Cross-racial Consistency of Sexual Dimorphism in Facial Forms: Comparisons Between Turkish and Japanese Populations

Abstract

Facial features may reflect an individual’s probability of survival because of natural selection—for example, through reproduction and feeding abilities. However, questions remain about which facial characteristics contribute to facial masculinity and/or femininity across races. Given that sexual dimorphism stems from the common natural selection process, it is hypothesized that there is cross-racial consistency in sexual dimorphism of facial forms. Examining the extent to which sex differences in facial soft tissue configurations are similar across diverse populations could suggest the source of the indirect evolutionary benefits of facial sexual dimorphism traits. To explore this idea, we selected two geographically distinct races. Three-dimensional model faces were derived from 272 Turkish and Japanese men and women; their facial morphologies were evaluated using landmark and surface-based analyses. We found four common facial features related to sexual dimorphism. Both Turkish and Japanese females had a shorter lower face height, a flatter forehead, greater sagittal cheek protrusion in the infraorbital region but less prominence of the cheek in the parotid-masseteric region, and an antero-posteriorly smaller nose when compared with their male counterparts. We also discussed the possible phylogenetic contribution of masticatory organ function and morphogenesis on sexual dimorphism of the human face.

Facial and body sexual dimorphism are not interconnected in the Maasai

“…Maasai being one of such examples. Some findings suggest that prenatal testosterone exposure may affect the sexually dimorphic facial morphology [ 17 ], and androgens in males could contribute to facial sexual dimorphism both before and after puberty [ 34 ]. The data from two traditional East African populations, one of which is seminomadic pastoralists similar to Maasai in their ecology and cultural patterns (the Datoga), pointed to the potential role of androgen receptor gene polymorphism in male aggression and reproduction (number of offspring born) [ 148 , 149 ].…”

“…Some studies demonstrated that females prefer more masculine male partners, and males, in turn, more feminine looking females in such environment or in the absence of high-quality medical help [ 153 ]. It remains to be found out in the future, which sexually dimorphic traits may enhance individual survival probability to different degrees in males and females and show lesser variations between populations of modern humankind [ 34 ].…”