Issn 1471-0498 Department of Economics Discussion Paper Series Group Selection and the Evolution of Altruism

“Group selection” is often cited as an explanation for the survival of altruism. The idea of group selection is a controversial one — much effort has been expended on its justification (and refutation). Relatively little effort has gone into formally testing whether or not it can actually provide a reasonable explanation for altruistic behaviour. This paper concentrates solely on whether or not a group structure enables the survival of altruism in an evolving population. If altruism is to flourish either groups need to be isolated from each other for multiple generations, or groups themselves need to constructed in a positively assortative manner. In the former case the size of the group, the relative benefit to cost of altruism and the number of generations in isolation play a crucial role in determining the survival chances of altruism. In the latter case, when groups are short-lived phenomena, a precise condition is given on the assortative mechanism for the survival of altruism in the long run. The probability distribution of the dispersion-rematching process and the group size are of critical importance in this case.