The Effect of Female Social Status on Human Stature Sexual Dimorphism: Evidence of Self-Domestication?

Abstract

Charles Darwin noted that domesticated mammals share multiple traits when compared to their wild ancestors. These shared characteristics are known to occur following breeding selection against aggression. Domesticated traits are also apparent in modern humans when compared to earlier Homo sapiens, which has led researchers to propose that a form of human ‘self-domestication’ has occurred. One of three hypotheses proposed to explain this process suggests that human females preferentially selected against aggressive male partners. Over time, this would lead to lower aggression, as well as other domesticated traits across our species, including reduced body size difference (dimorphism) between the sexes. In all human populations mean male stature is always greater than mean female stature, however, the relative magnitude of stature sexual dimorphism (SSD) varies. In order to test the hypothesis that self-domestication was effected through female mate choice, this study examines whether elevated female social status (hence higher female capacity to exercise mate choice) is associated with lower levels of SSD in different human populations. To do so, SSD data were compared with selected statistically-coded variables from the Ethnographic Atlas (a cross-cultural sample of 1267 societies). Linear regression models were used to assess correlations between SSD and variables associated with female social status. After controlling for world region and latitude, matrilineal property inheritance remained a significant predictor for lower SSD. This result may lend weight to the hypothesis that female mate choice was a contributory mechanism in human self-domestication, however, further empirical investigation is required.