Sex-Specific demography and the evolution of gender-biased harmful cultural practices
Cultural practices that are harmful to one sex, but favour the other, are the focus of intense interest in the public eye, the social sciences and the evolutionary human sciences. The foundational work of Hamilton, Bateman and Trivers, showed how kin selection theory provides a framework for understanding the evolutionary basis of conflicts of interest between the sexes and between parents and offspring. However, many gender-biased practices do not seem to fit this classic model of sexual conflict, in which males exploit females for their own mating advantage. Rather than focus on the inherent differences in sexual strategies of males and females, I will explore an alternative explanation, which is sex-specific demography. This framework refocuses attention away from sexual selection, towards patterns of cooperation and conflict within families. If one sex disperses at marriage, that generates sex and age-based asymmetries in relatedness in residential groups, but few theoretical models, or empirical studies, have examined how such demographic effects could explain the origins of gender-biased cultural behaviour. EvoBias will develop and test new evolutionary demographic models that will focus on the role of sex-ratios, sex-biased dispersal and some modes of marriage, in generating gender-biased harmful cultural practices. The behaviours to be studied include: female-biased workloads, witchcraft accusation, sending men to war, sending boys into monastic life, bride-capture and the ‘honour’ killing of women by their own kin. These represent both social issues and evolutionary puzzles. The diverse kinship systems in east and central Asia and sub-Saharan Africa provide opportunities to test these hypotheses. Through a combination of mathematical modelling, comparative studies using the literature and field-based sociodemographic studies, the team will seek evidence that sex-specific demography underpins these gender-biased harmful cultural traditions.