and with only limited ability to elicit specific, system-wide responses. The remaining question, as Hamilton realised, and which we shall re-visit towards the end of this book, is whether a commonwealth of virtue so defined promotes its own stability: in other words, is it Medean or Gaian in nature?

A commonwealth of virtue as I've defined it is also pretty much what an ecosystem is, although the complexity of ecosystems varies enormously. So how are ecosystems formed, and what binds them into coherent entities? Many of Alfred Russel Wallace's seemingly off-the-cuff observations led to deep thought. In the brief essay in which he introduced his ideas on evolution, he speculated on the nature of evolutionary processes in a country that remains physically unchanged.[51] It's an intriguing idea-just letting heavens' performance run on and on, without the interruptions and extinctions brought about by a restless Earth or colliding asteroids.

When we think of the evolutionary process, we most often imagine organisms evolving in response to changing conditions. Our own human lineage provides a good example, its evolutionary history having been shaped by a drying climate in East Africa. But a drying climate is just one of many possible physical changes that can shape the evolutionary process. Movements in the Earth's crust or changes in sea level can separate islands from continents, so segregating populations of animals and plants, and exposing them to different environmental pressures. Flightless birds such as the dodo, which were once found on islands round the world, are just one example of a response to such changes. Left without predators on their island homes, those individuals that put more effort into reproducing, and less into flying, are successful.

And of course the reverse can occur. Land bridges can open, allowing a mixing of species that had evolved separately for many millions of years. Such changes usually result in extinctions, as superior predators and competitors displace less well adapted ones. Extinctions also result when large asteroids strike the Earth, and here there are no immediate winners, but, as the destruction of the dinosaurs shows, species evolve to take advantage of the ecological niches vacated by the asteroid's victims. None of these events, however, would occur in a country long unchanged, which doesn't mean that evolution stops-only that different pressures drive the process. And over time they forge the intricate relationships that lie at the heart of Gaia.

It's axiomatic that the selective forces operating in a country long unchanged come from other organisms-there is no other source of challenge to drive selection. From viruses to potential mates, other living things have an impact upon the reproductive potential of an individual, and so drive the process of evolution by natural selection. Among the most important of these pressures is that exerted by members of the opposite sex. Known as sexual selection, it's a subject that fascinated Darwin. Sexual selection results from members of one sex finding certain individuals of the opposite sex more attractive than others. The peacock offers a fine example. Females are attracted to males with colourful plumage and 'eye patterns' on their tail feathers. Males with the longest, most colourful and 'eye-filled' tails leave the most offspring, resulting in today's peacocks, with their spectacular colours and cumbersome tails.

As is evident from this example, sexual selection can result in individuals that bear handicaps (the male peacock's tail hinders it as it moves about). But unless counteracting selective pressures, such as predation, are sufficiently strong, sexual selection will continue its work, often producing seemingly disadvantageous traits.

Humans offer an interesting example of sexual selection. In many traditional societies men go to considerable lengths to control the sexual and therefore the reproductive potential of women, including enforcing celibacy until marriage, dire penalties for adultery and even surgical procedures such as clitoridectomy. While such attempts can never have been entirely successful, there's no doubt that historically they have limited the mate choices available to women. Within the last few decades in western societies, however, women have, by and large, gained control of their reproduction. Liberated and armed with contraceptives, they now represent a powerful evolutionary force that is busy shaping the men of tomorrow. That's because, through the men they choose to father their children, women are manifesting in flesh the ideal mate (or as close as they can attain to it) that exists in their minds. Over evolutionary time this selection must and will change the nature of men.

Another driver of evolution in a country long unchanged results simply from the different rates at which species evolve. The last survivors of many evolutionary lineages are giants-the horses, rhinoceros and apes (including ourselves) are good examples. In the past, these lineages consisted of both small and large species, so why are they now limited to just a few giants? Small organisms reproduce more rapidly than large ones, which allows selective pressures to be exerted on a larger number of generations over a period of time. Thus, all else being equal, smaller organisms evolve faster than large ones. Where the ecological niches of smaller and larger organisms overlap, this advantage allows the smaller organisms to displace their larger, slower breeding competitors. Over evolutionary time they increase their own body sizes, and expand their ecological niche to overlap with ever larger competitors. Eventually, they replace all but the very largest members of the slower-breeding lineage. In the case of the horses and rhinos it was the cud-chewing grazers such as cattle and sheep that displaced their smaller relatives, while for the apes it was the Old World monkeys.

Natural selection that is triggered by interactions between related things is called coevolution. It can act at every level, from that of individual amino acids to entire organisms, and it may not be just a property of life, but something far more profound. Astronomers argue that black holes and galaxies develop an interdependence that's akin to biological coevolution. Indeed Erich Jantsch, in his book The Self-Organizing Universe, attributes the development of the cosmos to coevolutionary forces.[52]

Coevolution was what Bill Hamilton was investigating using computer models just prior to his death. In the real world, it can lead to the development of ever more intricate relationships, which can, in some circumstances, create a sum of biological productivity that is greater than its parts. Take, for example, the microrrhizal fungi that sheath the rootlets of the scribbly gum. Similar fungi partner with many kinds of plants that grow in poor soils, and together, even where soils are appallingly infertile, fungi and plants can create spectacular biodiversity. Indeed, the biodiversity of Africa's fynbos and Western Australia's heathlands rivals that of the rainforests. Likewise, it's the partnership between the coral polyp and its algal partner that creates the diversity of a coral reef. At a more humble level, pastoralists have always known that you can feed more cattle per hectare by sowing the seeds of half-a-dozen species of grasses rather than just one. Importantly for our future, coevolution tells us that nature's bounty is not inflexible, but is instead a kind of magic pudding that can be made to expand if cooperation between species is fostered.

In a country physically long unchanged, coevolution can produce complex ecosystems that seem to have reached an equilibrium, having altered very little in their overall structure for long periods. This is precisely what we see in the tropical rainforests of places like South-East Asia. They're filled with species, the Sumatran rhino among them, whose near relatives are found in European fossil deposits tens of millions of years old. Europe has changed greatly in that time, but South-East Asian rainforests hardly at all. It's not surprising, therefore, that it's in the rainforests, with their immensely long histories, that we find the most intricate examples of coevolution, such as the orchids and their insect pollinators.

These relationships can be extraordinarily specific. Some orchids, for example, fool wasps into attempting to mate with the stamen, and so carry pollen on specific parts of their bodies to other flowers of the same species. This phenomenon so fascinated Darwin that he wrote a monograph about it, which included a remarkable deduction.[53] He was aware of a brilliant white orchid flower from the island of Madagascar, which had protruding from it a long, spine-like nectary. Knowing that some insect would have to reach the nectar at the bottom of this structure to reap its reward for fertilising the flower, Darwin deduced that a moth with a proboscis twenty-five centimetres long existed on the island. Forty years later, long after the great man had died, the moth was discovered.

Coevolution can also lead to a kind of arms race, in which species adapt to advances made by others. On the African savannah, lions catch only the old or weak. Antelopes in their prime keep just ahead of the lions. After all, if the lions could catch those in their prime with little effort, their prey would become extinct, while if the antelopes invested energy in running far faster than lions, they'd be wasting effort. It was in such a coevolutionary world that our lineage spent at least seven million years-that's how long there have been upright apes in Africa. And all the while we've been coevolving with other African creatures-predators, prey and diseases. Coevolution explains why Africa alone among the continents retains its full diversity of large mammals. They have got to know us as predators, and as part of an evolutionary arms race they've evolved means to avoid us, which is very different from what has happened on other continents.

An astonishing example of coevolution developed in our African homeland. The greater African honeyguide, an undistinguished-looking bird of medium size, feeds solely on the larvae, wax and honey of beehives. It often attacks the hives in the evening, when a drop in temperature makes the bees lethargic, or after some larger creature such as a honey badger has damaged a hive, but when a honeyguide encounters a human, it sees an opportunity. Uttering a striking call, which it otherwise uses only in aggressive encounters with other honeyguides, it attracts the human's attention, then moves off, stopping frequently to ensure that the person is following it, all the while fanning its tail to display white spots that we visually oriented humans find easy to see. When native Africans reach a hive with the help of a honeyguide, they break it open and often thank the bird with a gift of honey.

After hundreds of thousands of years this unique relationship is beginning to break down, for in many areas sugar is becoming cheap and widespread, and people are less willing to exert themselves in the pursuit of honey. Faced with lazy humans, it seems, the honeyguide is giving up on its coevolved partners in the hunt.

I believe that coevolution, in both a biological and a cultural sense, is critical to our hopes for sustainability. Indeed, I think that our environmental problems ultimately stem from having escaped coevolution's grip, for we humans have a gypsy history, and as we've spread across the globe we've broken free of environmental constraint and destroyed many coevolutionary bonds that lie at the heart of productive ecosystems.