Smelly Science?

A new study from Craig Roberts in the journal Proceedings of the Royal Society B: Biological Sciences notes that birth control pills could cause a woman to choose the wrong mate.

From an article byJeanna Bryner at LifeScience:

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.

MHC genes churn out substances that tell the body whether a cell is a native or an invader. When individuals with different MHC genes mate, their offspring's immune systems can recognize a broader range of foreign cells, making them more fit.

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.

"The results showed that the preferences of women who began using the contraceptive pill shifted towards men with genetically similar odors," Roberts said.

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The abstract and link to the journal article is here.

A few thoughts:

1. This explains my wife’s disinterest after having kids!

2. There was no placebo group used in this study, always a red flag in my books, especially when one could have easily been done.

3. There is no data to suggest that scent plays a primary role in choosing a mate in this testing group. Only MHC compatible or incompatible scents were tested, which is a far cry from the actual dating choices. That is, there are way too many other factors involved.

4. On the other hand, a new genetic/MHC compatibility internet dating service could be just around the corner for some enterprising person who reads this blog. eSmell.com anyone? Or perhaps a new cologne “infertile, for Men. By Calvin Klein”

5. If my understanding of genetics is correct, MHC is more compatible with first degree relatives. Don’t give your sister the pill.

6. Craig Roberts is the same researcher who determined that women prefer more "rugged" men during the fertile phases of their menstrual cycle (Abstract here). Then again, I'm not sure how much we can trust research from someone who can't spell "odor" correctly.