they sting, trying to save the hive; birds warn each other of predators or help to feed their young siblings; even human beings are prepared to die in acts of selfless heroism to save others ' lives. But as we shall see, the appearance is misleading. Animal altruism is a myth. Even in the most spectacular cases of selflessness it turns out that animals are serving the selfish interests of their own genes—if sometimes being careless with their bodies.
THE REDISCOVERY OF THE INDIVIDUAL
If you attend a meeting of evolutionary biologists somewhere in America, you might be lucky and spot a tall, gray-whiskered, smiling man bearing a striking resemblance to Abraham Lincoln, standing rather diffidently at the back of the crowd. He will probably be surrounded by a knot of admirers, hanging on his every word—for he is a man of few words. A whisper will go around the room:
'George is here.' You will sense from people's reactions the presence of greatness.
The man in question is George Williams, who has been a quiet, bookish professor of biology at the State University of New York at Stony Brook on Long Island for most of his career. He has done no memorable experiments and has made no startling discovery. Yet he is the progenitor of a revolution in evolutionary biology almost as profound as Darwin 's. In 1966, irritated by Wynne Edwards and other exponents of group selection, he spent a summer vacation writing a book about how he thought evolution worked. Called
In the book Williams exposed the logical flaws in group selection with unanswerable simplicity. The few evolutionists who had stuck to individual selection all along, such as Ronald Fisher, J. B. S. Haldane, and Sewall Wright, were vindicated.' The ones who had confused species and individual, such as Julian Huxley,
were eclipsed. 16 Within a few years of Williams 's book, Wynne Edwards was effectively defeated, and almost all biologists agreed that no creature could ever evolve the ability to help its'species at the expense of itself. Only when the two interests coincided would it act selflessly.
This was disturbing. It seemed at first to be a very cruel and heartless conclusion to reach, particularly in a decade when economists were tentatively celebrating the discovery that the ideal of helping society could persuade people to pay high taxes to support welfare. Society, they said, need not be based on tempering the greed of individuals but on appealing to their better natures. And here were biologists coming to exactly the opposite conclusion about animals, depicting a harsh world in which no animal ever sacrificed its own ambition to the need of the team or the group: Crocodiles would eat one another 's babies even on the brink of extinction.
Yet that was not what Williams said. He knew full well that individual animals often cooperate and that human society is not a ruthless free-for-all. But he also saw that cooperation is nearly always between close relatives— mothers and children, sister worker bees—or that it is practiced where it directly or eventually benefits the individual. The exceptions are few indeed. This is because where selfishness brings higher rewards than altruism, selfish individuals leave more descendants, so altruists inevitably become extinct. But where altruists help their relatives, they are helping those who share some of their genes, including whatever genes had caused them to be altruistic. So without any conscious intention on the part of individuals, such genes spread.'
But Williams realized that there was one troubling exception to this pattern: sex. The traditional explanation for sex, the Vicar of Bray theory, was essentially group selectionist. It demanded that an individual altruistically share its genes with those of another individual when breeding because if it did not, the species would not innovate and would, a few hundred thousand years later, be outcompeted by other species that did. Sexual species, it said, were better off than asexual species.
But were sexual
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not, sex could not be explained by the Williams ' selfish ' school of thought. Therefore, either there was something wrong with the selfish theories and true altruism could indeed emerge, or the traditional explanation of sex was wrong. And the more Williams and his allies looked, the less sense sex seemed to make for the individual as opposed to the species.
Michael Ghiselin of the California Academy of Sciences in San Francisco was at the time engaged in a study of Darwin 's work and was struck by Darwin 's own insistence on the primacy of the struggle between individuals rather than the struggle between groups: But Ghiselin, too, began thinking about how sex seemed such an exception to this. He posed the following question: How could a gene for sexual reproduction spread at the expense of an asexual gene? Suppose all members of a species were asexual but one day one pair of them invented sex. What benefit would it bring? And if it brought no benefit, why would it spread? And if it could not spread, why were so many species sexual? Ghiselin could not see how the new sexual individuals could possibly leave behind more offspring than the old asexual ones. Indeed, surely they would leave fewer because, unlike their rivals, they had to waste time finding each other, and one of them, the male, would not produce babies at all.1e
John Maynard Smith, an engineer-turned-geneticist at the University of Sussex in England, with a penetrating and somewhat playful mind that had been trained by the great neo-Darwinist J. B. S. Haldane, answered Ghiselin 's question without solving his dilemma. He said that a sexual gene could spread only if it doubled the number of offspring an individual could have, which seemed absurd. Suppose, he said, turning Ghiselin 's thought around, that in a sexual species one day a creature decides to forgo sex and put all of its genes into its own offspring, taking none from its mate. It would then have passed twice as many genes on to the next generation as its rivals had. Surely it would be at a huge advantage. It would contribute twice as much to the next generation and would soon be left in sole possession of the genetic patrimony of the species.19
Imagine a Stone Age cave inhabited by two men and two
women, one of them a virgin. One day the virgin gives birth 'asexually ' to a baby girl that is essentially her identical twin. (She becomes, in the jargon, a 'parthenogen. ') It could happen in several ways— for example, by a process called 'automixis, ' in which an egg is, roughly speaking, fertilized by another egg. The cave woman has another daughter two years later by the same means. Her sister, meanwhile, has had a son and a daughter by the normal method.
There are now eight people in the cave. Next, the three young girls each have two children and the first generation dies off. Now there are ten people in the cave, but five of them are parthenogens. In two generations the gene for parthenogenesis has spread from one-quarter to one-half of the population. It will not be long before men are extinct.
