The so-called universal sex differences have been shown to be more pronounced in Western industrial societies than in most non-Western developing societies; a possible reason is less consanguineal marriages in the first group

Evolution, Societal Sexism, and Universal Average Sex Differences in Cognition and Behavior. Lee Ellis. In Oxford Handbook of Evolution, Biology, and Society, Edited by Rosemary L. Hopcroft, Apr 2018. DOI: 10.1093/oxfordhb/9780190299323.013.30

Abstract: During the past century, social scientists have documented many cross-cultural sex differences in personality and behavior, quite a few of which now appear to be found in all human societies. However, contrary to most scientists’ expectations, these so-called universal sex differences have been shown to be more pronounced in Western industrial societies than in most non-Western developing societies. This chapter briefly reviews the evidence bearing on these findings and offers a biologically based theory that could help shed light on why cross-cultural sex differences exist. The following hypothesis is offered: The expression of many genes influencing sexually dimorphic traits is more likely among descendants of couples who are least closely related to one another. If so, societies in which out-marriage is normative (i.e., Western industrial countries) will exhibit a stronger expression of genes for sexually dimorphic traits compared to societies in which consanguineal marriages are common.

Keywords: social role theory, evolutionary theory, evolutionary neuroandrogenic theory, sex egalitarian societies, sex differences, personality traits