Sexual Dimorphism in Facial and Body Shape and Their Relationship in Modern Humans of African, Asian, and European Descent

OBJECTIVES: Our study aimed to quantify the degrees of sexual dimorphism in facial shape and nineteen body parameters across eleven living populations from three major world regions: Sub-Saharan Africa (five populations), Europe (three populations), and Asia (three populations). METHODS: The data were collected in Tanzania and Russian Federation (N = 2214 individuals, aged 16-35 years), utilizing identical methods. Facial shape was explored through geometric morphometrics based on photographs. Body parameters were obtained through direct measurements. RESULTS: We found that body parameters are highly sexually dimorphic in humans and have population specificity: in taller and more robust populations (Europeans, Asians), body height, bone mass, handgrip strength, and wrist diameter are the most dimorphic traits, whereas Africans demonstrate the highest variability in body dimorphism. In contrast, the degree of facial sexual dimorphism increases from minimum in Africans to intermediate in Asians and maximum in European populations. Sexually dimorphic facial shape patterns vary by population origin, with allometry on average explaining over half of the sex differences. We did not find a linear relationship between overall degrees of body and facial dimorphism across study populations. However, dimorphism in several isolated body parameters correlated with facial dimorphism at the population level. Particularly, for body height, handgrip strength, and bone mass, such correlations remained evident even after correction for population phylogenetic relatedness. CONCLUSIONS: Differences in degrees of sexual dimorphism in study populations cannot be explained by allometry alone, but rather they result from a complex interplay of various factors and pressures, including phylogenetic origin, environmental conditions, and cultural norms.