An Empirical Investigation on the Sexual Selection Hypothesis of Human Phenotypic Diversity: A Test in Okinawa and Mainland Japan

Abstract

Sexual selection may have played a role in the formation and maintenance of phenotypic diversity among human populations. A theoretical study has shown that phenotypic diversification between neighboring populations connected by gene flow can occur if individuals have a mating preference for typical characteristics of their population (i.e., own-group preference), or if preferences are culturally transmitted only between the members of the same population (i.e., model-dependent mate-choice copying). To date, however, empirical investigation is lacking on the presence or absence of own-group preference and model-dependent mate-choice copying in neighboring populations exhibiting phenotypic differentiation. Here we report the results of an experiment on preference for faces in Okinawa Islanders and Mainland Japanese as an example of such populations. It was suggested that female Okinawa Islanders tend to prefer male faces of their own population to those of Mainland Japanese, and male Okinawa Islanders’ evaluation of faces is affected more by members of their own population than those of the other. These findings support the argument that the phenotypic difference between Okinawa Islanders and Mainland Japanese may be partially explicable by sexual selection.