Human Self-Domestication by Intersexual Selection: Female Social Status and Stature Sexual Dimorphism

Abstract

This research examines one of the three primary mechanisms currently proposed to explain apparent self-domestication in Homo sapiens—that is, intersexual selection against reactive aggression. My central hypothesis is that human self-domestication has been, at least in part, caused by context-dependent female preferences for less-aggressive males. Following from this, I expect that societies where women have both higher social status and secure access to nutritional resources will tend to show relatively elevated signs of human self-domestication—as indicated by lower stature sexual dimorphism. In essence, I predict an interaction between female status and food security in shaping stature sexual dimorphism. To facilitate a cross-cultural test of my functional hypothesis, I collected male and female stature data for 92 of the 186 societies in the Standard Cross-Cultural Sample. These data allowed for a multivariate-regression, multimodel-inference analysis of the relationship between stature sexual dimorphism, and female social status and food security. Controlling for confounding factors such as shared cultural ancestry and mean body size, the analysis revealed strong evidence for the hypothesized interaction between the two predictors of interest in shaping the outcome variable. Overall, this study expands upon the findings of several previous investigations into human stature sexual dimorphism, whilst contradicting some others and providing directions for further investigation. The principle conclusion of this work is that context-dependent female mate choices significantly contribute to a lessening of stature sexual dimorphism and, therefore, are likely to have played an important role in the self-domestication of our species.