Two new studies in the November issue of the journal Evolution and Human Behavior find that women get a little wilder during their most fertile days of the month. One study found that ovulating women are more open to the idea of hooking up with a stranger or acquaintance, while the other study found that women with less masculine-looking partners are more likely to lust after men with “masculine” traits–like strong, square jaws–than women with partners already possessing those traits.
In the past, most research on the menstrual cycle focused on premenstrual syndrome (PMS), but these new studies are two of more than twenty focusing on behavioral changes brought about by ovulation. Researchers in evolutionary biology have taken it for granted that ovulation is of slight significance since humans have deviated from the typical estrus cycle (heat) of mammals, and can be up for sex anytime of the month.
This, however, is just a theory, and a wrong one at that. For instance, men can tell when a woman is ovulating, although they do so imperfectly. Some experts believe it’s through smell–of pheromones, excreted chemicals that triggers a social response in members of the same species–but this is just a hypothesis. Several studies, however, have found that women report that their men become more attentive and jealous around fertile days. One study, in fact, found that when women were fertile, their male partners saw other men as a greater threat.
Further, women do have a sort-of “heat” phase, yet instead of simply being more receptive to sex, they want it for different reasons. Consider this phase a lust-cycle, where women want sex for sex’s sake and not for intimacy, which might be more the reason outside of the cycle.
The second study of the pair looked at womens’ phenotypic preference for masculine traits during fertile periods. Several previous studies had found that, when ovulating, women tended to go for more masculine-looking men. Masculine traits fertile women prefer are strong-jawed faces, muscular bodies, dominant behaviors, deep voices and tallness.
(Example of test picture to the left–women, which face do you prefer?)
In the latest study, researchers found that if a woman is partnered with a man without a masculine face, her eye is more likely to wander during her fertile days. Now this doesn’t mean she’ll necessarily act on her wandering eye, but she’ll likely look nonetheless. And other studies have shown that the hormonal fluctuations surrounding ovulation do change women’s attitudes and behavior. For instance, fertile women seem to be more open than non-fertile women to the idea of taking “sexual pleasures where [they] find them.” According to the authors of the study, women in ovulation are more likely to express interest in sleeping with an attractive stranger or someone they don’t care about. Just sex.
Women in ovulation also tried harder to look nice for pictures, according to a 2006 study, showing that the hormonal changes may also affect female decision making. An online shopping experiment reveals fertile women are also more likely to choose sexy clothes and accessories than women who weren’t fertile, according to the study published online in the Journal of Consumer Research in August. Finally, in a widely publicized study published in Evolution and Human Behavior in 2007, researchers found that ovulating strippers made an average of $30 more an hour than menstruating strippers and $15 more an hour than non-ovulating, non-menstruating strippers.
So to conclude, during fertile periods, women tend to be a bit friskier, make decisions about their attractiveness, look harder at masculine features, and be more likely to engage in casual sex. Why? To ensure the likelihood of fertilization and to increase the probability of finding successful genes, biologically speaking that is. I don’t know about you, but it sounds to me like the human female is as much a product of her biology as a man is. Cool, huh?