The Role of Sexual Autonomy in Evolution by Mate Choice

Abstract

The field of sexual selection is dominated by research in which natural selection on mating preferences is assumed. As a result, there has been no need to recognize any of the consequences of mate choice that can be independent of natural selection. One such consequence is the evolution of sexual autonomy- defined here as the capacity of an individual organism to pursue its mating preferences independent of sexual coercion from the opposite sex. Here, I propose that the concept of sexual autonomy was implicit in Darwin’s work on mate choice, as evidenced by early criticisms of sexual selection by Darwin’s’ contemporaries. Subsequently, Fisher, Lande, and Kirkpatrick provided models of the origin of sexual autonomy through mate choice. Here, I propose that sexual autonomy evolves via the indirect costs of sexual coercion, and can involve evolution of either resistance to coercion or new aesthetic preferences. I review two distinct examples of this phenomenon—antagonistic genital coevolution in waterfowl (Anatidae) and the evolution of bowerbird (Ptilonorhynchidae) architecture—both of which protect females from sexual coercion. Waterfowl vaginal complexity evolves as a mechanism of resistance to protect females from unwanted forced fertilization, and reinforces female capacity for autonomous mate choice. Bowerbird bowers evolve by female preference, and function to physically protect females from male sexual attack. Female preferences for bower architecture provide an aesthetic mechanism for reinforcing female sexual autonomy. Recognizing the evolution of female sexual autonomy provides a new avenue for investigating the evolution by the indirect benefits of mate choice.