The evolution of human altruism towards non-kin through sexual selection

Altruistic or selfless behaviour is a major puzzle for evolutionary biology which predicts competition between organisms in the struggle for existence. One explanation for altruism towards non-kin proposes that it evolved as a reliable signal of individual quality to others, including potential mates. It is thus possible to see altruistic traits as handicaps that act as indicators of the phenotypic and genetic quality under sexual selection. Here, I also suggest that sexual selection mechanisms other than the handicap principle might have favoured the evolution of altruism towards non-kin. I focus on human altruistic traits and speculate that the expansion of the brain in human evolution would have made increasing levels of parental investment essential. If displays of altruism towards non-kin had correlated with sustained parental investment then conditions particularly favourable to the evolution of altruistic traits could have existed. I make three predictions based on this scenario, each of which requires measurement of mate preference towards altruistic traits. I therefore develop and test a psychometric scale to measure this mate preference. Firstly, I predict that mate choice on the basis of altruistic traits will be found, a prediction supported in one sub-sample. Secondly, I predict significantly stronger female mate preference towards altruistic traits, a prediction that is also supported. Finally, I predict that, in line with sexual selection theory, variation in mate preference and preferred trait will be subject to genetic influence. This prediction is supported in a twin study of responses to the scales employed. I also examine one form of altruistic behaviour, voluntary activity on behalf of others, and measure six possible motivations to perform this behaviour. I conclude that one motivation alone, altruistic motivation, accounts for volunteer commitmentEThOS - Electronic Theses Online ServiceGBUnited Kingdo