Masculine face, muscular body, deep voice and symmetry. These are features that typically trigger sexual desire in heterosexual women. But not when they’re pregnant. Sexual desire during pregnancy appears to be motivated more by a desire to ensure continued investment in the expected offspring than by any specific features of the woman’s sexual partner, according to a pair of Cal State Fullerton anthropologists.
Elizabeth Pillsworth, professor of anthropology, and alumna Jaclyn Magginetti ’08, ’12 (B.A., M.A. anthropology) are the authors of a new study on “Women’s Sexual Strategies in Pregnancy,” published in the journal of Evolution and Human Behavior.
Surveying 112 pregnant women in committed relationships, the researchers found that women who perceive possible threats to their relationship are most likely to experience sexual desire for their partners during pregnancy, and pregnant women who rate their partners as lower on investing qualities such as financial resources, responsibility and kindness are more likely to report feeling sexual desire for men other than their partners.
“In this study, we found that women’s sexual desires during pregnancy were related to their perceptions of their partners as reliable and investing fathers, but was not related to either trimester or their perceptions of their partners’ physical or sexual attractiveness,” explains Pillsworth.
“This is the first study that we are aware of to explore women’s sexuality during pregnancy from an explicitly adaptive perspective,” she continues. “Historically, pregnant women’s sexuality has been studied from a clinical perspective, focusing on description (e.g., do women generally experience an increase or decrease of sexual desire during pregnancy?) or treatment of pathologies.”
Furthermore, previous research has mostly focused on the correlation between hormonal changes during pregnancy and sexual desire, Pillsworth says, and “the results of these studies have been contradictory and largely uninformative about the social factors that affect sexual desire.”
Meanwhile, evolutionary research on human female sexuality has centered almost exclusively on sexual motives that are driven by the possibilities of conception, providing little insight into how evolution may have shaped nonconceptive sex, she says.
“Sexual behavior always entails costs — time, energy, infection risk, etc. — and females of most species consequently restrict sexual behavior to those times when they are likely to obtain reproductive benefits, either in terms of conception or offspring investment by males,” explains Pillsworth.
“Humans are exceptionally unrestricted in their sexual behavior, but we should still expect that women’s sexual desires and behaviors will also follow an evolutionary logic that would have resulted, on average, in reproductive benefits among ancestral women — and the results from our study support that.”
Pillsworth, who teaches such courses as “Anthropology of Sex and Gender” and “Medical Anthropology,” says the study can help people understand the evolutionary function of sexual desire at different times and in different contexts, and allow women to have a better understanding of their own bodies and emotions.
“Men’s and women’s sexual and romantic desires have been shaped by millennia of evolution that favored strategies resulting in reproductive success, but today’s living people have goals that are apart from those of natural selection,” she says.
“This research shifts the focus on women’s sexuality from one that perceives desire as a passive response to sexual stimuli to one that perceives desire as part of the active strategies that have evolved as part of human sexual psychology to increase women’s own reproductive success.”