A new direction in research on sexual selection in humans

Abstract

There are two distinct questions at the heart of the facial masculinity literature—the function of the trait, and women’s preferences for it. I argue that we should establish the former before we explain the latter. Women’s preferences for facial femininity indicate that we cannot presume attractiveness explains selection for secondary sexual traits like facial masculinity. A new direction in research on sexual selection in humans. This is a timely and much needed critical evaluation of the support for the immunocompetence hypothesis generally, and of the trade-off hypothesis specifically. There are 2 questions at the heart of this literature, and we have been led astray by asking only 1 of them. Facial masculinity is a secondary sexual trait, which means it evolved because it provided some advantage in mating competition (Andersson 1994). If we are to understand when and why women find masculinity attractive, our explanation ought to be informed by the function of the trait. Emphasizing the former question to answer the latter can lead to problems, as was made clear to me in the review article. In the section, “Female responses to masculinized stimuli may reflect preferences for competitive mates,” the authors must make their case for why an aggressiveness hypothesis can better account for women’s attraction to feminized faces than the trade-off hypothesis. And yet—men evolved masculine faces. Explaining women’s preferences for femininity cannot be the complete story, because they cannot explain selection for masculinity. This, of course, lends support for an aggressiveness hypothesis, which parsimoniously explains the existence of the trait as well as women’s aversion to it. Women’s preferences for facial femininity suggest that contest competition and female choice do not necessarily select for the same traits. Different sexual selection mechanisms indeed select for different kinds of traits, and can result in sexual selection for a variety of traits that are unattractive. Attractiveness research on secondary sexual traits should then begin not by explaining preferences, but by explaining the trait. To best understand when and why women find a secondary sexual trait attractive, we ought first to understand what the trait is for—because it may not be for attracting women. Accordingly, discovering which sexual selection mechanisms are responsible for men’s and women’s secondary sexual traits is of paramount importance for future research on sexual selection in humans (e.g., Puts 2010). This perspective predicts that if facial masculinity was selected for use in contest competition, women should find masculine mates attractive in contexts where contest competition predicts benefits to women, and either ignore it or find femininity attractive where women do not benefit from contest competition—and initial research suggests support for this hypothesis (Scott, Pound, Stephen, Clark, & Penton-Voak 2010; Snyder, Fessler, Tiokhin, Frederick, Lee, & Navarrete 2011; Stone 2011). The reflection prompted by this review presents an opportunity to clarify our questions— including explaining the trait before we explain preferences for it.