The first answer, proposed by the great British biologist William Hamilton and popularised by Dawkins in his book The Selfish Gene, is “kin selection”. Genes exist to replicate themselves. This is ideally done by ensuring that the individual reproduces. But it might also be done by ensuring that relatives of the individual reproduce because they share many of the same genes. So altruism starts with family members. Altruism towards strangers, meanwhile, is explained by game theory - computer models show that a cautiously benign approach to strangers is the best evolutionary strategy. Either way, Dawkins’s “selfish gene” is at the heart of the whole process.
“Kin selection was a very seductive idea,” Wilson explains, “and I promoted it heavily in my books in the 1970s. Unfortunately it has produced a little industry with its own mathematical models. It hasn’t produced much else and, meanwhile, sociobiology has flourished.”
“We are united in our view of group selection,” the Wilsons [E.O. and David Sloan Wilson] concluded, “which we converged upon through separate lines of inquiry.” Group selection says that evolution acts on many levels. Take the ants again. “They are constantly at war,” says Wilson. “Give ants nuclear weapons and the world would be destroyed in a week.”
Warring ants will be better off if the entire fitness of the colony can be improved. If it is improved then the methods of that colony will be successful in war and the genes that carried the improvement will be disseminated to a wider ant population. Kin selection may play a part within the colony. But group selection is the far more potent evolutionary force. In his next book Wilson is to study the implications of this new paradigm for humans. Knowing him, it may well turn out to be the first great scientific statement of the 21st century.
From a EurekAlert release:
Eusociality is a challenge for biologists to understand because worker castes in eusocial species forgo individual reproduction but rear young that are not their own, a behavior that biologists label altruistic. Wilson’s current view about eusociality differs from the assessment in his seminal book Sociobiology: The New Synthesis (1975). According to that widely accepted earlier account, selection acting on individuals that are related (kin selection), rather than on whole colonies, explains eusociality in Hymenoptera. Kin selection is thought to be especially powerful in these animals because of an unusual genetic system, known as haplodiploidy, that they share.
Wilson’s survey in BioScience, which examines the findings of a number of researchers, points out aspects of the occurrence of eusociality that the standard explanation has difficulty accounting for. Eusociality has evolved only a few times, and not all of them were in haplodiploid species. Furthermore, the great majority of haplodiploid species are not eusocial. Wilson holds that selection acting on traits that emerge at a group level provides a more complete explanation for eusociality’s rare instances than kin selection. Kin selection is, he writes, “not wrong” but incomplete.