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That's the bizarre side effect of the pill being reported by researchers from the University of Newcastle in England, who say it all comes down to body odor. In the mating dance we all do--on the pill or not--it's a woman's flowery fragrance or a guy's musky, sweaty smell that attracts the opposite sex, sending out aromatic molecules that indicate genetic compatibility, reports LiveScience.com. Put simply, the best mate is someone who smells different than you. But the pill seems to make this olfactory mating sense go awry, so women who are taking it prefer men who have matching odors or in science-speak have the same major histocompatibility complex (MHC) genes. Why does this matter? When people with different MHC genes have children, those kids have better immune systems that can recognize a broader range of foreign cells. Previous research has also shown that couples who have dissimilar MHC genes are more satisfied and more likely to be faithful to a mate, reports LiveScience.com. The problem is that the opposite is also true for couples who have matching MHC genes. The kids' immune systems are weaker and Mom and Dad show less satisfaction and more wandering eyes. "Not only could MHC-similarity in couples lead to fertility problems," lead researcher and evolutionary psychologist Stewart Craig Roberts told LiveScience.com, "but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odor perception plays a significant role in maintaining attraction to partners." The study: About 100 women, ages 18 to 35, participated in the University of Newcastle study. They chose which of six male body-odor samples they preferred. This test was done at the beginning of the study when none of the women were taking the pill and three months later after 40 of the women had been taking the pill for more than two months. The results: The women who didn't take the pill had no significant preference for similar or dissimilar MHC odors, but the odor preferences changed for the women who started taking birth control. These women were far more likely than non-pill users to prefer MHC-similar odors, reports LiveScience.com. "The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odors," Roberts said. Why does this happen? Because birth control pills make the body think it's pregnant, hormonally speaking at least, a woman on the pill has no biological reason to seek out a mate--even though that's not really true. "When women are pregnant there's no selection pressure, evolutionarily speaking, for having a preference for genetically dissimilar odors," Roberts told LiveScience.com. "And if there is any pressure at all it would be towards relatives, who would be more genetically similar, because the relatives would help those individuals rear the baby. The pill is in effect mirroring a natural shift but at an inappropriate time." The study findings have been published in the journal Proceedings of the Royal Society B: Biological Sciences. --From the Editors at Netscape | |||||||||||||||
Single women who take birth control pills might want to be wary about the men they date. Why? It appears the pill may cause women to choose bad mates.
