An Evolutionary Functional Analysis of the Hormonal Predictors of Women’s Sexual Motivation

Abstract

What is the evolved function of women's sexual motivation? Recent research suggests that low sexual desire is a common condition among women, with rates of occurrence in the 20-40% range even among premenopausal women. The medical and scientific literatures have often treated low desire as a clinical disorder, with hypoactive sexual desire disorder codified as a recognized condition in the DSM-IV (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association 2000). An important question from a functional perspective, however, is whether low desire is a disorder in the sense of brain mechanisms failing to operate as designed, or simply with respect to desired outcomes. It is not clear, for instance, that fairly constant, uninterrupted desire would have promoted women's reproductive success on average over the course of human evolution. Understanding both between-women and within-woman variance in desire would seem to require knowledge of the functional design of the brain mechanisms that regulate sexual motivation. Surprisingly, this issue of functional design has been largely ignored in both the medical and scientific literatures on human sexuality. This chapter will analyze women's sexual motivation from a functional perspective, with specific emphasis on the role of hormonal signals in the regulation of desire. The chapter will also take a comparative approach to understanding women's sexual motivation. The physiology of the human menstrual cycle exhibits extensive parallels to that observed in the cycles of nonhuman primates, and broader homologies between human and nonhuman motivational systems make it reasonable to suppose that the mechanisms that regulate human sexual motivation will be variations on designs found in nonhuman species. This comparative perspective may help frame the issue of functional design in ways that may be obscured in the extant medical literature on human sexuality. As reviewed below, for instance, most nonhuman mammalian females are only sexually receptive on days of the estrous cycle when conception is possible, and thus by comparison the relevant functional question regarding women's sexuality is not why desire is so low but instead why it appears to be so much more frequent than in other species. (PsycINFO Database Record (c) 2016 APA, all rights reserved)