Survival of the Aggressive? Behaviour and beliefs related to male aggression: evidence of intrasexual selection in humans?

Abstract

Sexual selection favours traits that increase mating and, thus, reproductive success. As termed by Darwin: intersexual selection occurs between mates, i.e. a peacock’s plumage is a result of females favouring these impressive and colourful feathers. Intrasexual selection however occurs between members of the same sex over mates and results in armaments, i.e. the horns on a stag give him an advantage when fighting other males for access to females. Some scholars have suggested that if intrasexual selection is driven by contest competition, this has shaped human male aggression. If this is the case, one testable hypothesis is that beliefs and behaviour related to male aggression should be more prevalent in societies where the intensity and strength of sexual selection is higher. Measured by factors such as the presence and scope of polygyny (one male mates with multiple females), the number of same-sex competitors relative to potential mates (sex ratio), and male contribution to subsistence activities. We used data from 78 societies from the Standard Cross Cultural Sample, a widely used ethnographic data set combining years of data collection from many societies around the world. We found strong support for this hypothesis. We discuss potential alternative explanations for the relationships, ruling out some using multivariate methods to control for confounding variables such as political complexity, warfare and geographic clustering.