Self-reported aggressiveness does not follow facial masculinization in diverse South Asian populations

It has been suggested that sexually dimorphic facial traits are related to competitive behavior and aggression, but empirical evidence remains inconsistent and is based on a small number of populations and culturally homogeneous samples. We have combined geometric morphometric analyses with hierarchical Bayesian modeling of sixteen culturally and geographically diverse but understudied ethnic groups in order to test whether self-reported aggression covaries with facial sexual shape dimorphism within and between populations. Across populations, we found no consistent association between the individual level of facial sexual dimorphism and self-reported aggression in either sex. Although populations did differ in mean aggression levels, mean self-reported aggression covaried neither with the magnitude of sexual dimorphism nor with overall facial masculinization. Finally, sex differences in self-reported aggression did not reflect morphological sex differences. These findings challenge the generalizability of claims that aggression is encoded in the sexually dimorphic facial structure.