Using Darwin to find a date

ONE of life's little mysteries is why particular people fancy each other—or, rather, why they do not when on paper they ought to. One answer is that human consciousness, and thus human thought, is dominated by vision. Beauty is said to be in the eye of the beholder, regardless of the other senses. However, as the multi-billion-dollar perfume industry attests, beauty is in the nose of the beholder, too.

ScientificMatch.com, a Boston-based internet-dating site launched in December, was created to turn this insight into money. Its founder, an engineer (and self-confessed serial dater) called Eric Holzle is drawing on an observation made over a decade ago by Claus Wedekind, a researcher at the University of Bern, in Switzerland.

In his original study Dr Wedekind recruited female volunteers to sniff men's three-day-old T-shirts and rate them for attractiveness. He then analysed the men's and women's DNA, looking in particular at the genes that build a part of the immune system known as the major histocompatability complex (MHC). Dr Wedekind knew, from studies on mice, that besides fending off infection, the MHC has a role in sexual attractiveness. It changes odours in ways the mice can detect (with mice, the odours are in the urine), and that detection is translated into preferences for particular mates. What is true for mice is often true for men, so he had a punt on the idea that the MHC might affect the smell of human sweat, as well.

It did. Women preferred T-shirts from men whose MHC was most different from their own. What was more, women with similar MHCs favoured the use of similar commercial perfumes. This suggests that the role of such perfumes may be to flag up the underlying body scent rather than mask it, as a more traditional view of the aesthetics of body odour might suggest.

That makes evolutionary sense. The children of couples with a wide range of MHC genes, and thus of immune responses, will be better protected from disease. As the previous article suggests, that could be particularly important in a collaborative, group-living species such as humanity. Moreover, comparing MHCs could be a proxy for comparing kinship, and thus help to prevent inbreeding.

-How to find a mate