The XX Factor: What women really think.

Are Birth Control Pills Ruining Your Love Life?

Has anyone been reading about this new U.K. study examining how the birth control pill affects women's choice of sexual partners? As one CBS headline crudely puts it, women on the pill allegedly choose "the wrong partner." That's because, as the authors of the study argue, women NOT on the pill are generally "attracted to men whose genetic makeup differs from their own" which "increases the chances for a healthy pregnancy and a healthy baby," as CBS put it. But women on the pill seem to choose partners who are genetically similar to themselves. I can't quite tell how they've determined this, but it has to do with something called MHC genes, which affect immune responses, and smelling T-shirts.  As CBS puts it: "In laboratory studies, women who sniff men's sweaty T-shirts find them more attractive when they come from men whose MHC genes don't match  theirs. It's not that certain MHC genes smell better to women -- it's the difference that counts."

On the pill, however, this seems to change, and it has, according to a number of scientists, a lot of implications for relationships going forward, because apparently women who are with men who have similar genetic material get dissatisfed quickly and search for new sex partners. (It's not your hair, honey, or the fact that you don't do the dishes, it's your MHC genes.) But do these kind of studies really tell us very much? Are our sex and romantic lives really so genetically deterministic that we can make predictions based on smelling a man's T-shirt? (God, that would have saved a lot of novelists some trouble.) I'd love to know what some of our more scientifically trained XXFactor bloggers have to say, because the study and the conclusions being drawn raised all sorts of questions for me. It's times like these when you wish more journalists understood biology, because the pieces I've read on this story seem, in general, very crude.