Abstract

Sexual selection was initially introduced by Darwin to explain the evolution of extravagant secondary sexual characters which appear useless in the struggle for existence, like the peacock’s tail. It has become a major research focus in modern organismal biology, providing an evolutionary framework to understand sex differences. However, the study of sexual selection has been heavily biased towards males, and we know comparatively little in females. Today I will talk about one of the most striking examples of sexual selection in females: the perineal swellings borne by female primates, including chimpanzees. Ornaments are usually found in males, and the evolution of sexual swellings has thus been a long puzzle for evolutionary biologists. I will present empirical tests investigating the evolutionary significance of sexual swellings in wild baboons to show that reproductive competition among females can be intense in promiscuous primate societies, and that mechanisms of sexual selection are qualitatively similar in males and females.