No one was quite sure what killed Bill Hamilton in March 2000, but it was widely supposed that he had died of malaria, contracted on an expedition to sample chimpanzee faeces in the Congo. What everyone knew for certain was that with his passing had gone the greatest evolutionary thinker of the late 20th century. Richard Dawkins certainly thought so. In a moving and delicate eulogy, he said that meeting Hamilton was the closest a modern biologist could come to meeting Darwin.
In his famous book The Selfish Gene, first published in 1976, Dawkins had produced a thrilling synthesis of the three key 20th century developments in Darwinian thought: genetics, ethology (the study of animal behaviour) and game theory. But the most original aspect of the book derived from the work of Hamilton. It explained how ruthless competition between genes could produce selfless co-operation in the organisms that carry them. "Biological altruism" is the quality which explains why bees sting in defence of their hives, even though it kills them to do so. This puzzled the young Hamilton, as it had puzzled Darwin. Bees that kill themselves must leave fewer descendants than those which hang back, so if a tendency to self-sacrifice is inherited, it would surely vanish in competition with tendencies to more selfish behaviour. But this kind of co-operation has not vanished. On the contrary, in some species, it has increased. So, over countless generations, the more altruistic bees must have outcompeted the selfish ones, something that seems to entail a contradiction in Darwinian logic. The central insight of selfish gene theory dissolves this apparent contradiction: it holds that altruistic behaviour of this sort will spread and increase if it benefits relatives of the altruist, who are also likely to carry the altruistic gene and thus to leave descendants who will in turn sacrifice themselves for their relatives, and so on. The gene for altruistic behaviour in bees competes for survival with a gene for more selfish behaviour. The result of this "strategic" competition between bee genes can be co-operation among bees. As a graduate student, working in obscurity, Hamilton had formulated and made mathematically rigorous this idea of "inclusive fitness." In some ways, it resembled Adam Smith's invisible hand, but Hamilton's formula was more precisely defined than the economic version.
The central insight was older than Hamilton, but he came upon it independently and was the first person to do the maths which showed exactly when and how genes spread in this way. When his first papers on the subject were published, in 1963 and 1964, they were barely noticed. Even today, few people have read the originals or fought through the dense thickets of equations they contain; but their central ideas are now commonplace. Having worked out the mathematics of selfish genery, he was also the first person to suggest that in order to understand the world better, we look at it from a gene's perspective. This was a thought experiment as audacious and almost as important as Einstein's wondering what light would look like if you were moving at the speed of light.
These feats alone would have secured his immortality, but he went on to work on almost every other interesting problem of recent biology. He was interested in the origins of ageing: why do we grow old when it would surely be to the advantage of our genes for us to live as long as possible? He found reasons to suggest that genes for senescence may be selected for, if they lead to advantages earlier in life, when we are reproducing. He was also one of the first people to bring game theory and evolution together. And his later work pioneered the use of computer simulations in mathematical biology. He helped to solve the puzzle of why animals cluster together into flocks or shoals, although this makes them easier for the hunters to find. (It is to do with the fact that the benefit of being on the inside accrues to more animals than are endangered on the outside.)
The last 20 years of his life were spent trying to solve a single problem. Why do genes get involved in sex? It was self-evident to Hamilton why we (and other animals) get involved in sex: because it must be good for our genes. But why? What's in it for the genes, when they could be making clones instead? An animal that makes clones of itself passes on all its genes to the next generation. But in sexual organisms, half of our genes come from one parent and half from the other. So half of the parental genes do not make it to the next generation at all. This is a puzzle. Why have sexual species not been replaced by clonal ones? Hamilton spent the latter half of his life on this problem-we'll come to his solution later-but in 1996 he displayed an unsuspected side to his talent by republishing all his early papers along with prefaces describing how they were written. It formed the first volume of Narrow Roads of Gene Land-one of the oddest scientific autobiographies ever written.
The writing was passionate, vivid, and informed by very wide reading: he quoted authors from Sophocles to AE Housman without strain or affectation. Reading it, you feel that you know him, and that he is a profoundly loveable man. He certainly was profoundly loved, as became apparent when he died, in the tributes from Englishmen generally given to emotional reserve: "He was kind, and humble, and gentle, and I loved him," said Richard Dawkins.
Yet there were signs, even in this first volume, that Hamilton did not much care for the human race. He described his loneliness as a poor graduate student in London, battling against the discouragement of his supervisor, who believed it was a waste of time to look for genetic roots to altruism. He walked around London, not only to save money: "I wanted to conjure up and recreate somehow, below the bricks and mortar around me, the marshy fields that had once been there, the streams dividing them, and the heaths beyond-to seek elemental forces underlying the city. Even a lonely child crying on the street did not tug my heart as hard as a bracken fern when I saw it, for example, in the valley of the stream once called the Fleet-a plant etiolated and pale, standing up from the deep wells of basement windows, its fronds reaching to the level of the street."
At times he would work on benches in train stations, or in Kew Gardens, just to escape the solitude of his bedsit. Yet it is difficult to avoid the conclusion that the force that drove him to the outskirts of society was not humility, but something more like the pride of Lucifer: he would rather have reigned in a bedsit than serve, unnoticed, at the LSE. (His unfashionable interest in the role of genes in the behaviour of animal populations took him to the LSE demography department after graduating from Cambridge with only a moderate upper second in genetics.)
Most of his friends thought him a humble man because he ignored the small change of everyday life. He cycled everywhere, at high speed; that's how the first grant cheque intended to establish his work in Oxford flew out of the carrier basket of his bicycle. He was a quiet man in company; quiet even when he was lecturing-he tended to face the blackboard and mutter at his equations. He himself described his attitude to society as "approaching autism."
At the end of the first volume of his memoirs, he recounts his changing attitude to the world in the 1970s, as his ideas became accepted: "For some time this solitary bear-like animal [himself] had been feeling a wind of change, a degree of acceptance, less need to shrink from the shadows either of himself or of future companions... I drew in a little my savage muzzle, sloughed some winter fur; shortly as I took another path I began to imagine my-self human."
This is entirely of a piece with Hamilton's ideas of what males are for: they are doomed to compete, and whatever the cause of sex may turn out to be, its rationale is that it cleans the gene pool by filtering out useless babies early, and a little later removing the sub-standard males who do not reproduce. Since success in reproduction is closely tied to status, and status is the product of competition between males, the low-status male really would be better off dead, with his genes trying their luck in the company of relatives' bodies.
Like most men driven enough to achieve something great, he believed that death was preferable to failure: "I strongly reject the idea that parents should welcome ill-health in their offspring because the handicapped child's achievements, great or small, should somehow elevate the spirits, the humanity, and what not, in all concerned. In fact this view illustrates quite well what I meant about natural selection being less cruel than many moralists are."
He married in 1967 and had three daughters. During the 1970s he became, by his standards, solvent. By the mid-1980s, his early ideas had become the orthodoxy of a new Darwinian faith that was sweeping all before it. They were recognised as putting biology onto a sounder theoretical footing. When he returned to Oxford from the University of Michigan in Ann Arbor in 1984, it was to a professorship set up on the recommendation of the scientist, Lionel Penrose, who had spurned him in his youth.
Success did not mellow him much. His ideas maintained their spiky and disturbing quality. In part this was because of his remorseless concentration on the theme of natural selection. Everything in nature, he believed, could be explained as the outcome of competition between genes, down to such details as the colour of leaves in autumn. To read his writing about life on earth is to wander in a Martian landscape, where the rocks have been carved by strange winds. But by the end of his life, this strangeness was taken to certify his genius. Biologists cannot win Nobel prizes unless the rules are bent, but Hamilton had won all the most glittering prizes that a biologist can. His professorship at Oxford was arranged so that he only had to give one undergraduate lecture a year. Often he forgot even that.
But where most scientists, as they grow older, grow more conventional, Hamilton never lost his interest in theories on the edge of respectability. He put a value on oddness and intellectual solitude for its own sake. He had a fondness for the Aquatic Ape hypothesis: he believed that if humanity had spent a crucial period evolving along the sea shore, this would have made us more altruistic than we became on a broad savannah, by ensuring that neighbouring tribes were more closely related to each other. He took seriously the Gaia hypothesis, which seems to have embarrassed most of the Oxford zoologists who revered his teachings. Most controversially, he became convinced by the theory, elaborated by a journalist named Ed Hooper, that the Aids epidemic was the result of a terrible human error; that the disease had originally been spread in Africa by a polio vaccine manufactured with the kidneys of infected chimpanzees.
The evidence for this was entirely circumstantial. The Wistar Institute, the drug company involved, denied that it had used chimpanzee kidneys at all in the preparation of the vaccine but there was no doubt that the pattern and timing of the earliest recorded outbreaks in Africa coincided pretty well with the pattern of the vaccination campaigns in the late 1950s. Hamilton saw the story as an awful warning of the dangers of modern medicine. He subsidised Hooper's book, The River, with the profits of one of his prizes; and when the book came out after nine years' labour, he contributed an enthusiastic foreword. It was his efforts to prove the book's story that killed him. In the winter of 1999-2000, he set off to collect chimpanzee shit samples from the Congolese jungle to see if they showed traces of HIV. While in the bush, he felt himself coming down with malaria. The expedition had anti-malarial drugs, and Hamilton was given them. But he also treated himself with insoluble aspirin. No one knows where it came from, but it was found in his gut after it had killed him; for he was also suffering from ulcers, and the aspirin caused a massive haemorrhage in his stomach from which he never recovered. He was only 63.
It was an extraordinary death, although quite of a piece with his attitude to risk and to medicine. He had skied regularly to work across a frozen river in Michigan, skirting holes in the ice. He was proud of his physical prowess, doing pull-ups on trees in his garden, and cycling around Oxford without a helmet even after many accidents, including one where he was thrown through the windscreen onto the back seat of a car and just asked to be driven to hospital. He didn't think modern medicine could save humanity and it is doubtful he would have wanted it to save him.
For his former pupils, and admirers, scattered through the media as well as in the academic world, he was the greatest biologist of the 20th century. John Maynard Smith, Hamilton's only rival for that title in Britain, once called him "the only bloody genius we've got." Robert Trivers, the discoverer of reciprocal altruism, said, "He had the most subtle, multi-layered mind I have ever encountered. What he said often had double and even triple meanings so that, while the rest of us speak and think in single notes, he thought in chords." For The Economist, where Matt Ridley, a former collaborator, and Olivia Judson, a former pupil, had worked, he was the man who "erected... an edifice of ideas stranger, more original and more profound than that of any other biologist since Darwin."
He left his disciples-the word is hardly too strong-with a pious duty to prove true the theory of the origin of Aids for which he had laid down his life. They failed. The first blow to his posthumous reputation came six months after his death, when the theory turned out to be provably false. Hamilton himself had suggested testing the original vaccine for traces of chimpanzee DNA or sequences from HIV. It had been thought, when The River was published, that all the original samples of the vaccine had disappeared. That is why Hamilton's expedition was searching for traces of HIV in wild chimpanzee populations. But a vial of the original batch of the vaccine used in the Congo was found unexpectedly in a freezer at a British research institute and when this was tested, after his death, the results were unequivocal. The vaccine contained no trace of chimpanzee DNA-it was from macaque monkeys, as the Wistar Institute had claimed all along-and it contained no trace of HIV either. Two other independent and highly respected labs analysed samples of the polio vaccine preserved at the Wistar Institute from later campaigns. They found no trace of chimpanzee DNA either. And an epidemiological study released at the same time suggested that the variety of strains of HIV found in the Congo today must descend from a human host. Hooper has still not accepted that these findings destroy his theory, but the scientific world has.
More embarrassment was to follow. Hamilton left behind him the almost completed manuscript of the second volume of his autobiography and this contained a second blow to his friends: a foreword expressing his belief that only a radical programme of infanticide, eugenics, and euthanasia could save the human race from an imminent catastrophe. "I predict that in two generations the damage being done to the human genome by the ante and post-natal life-saving efforts of modern medicine will be obvious to all." He is never specific about what this damage might be. The two concrete examples that he quotes are the heavy spectacles worn by John Maynard Smith and the spread of caesarean sections. Both of these keep alive people who would have died in the stone age and allow them to transmit their genes to future generations. Spectacles he could forgive, although he felt they were symptoms of a larger decadence in the gene pool. But caesarean sections really worried him, and he thought that women should be allowed just one, and then only to save their lives; after that, they should be paid by the state to have no more babies. That way, when civilisation collapsed-as he seems to have thought inevitable-and all births were once more natural, fewer women with genes for narrow hips would be around to die in childbirth.
He decided in his 20s that genocide was partly a response to the spectacle of a competing tribe's population growing. He believed that differential birth rates between groups would lead inevitably to massacres like those in Rwanda or Kosovo. The Kosovo Albanians, he said in his foreword, should be allowed to practice their religion, and even to circumcise their daughters; but they had no right to breed excessively.
He didn't conceal these ideas in his lifetime: his most vigorous defence of euthanasia and infanticide was delivered at a conference in the Vatican organised by the Pontifical Academy of Sciences, where another attendee remembers him saying loudly that he would grieve more for the death of a single giant panda than for that of "a hundred unknown Chinese." People overlooked such views as just further examples of Hamilton's eccentricities. However, the foreword makes it clear that he believed them as a matter of scientific fact: "I suppose the most direct answer to critics is to gather evidence documenting the abundance, the insidiousness, and the inevitability of human deleterious mutation and write a book about it, convince people that something we don't like will happen and we can either forestall it or not. But the matter seems to me so obvious that I won't waste my time."
Now, if one of the greatest scientists of the 20th century believed that catastrophe was so imminent and so obvious, surely lesser scientists should be worried. But they are not. Instead, they are almost paralysed with embarrassment because even the ones who most admire his genius don't believe in the impending genetic doom of the species that was so obvious to Hamilton; and because even his closest friends find his bald expressions of eugenic prejudice upsetting.
Plenty of philosophers and ethicists do believe that some babies are so handicapped that they should not be kept alive by heroic medicine. So do the parents of some of these babies. But Hamilton's way of putting the point was this: "If early signs of a coming severe handicap can be detected, I hold that the kindest thing for the family in which the defective child is to be dependent, and for the child itself, may well be to kill it. It is well known, of course, that such an act can't normally be performed without very persistent psychological consequences for the parents, especially for the mother. But these reactions can still be turned to advantage for what I am calling inclusive happiness... I have little doubt that if trying to survive on Robinson Crusoe's island with my wife I would indeed with my own hands kill a defective baby... I am fairly sure that I should feel sorrow that this had been necessary but no sense of wrongdoing. I believe that my wife would have agreed to the act."
I asked his widow, Christine, from whom he was separated, whether she would in fact have agreed to it. She said that they had discussed, in broad terms, what should happen with a severely handicapped baby. Neither was in favour of heroic medicine. But "there is a world of difference between an idea and the practical reality. Although we did discuss issues such as the one you raise in your letter, and were generally in agreement, my memory is a bit vague on the details.
"In the course of my work I see a number of autistic children who are often quite beautiful, and sense the agony of parents who love their child but can only develop such limited communication with it. The question becomes much more difficult to answer... when the bonds have grown stronger.
"However, in the desert island situation I expect that a severely handicapped infant would not survive anyway. Since we were not put to the test, I can't really answer for either of us."
Perhaps the most disturbing passages in his memoirs concern one of his own brothers. Hamilton was the eldest of seven children, and the boy who followed him died shortly after birth. Hamilton made no bones of his belief that this was a good thing. He was even convinced his mother (herself a doctor) would have wanted the child to die: "Had Jimmy been born today I imagine he might have been saved by an intestinal re-section, but I know from my mother's attitude to all these matters that she would never have allowed it if she could have prevented it... Freya [a dog he loved] deserves to be more loved and remembered than Jimmy to my mind, a statement I think my mother would have understood."
Olivia Judson, a former pupil who wrote one of the most affectionate obituaries of him, was also one of the few people to dare to review what she called his "disturbing" book. In Nature she wrote: "Hamilton is an unabashed, no-fig-leaf naturist. He believes that genetics, not nurture, accounts for a large and important range of human behaviour-from racism and xenophobia to differences in intellectual abilities between men and women-and that only by admitting this, only by casting aside hypocrisy on the matter, can fundamental human problems be tackled. As an example, he argues that a basic cause (emphatically not a justification) of racism-and, particularly, of ethnically motivated genocide-is a differential birth rate between groups. And, yes, he does extend this to the Nazi extermination of Jews." The only other extensive review of the book to have appeared was by another sociobiologist, the writer Marek Kohn, who drew a comparison between Hamilton's beliefs and the fascist and antisemitic sympathies of TS Eliot.
Richard Dawkins, who delivered the eulogy which is reprinted as the book's foreword, has declined all invitations to review the book. If only Hamilton had lived, says Dawkins, his friends would have persuaded him to tone down the manuscript, and explained the things that cannot be said in polite society.
Mark Ridley, another Oxford biologist, was both a friend and collaborator of Hamilton's: he helped to edit the manuscript after Hamilton's death, and was thus confronted with his views in their sharpest form. He felt he could not remove the bits that he found offensive or wrong: "I disagree with the genetics and the politics, and I think it's not compellingly argued. But sometimes Bill would see something was right and not bother to argue the position, especially with something as controversial as human genetics. And he was such a genius that you wouldn't want to censor him. It would be too embarrassing if you deleted something and someone found out 25 years later, when the idea had been given six Nobel prizes. It would be like editing Moses."
Alan Grafen, now Oxford's leading theoretical biologist, believes that Hamilton may have been a prophet: "There is a gnostic sense that many geneticists have that if one interprets things in terms of a special priestly knowledge of genes, it leads you to different conclusions from the rest of the world." And although Grafen points out that Hamilton was right about many things, he doesn't sound like a man convinced that the world faces catastrophe within three generations: "Whether or not mutational meltdown is an urgent question is not something I have considered. I hesitate to dismiss it entirely. The question is whether humans will be better off in a million years as a result of modern medicine. Mass extinctions do happen, you know. In the long run, medicine may have made our situation more precarious."
Paul Harvey, the head of the zoology department where Hamilton worked, says Hamilton wanted big solutions to big problems. He made his name by showing mathematically how self-sacrificing behaviour can arise and flourish in a Darwinian world. After that, he worked on a grand theory of sex. Harvey thinks it in character that he wanted a grand theory of the fate of humanity.
But the oddest and most embarrassing thing about Hamilton's fears for humanity is that they contradict the theory of sex on which he spent the last 20 years of his life. All biologists are agreed that what makes sex a good idea is death-at least in evolutionary terms. Sexual creatures shuffle their genes around, which ensures that the bad ones are unequally distributed. Some bodies end up with lots of them, and others with none; the ones with lots of bad mutations die quickly, which keeps the rest of the gene pool clean.
The great argument, on which Hamilton spent most of the last 20 years of his life, is about what exactly makes genes malfunction so often that they must be discarded by the radical and expensive method of sex. One side in this argument believes that the enemy of the genome is simply random mutation, which produces so many bad genes in every generation that the sexual shuffling of mutations is the only way to produce some bodies that have only good copies of genes.
The second theory holds that what makes genes "bad" is not the malfunctions produced by mutation but a more subtle inadequacy: the last generation's genes are unlikely to have enough resistance to this generation's parasites and disease-causing organisms. Parasites have much shorter lives than the creatures they attack, so if some of their mutations help them to outwit their hosts' defences they will develop new weapons far faster than the creatures they attack. This disparity works even more to the advantage of pathogens such as bacteria and viruses.
Genes can be seen as our defences against a hostile environment; faulty genes leave us with weak spots. It is only by shuffling the genes for disease resistance around with sex that large and relatively slow-breeding organisms can defend themselves. It was this theory of sex that Hamilton passionately defended. He argued, for instance, that the gorgeous displays of birds like peacocks were advertising the health and freedom from parasites of a really glossy specimen. He would have loved the modern slang term "fit" because he thought that our judgements of who and what is worth mating with are actually judgements about their health and condition.
But this makes all the more extraordinary his belief-expressed in the prefaces to the papers-that human beings are threatened by the medical suppression of mutation and not of disease. The kind of high-tech modern medicine that horrified him has very little effect on the gene pool, if only because most of the beneficiaries are past breeding anyway. In western countries, up to half of the expenditure on health over a person's lifetime comes in the last six months of their lives. The number of babies rescued from death by high-tech medicine is certainly larger than it was 100 years ago, but it is still pretty low.
The statistics of infant mortality show clearly that the real selection pressure on the human race comes from parasites and pathogens. In those parts of the world where natural selection still operates on humans with unhampered cruelty, the figures are staggering. According to one estimate, in 1998, wars killed 308,000 people in Africa alone, but diarrhoeal disease killed more than twice as many.
We in the developed world have relaxed the pressures of natural selection. We do not expect 40 per cent of our children to die, as they used to in Europe, and still do in traditional peasant societies. So in one sense, we are inviting dysgenic mutations and there is some evidence that they are building up, although not at the rate Hamilton supposed. But the medical and technological advances which have led to this have nothing to do with high-tech maternity hospitals, caesarean sections or the preservation of obviously handicapped children. The things that have removed the sting from natural selection are clean water, adequate food and vaccinations. So any serious Hamiltonian programme to clean up the human gene pool would start with the abolition of antibiotics, of vaccination, and of sewage works. All that would be left of modern medicine, if we were to adopt a rigorously eugenic stance, would be surgery and painkillers. These seem to have been the only forms of medicine that Hamilton approved for himself. (There is a hideous irony in the circumstances of his death, caused indirectly by the malaria parasite, but directly by his own treatment of himself with the low-tech painkiller aspirin.)
But should the weirdness and wrongness of his eugenic fears discredit the rest of his ideas? Some evolutionary psychologists fear that this will happen. The association between genetics, eugenics and fascism is already embedded amongst many people on the left. Hamilton was not a racist: in fact, his eugenics led him to completely anti-racist conclusions and to an enthusiastic advocacy of miscegenation. He believed that crosses between human races were a wonderful and perhaps necessary way to improve humanity, by blending our various resistances.
That is not racist; but it is far from the pieties of what is normally meant by anti-racism. There is no doubt that fear of supplying ammunition to the enemies of sociobiology contributes to the reluctance of pro-Hamilton scientists to say anything about the book. Yet the fact that some of Hamilton's ideas were absurd does not contaminate the rest of them. In fact, there is almost a tradition among great evolutionary biologists of stupid or downright wicked political beliefs. Konrad Lorenz was an enthusiastic Nazi in the 1930s; in Britain, at the same time, JBS Haldane was a committed communist throughout the years of Stalinism. RA Fisher, who united genetics with Darwinism in the 1930s, spent the last five chapters of his book The Genetical Basis of Natural Selection on an extraordinary argument to prove that civilisation was threatened because upper-class women never had enough babies.
Hamilton's political ideas were far less harmful than those of Lorenz or Haldane. Yet in his prefaces it is easy to find many of the ideas that made fascism attractive in the 1930s: the admiration for nature, the distrust of democracy and the pose of doomed heroic stoicism. There is in Hamilton a remorseless pessimism of the intellect, a certainty that things will end wrongly, the evidence for which is tempting for liberals to overlook or forget. In his case, a pessimism of the intellect was balanced by a tremendous relish in life, a kind of optimism of the imagination.
"He didn't particularly value human beings above animals," says Alan Grafen, and almost his most famous essay was a request, first published in a Japanese journal of entomology, that his body be left out in the Amazon jungle to be chewed up by one of his favourite species of beetle, and used to nourish their larvae. The wish was entirely characteristic of the man and so, too, was the fact that he never bothered to get his will witnessed and was buried conventionally in a country churchyard in Oxfordshire.