Science tells us that humans have evolved over the years to make better decisions about whom to choose as a spouse, but a growing body of research suggests that women could undo all that evolution with a simple pill many are already taking.
Birth control pills, according to a review of the literature published today in the journal Trends in Ecology and Evolution, may alter the menstrual cycle in such a way that both women and men are affected in their appetites for the opposite sex.
But researchers caution it is too early to draw conclusions about the effects of the pill, and some even doubt if science could ever answer how much hormones dictate human attraction.
"While the general trend certainly points to the direction that the pill might indeed affect mate preferences in both sexes in a very intriguing way, we badly need further studies experimentally testing these effects," said Virpi Lummaa, a Royal Society University research fellow at the University of Sheffield in the United Kingdom and one of the review authors. "So, at this point, I wouldn't like to raise any concern among the pill users, just awareness that these type of effects might also be possible."
Over time, research has helped scientists hypothesize on how women might be attracted to different types of men at different points in their fertility cycle.
Around the time of ovulation, women would be more attracted to men who could provide good genetic material to their children. However, during periods when they were less fertile, they would be attracted primarily to men who would make good father figures and provide time and funding for offspring.
Men, meanwhile, have been found to be more attracted to women during the time of the month when they are most fertile. One study of exotic dancers published last year suggested that those who were not on the pill would see a rise in their tips around the time they reached peak fertility.
Research has suggested this to be the case, in part because when women were on the pill, the fluctuations in attraction do not swing as wildly, and exotic dancers who had been using birth control did not see significant variation in their tips as the month progressed.
But even if this hypothesis becomes a well-evidenced theory, it still may not mean women should go off the pill.
"We have to weigh the benefits as well as the costs," said Dustin Penn, director and senior scientist for the Konrad Lorenz Institute for Ethology in Vienna. "If it turns out to be true that the pill alters [women's] mating preferences. … They may be willing to accept those consequences given the benefits that they enjoy from the pill."
It is similar, he said, to the case of a medication that might reduce symptoms but prolong the illness itself slightly.
"We might choose to be sick another day because we don't want to feel bad," said Penn.
Dr. Karen Boyle, a fertility expert at the Greater Baltimore Medical Center, said doctors are pretty clear about what the pill can do to a woman biologically.
"Some of the newer birth control pills, the ones that have different hormone combinations that make menstrual cycles disappear, have been known to change the moodiness with the cycle," said Boyle. "The pill is also protective against ovarian and endometrial cancer."