Wednesday, August 13, 2008

What Is That Smell?

Here we go again:

While several factors can send a woman swooning, including big brains and brawn, body odor can be critical in the final decision, the researchers say. That's because beneath a woman's flowery fragrance or a guy's musk the body sends out aromatic molecules that indicate genetic compatibility.

Major histocompatibility complex (MHC) genes are involved in immune response and other functions, and the best mates are those that have different MHC smells than you. The new study reveals, however, that when women are on the pill they prefer guys with matching MHC odors.

Best mates? What sort of research is this based on? What is the frequency distribution of these smells in the general population?

And do the guys prefer different MHC smells from their own? Do the parents apply these rules in societies where marriages are arranged? What about those cultures which favored cousin marriages? How often have women had the chance to pick their own mates?

Here's more on the study:

Past studies have suggested couples with dissimilar MHC genes are more satisfied and more likely to be faithful to a mate. And the opposite is also true with matchng-MHC couples showing less satisfaction and more wandering eyes.

"Not only could MHC-similarity in couples lead to fertility problems," said lead researcher Stewart Craig Roberts, an evolutionary psychologist at the University of Newcastle in England, "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."

Sexy scents

The study involved about 100 women, aged 18 to 35, who chose which of six male body-odor samples they preferred. They were tested at the start of the study when none of the participants were taking contraceptive pills and three months later after 40 of the women had started taking the pill more than two months prior.

For the non-pill users, results didn't show a significant preference for similar or dissimilar MHC odors. When women started taking birth control, their odor preferences changed. These women were much more likely than non-pill users to prefer MHC-similar odors.

Well, it could be interesting that the smell preferences of some of the women on the pill changed. But note that the women not on the pill apparently didn't express a preference for dissimilar MHC odors. Doesn't that sorta affect the basic thesis and all the speculation that follows?

And what is "much more likely" in that study? How many of the pill users changed their preferences?

Pardon me for sounding suspicious, but it's hard to take the evidence of "past studies" completely seriously because those studies were in this same field of evolutionary psychology, looking for the same kind of stuff, and often popularized with the same extreme language.