The origins of selflessness: Fair play

The Economist:

FOR the evolutionarily minded, the existence of fairness is a puzzle. What biological advantage accrues to those who behave in a trusting and co-operative way with unrelated individuals? And when those encounters are one-off events with strangers it is even harder to explain why humans do not choose to behave selfishly. The standard answer is that people are born with an innate social psychology that is calibrated to the lives of their ancestors in the small-scale societies of the Palaeolithic. Fairness, in other words, is an evolutionary hangover from a time when most human relationships were with relatives with whom one shared a genetic interest and who it was generally, therefore, pointless to cheat.
The problem with this idea is that the concept of fairness varies a lot, depending on which society it happens to come from–something that does not sit well with the idea that it is an evolved psychological tool. Another suggestion, then, is that fairness is a social construct that emerged recently in response to cultural changes such as the development of trade. It may also, some suggest, be bound up with the rise of organised religion.