Altruism is one of those delightful things about biology that at the outset, doesn’t make a lot of sense. The concept of altruism is that an organism undertakes actions that come at some cost or risk to it, but these benefit another organism. This altruism can take elaborate forms in social animals, and in humans, be codified as a system of morality or ethics. Nonetheless, altruism- and the ability to act consistently within some social rules- is common to all social species. Ants and humans undertake actions that can require sacrifices for the group. Murder (or predation) is eschewed within a group.
The puzzle would seem to be why would an organism bear this risk or cost? Risks for instance, may come from participating in joint defense of a group. Costs come from providing say, resources or forgoing opportunities to another.
The answer however is somewhat subtle. The evolutionary rule isn’t about the survival of the organism. At a biological level, organisms are a means to transmit genes from one generation to the next. So the point is not to evaluate morality in the context of what happens to the individual. It is to evaluate it in terms of what happens to the genes.
This first insight was elaborated by Bill Hamilton in the 1960s. Hamilton developed the kinship mechanism for the selection of altruism. This recognises that there are two ways an organism can transmit its genes to the next generation. One is directly through its own efforts. The other is indirectly through other close relatives. This explains why in social insects- bees, wasps, ants- social behaviour is common. (In fact, social organisation of the ants has probably made them one of the most successful organisms on the planet. They are found nearly everywhere and in high densities in many natural habitats).
The peculiar biology of ants, bees and wasps is that sex is determined by whether an organism is haploid or diploid. (In mammals, both sexes are diploid, in bees, ants and wasps the males are haploid, females are diploid). The biological consequences are that each female ant is even more closely related to her sister’s offspring than would be the case in mammals. This makes evolution of altruism in such insects far more likely.
The second evolutionary mechanism for altruism is reciprocation. This was developed by Robert Trivers in 1971. The principle here is that there may be gains from reciprocation that encourage altruism. For example, social spiders often combine webs and cooperate to bring down larger prey that a single spider would be too small to take-down. The society of spiders within the combined web, follows certain social rules also. Contributing resources (spider silk) to the community comes at a cost, but is sustained by other spider’s willingness to share larger prey.
Both kinship and non-kinship mechanisms act strongly in humans. Most early human communities would have been closely related genetically. Reciprocation would have led to gains in three major areas of human groups. The first is in terms of mutual defense. Being able to act as a team to defend against predators or the like generates an evolutionary advantage. The second is in terms of hunting. Again, the ability to act as a team to take down large prey would be selected for. The third is in terms of child care. Humans invest heavily time and resources into raising infants. Reciprocation- joint community care of juveniles- would lead to another evolutionary advantage.
Since then research on the evolution of altruism has continued. Dawkins used the earlier work of Trivers and Hamilton in his book The Selfish Gene. Axelrod and Hamilton extended the work on reciprocation in the mind-1980s with work on repeated Prisoner’s Dilemma and search for evolutionary stable strategies towards cheating. Axelrod showed that of a number of strategies, tit-for-tat (a simple reciprocation rule mimicking ‘the golden rule’) had the highest payoff in repeated encounters. In effect, it would be selected for.
Research building on and elaborating these approaches has continued. A check of the ISI Web of Knowledge database shows that 780 papers on evolution of altruism have been published in just the last 5 years.
In short, much of our social instincts and moral rules have an evolutionary basis