Key concepts reciprocal altruism, xenophobia, game theory, prisoner's dilemma, evolutionarily stable strategy, tit-for-tat, stereotyping, ethnocentrism, self-concept

Most animals live relatively solitary lives, occasionally meeting up only to copulate, threaten or fight with each other. But some species live in groups where they constantly interact. Students of animal behaviour have long asked what benefits do individual organisms accrue from living in such social groups? According to evolutionist Richard Alexander, ‘Complex sociality should be expected to arise only when confluences of interest produce benefits that override the costs of conflicting interests’ (Alexander, 1987, p. 65). He sees the seeds of animal social behaviour as arising out of the need for cooperative defence and the production of mutual offspring. In recent years theories concerning altruism, which have been developed to explain animal social behaviour, have also been used by evolutionary psychologists to study human social behaviour. So do we thrive in the company of others for the same reasons as other social animals?