Human preferences for sexually dimorphic faces may be evolutionarily novel

Abstract

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 attractiveness 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 development. Surprisingly, preferences for exaggerated sex-specific traits are only found in the novel, highly developed environments. Similarly, perceptions that masculine males look aggressive increase strongly with development and, specifically, urbanization. These data challenge the hypothesis that facial dimorphism was an important 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 exposing individuals to large numbers of unfamiliar faces, revealing patterns too subtle to detect with smaller samples.

Keywords: aggression; cross-cultural; evolution; facial attractiveness; stereotyping.

Fig. 1.

Examples of stimuli used. A European female composite (Upper) and an East Asian male composite (Lower) are shown. Masculinized stimuli (Left) and feminized stimuli (Right) are shown.

Fig. 2.

(A) Preferences for sex dimorphism in female faces, by group. Blue sections indicate the proportion of a group that chose masculinized faces as most attractive, white sections indicate the proportion that chose neutral faces, and pink sections indicate the proportion that chose feminized faces. (B) Preferences for sex dimorphism in male faces, by group. Blue sections indicate the proportion of a group that chose masculinized faces as most attractive, white sections indicate the proportion that chose neutral faces, and pink sections indicate the proportion that chose feminized faces.

Fig. 3.

Preferences for sex dimorphism in male faces by level of disease burden. Female preferences for masculinity in male faces by group, expressed as an average [participants’ choices for most attractive male faces were recorded as +60 (feminine), 0 (average), or −60 (masculine)], plotted against years lost to infectious disease in local populations (log-transformed). Preferences for masculinity decrease as the disease burden increases.

Fig. 4.

Male faces perceived as most aggressive-looking, by group. Blue sections indicate the proportion of a group that chose masculinized faces as most aggressive, white sections indicate the proportion that chose neutral faces, and pink sections indicate the proportion that chose feminized faces.

Fig. 5.

Masculinity of male faces perceived as most aggressive-looking, by level of urbanization. Average levels of masculinity in the male faces chosen as most aggressive-looking by group, plotted against level of urbanization, are shown. Participants in urban environments were more likely to choose masculine faces when asked to choose the most aggressive-looking face.