An intellectual war of words has broken out between two of the world's leading evolutionists. Oxford University's Richard Dawkins and Harvard's Edward Wilson have gone head to head over the evolution of altruism in the animal kingdom, and whether it can have come about as a result of something called group selection.
The subject matter of their dispute is social insects, particularly ants, which display a supreme form of altruism in that sterile workers lay down their lives for the benefit of their fertile colleagues in the colony.
Conventional Darwinian theory could not really explain why one individual should sacrifice its own life, and its precious genes, for the benefit of another individual, unless it could be viewed in terms of group selection, when indi-viduals do it for the benefit of the colony or the species.
But nearly half a century ago, scientists punched intellectual holes in the theory of group selection and pointed instead to something called kin selection, when altruism in social communities evolves as a result of one individual being closely related to a member of the same colony.
Social insects such as ants display unusual degrees of relatedness within the colony, with sister workers being more closely related to one another than to the offspring they may have. It was therefore seen as beneficial for individual sisters to sacrifice their fertility for their sister queen because of the genes they had in common.
Mathematical models supported kin selection which rose to prominence because it appeared to explain the evolution of altruism in ants and many other species. Group selection was dead in the water. But now Professor Wilson has brought it back to life in a book on ants to be published this year, and in an interview this week with New Scientist magazine.
"If you look at the literature of the theory, there are a lot of impressive-looking mathematical models but they scarcely ever come up with a real measure of anything that can be applied to nature," he says.
This has not pleased Professor Dawkins who, while he has respect for Wilson, spent much of his early career exploding the myth of group selection, which is anathema to the "selfish gene" theory behind kin selection.
In a separate article in New Scientist, Dawkins acknowledges Wilson's "characteristically fascinating account" of the evolution of social insects, but says: "His 'group selection' terminology is misleading, and his distinction between 'kin selection' and 'individual direct selection' is empty."
What matters is natural selection at the level of the gene, not the group, he insists. "All we need ask of a purportedly adaptive trait is, 'what makes a gene for that trait increase in frequency?' Wilson wrongly implies that explanations should resort to kin selection only when 'direct' selection fails," says Dawkins.
"Here he falls for the first of my '12 misunderstandings of kin selection'; that is, he thinks it is a special, complex kind of natural selection, which it is not."
Dawkins points out that Wilson relegates kin selection to a chapter on group selection in his book Sociobiology, published in the mid-Seventies. "Evidently Wilson's weird infatuation with 'group selection' goes way back; unfortunate in a biologist who is so justly influential," he says.
Professor Wilson remains convinced that he will be proved right, and his critics wrong.
"I am used to taking the heat, and in the past I turned out to be right," he said.
Sacrifice in the natural world
* Mothers in many animal species will risk injury and even death to protect their young. This is seen as a prime example of kin selection and can explain why people will tolerate their own children's behaviour but not that of others.
* Many social animals demonstrate acts of altruism based on close kinship within the colony. The supreme form of altruism is seen in social insects, when individuals sacrifice their fertility and lay down their lives for the benefit of their fertile queen.
* Some species engage in what is known as reciprocal altruism, when an altruistic act is carried out in the expectation that it may be returned later on. Warning calls of birds in response to potential danger are thought to be an example of reciprocal atruism. The call puts the bird at higher risk, but it will benefit it in the long run if others reciprocate.