The implications of using hormonal birth control for human evolution.
Sheer Birnbaum & Tsachi Ein-Dor & Gurit E. Birnbaum
Abstract
Resistance to disease is greater for offspring if the parents have dissimilar immune systems, as their pathogen-detection ability is enhanced. Accordingly, women evolved to be sexually attracted to men with a dissimilar immune system, primarily during high-fertility cycle phases. Contraceptive pills, however, reverse women’ s preferences, leading them to be attracted to men with a similar immune system. In the present study (N =192), we compared the health of children born to parents who met while the mother was on the pill with that of children whose parents met when the mother was not on the pill. Results confirmed our predictions, indicating that children to mothers who were on the pill are more infection-prone, require more medical care, suffer from a higher frequency of common sicknesses, and are perceived as generally less healthy than children whose parents met on non-pill circumstances. Results are discussed in light of the current antibiotic world crisis.
People often use the expression “it smells funny to me.” Research has recently indicated that when it comes to romantic partners, people should indeed follow their nose: the more they like their partner’s body odor, the better the genetic fit is with respect to immune system benefits for potential children (Roberts et al. 2013). Unfortunately, the commonly used contraceptive pills may cancel out these potential benefits. When women use contraceptive pills, which imitate a state of pregnancy (Alvergne and Lummaa 2010), their natural odor preference for good-fitting romantic partners is reversed, such that they switch to preferring the odor of poorly fitting partners (Wedekind and Füri 1997; Wedekind et al. 1995). To date, it is still unclear whether this shift in mate preference affects the health of children born to couples who have met while the woman was on pills. In the present study, we examined this possibility by comparing the health of children born to parents who met while the mother was on contraceptive pills with the health of those whose mother was not on pills.
Fertility Status and Women’s Mate Preferences
When choosing a partner to have children with, it is only natural to desire “Prince Charming” or “Cinderella,” who may pass on their beneficial genetic qualities to future offspring. Given that better genes increase the offspring’ s survival and reproduction chances, theories suggest that mechanisms that detect “genetic quality” should have evolved to lead people to be sexually attracted to “knights in shining genes” (Bertram et al. 2016; Neff and Pitcher 2005). Several studies have indeed shown that during the fertile phase of the menstrual cycle, women prefer men with masculine faces, bodies, and voice (Feinberg et al. 2006; Frost 1994; Johnston et al. 2001; Penton-Voak and Perrett 2000; Penton-Voak et al. 1999; Puts 2005), which were theorized to indicate high quality genotype. Other studies, however, have indicated that “good genes” or “complementary genes” explain only a small portion of the variance in mate choice (Bertram et al. 2016; Neff and Pitcher 2005).
