Darwin's Legacy: An Evolutionary View of Women's Reproductive and Sexual Functioning
Harris, Amy L., Vitzthum, Virginia J., The Journal of Sex Research
Nothing in biology makes sense except in the light of evolution.
--Theodosius Dobzhansky (1973)
Worldwide celebrations in 2009 marking the 200th birthday of Charles Darwin and the 150th anniversary of the publication of On the Origin of Species rightly acknowledged the transformative impact of Darwin's work on a host of scholarly fields including, of course, biology. Nonetheless, the use of an evolutionary lens to understand variation in women's reproductive functioning is a relatively recent development, arguably beginning only about 40 years ago. Happily, human reproductive ecology has bloomed rapidly despite its late start, and nowadays scholars from the various disciplines that study human reproduction have begun to incorporate an evolutionary perspective and the methods of reproductive ecology into their work.
Darwin's legacy is not only a widespread recognition of the fact that organisms, including humans, have evolved. Darwin spent decades amassing and analyzing the evidence that gave credence to evolutionary theory, and many hold him in high regard as much for his empirical contributions as for his ideas. To avoid the trap of being nothing more than "wind sauce and air pudding," an evolutionary perspective on any aspect of an organism's biology and behavior must be grounded in both an explicit theoretical framework and rigorously collected empirical data. Sex researchers have also long held comparable views regarding the centrality of empiricism in their field (witness The Kinsey Institute and other centers). In the practice of science, data trumps theory (i.e., hypotheses must be tested with evidence). Hence, with an eye toward facilitating a productive exchange between sex researchers and reproductive ecologists, in this review we examine both the theoretical arguments and the currently available empirical evidence that inform an evolutionary view of women's reproductive and sexual functioning.
We begin with a brief history of the different scientific approaches to human reproduction and discuss the Flexible Response Model (FRM), an evolutionary model that helps to explain variation in women's reproductive functioning. Because it is often taken for granted that some specific aspect or another of reproductive functioning is "adaptive," we also note the strengths and limitations of different concepts of adaptation. A third signature feature of Darwin's legacy is the recognition that variation among individuals is natural rather than aberrant. This evolutionary view contrasts starkly with platonic ideals and biomedical concepts of "normal" and "pathological." In keeping with this Darwinian insight, we next examine the substantial variability in ovarian functioning now known to occur temporally (i.e., from cycle to cycle within an individual), among women, and among populations, and consider the implications of this variability for conducting sex research. Within this section we also evaluate the relative merits of various biomarkers that serve as proxy measurements of a woman's reproductive and hormonal status. In the final section we apply perspectives and methods from reproductive ecology to help shed light on several contentious issues: the links between hormones and sexuality in premenopausal and perimenopausal women, the causes of premenstrual syndrome, and the existence (or not) of menstrual synchrony.
The breadth of sex research makes it impossible to be comprehensive in this single work, and not all questions within sex research are necessarily amenable to evolutionary approaches. As well, space and time precluded drawing more extensively than we did from the rich literature on nonhuman primates. Nor have we undertaken an in-depth critique of related work in evolutionary psychology, although we do draw attention to those methods and data presented herein that are directly relevant to critically evaluating published literature and informing future studies in that field. …