Human preferences for sexually dimorphic faces may be evolutionarily novel

A large literature proposes that preferences for exaggerated sex typicality in human faces (masculinity/femininity) reflect a long evolutionary history of sexual and social selection. This proposal implies that dimorphism was important to judgments of attractive- ness and personality in ancestral environments. It is difficult to evaluate, however, because most available data come from large- scale, industrialized, urban populations. Here, we report the results for 12 populations with very diverse levels of economic develop- ment. Surprisingly, preferences for exaggerated sex-specific traits are only found in the novel, highly developed environments. Sim- ilarly, perceptions that masculine males look aggressive increase strongly with development and, specifically, urbanization. These data challenge the hypothesis that facial dimorphism was an im- portant ancestral signal of heritable mate value. One possibility is that highly developed environments provide novel opportunities to discern relationships between facial traits and behavior by ex- posing individuals to large numbers of unfamiliar faces, revealing patterns too subtle to detect with smaller samples.