If you thought you could hide your body odor under a generous splash of aftershave, you're kidding yourself. Two scientists have uncovered evidence that people pick perfumes that reflect the genetic make-ups of their immune systems. Those, as has been known for some time, determine our scents.
Scents seem to influence sexual attraction in humans. Women prefer the smell of T-shirts worn by men whose major histocompatability complex genes--which encode the proteins that make up an important part of our immune system--are different from their own, and vice versa. It's a mystery how the status of our immunity genes shows up in our armpits, but the researcher who discovered the phenomenon, Claus Wedekind of the University of Berne, Switzerland, speculated that potential partners use the signal to assure that their children get a varied set of immunity genes, which may help them ward off diseases better.
Since infant health is critical for evolutionary success, Wedekind wondered whether people might have a subconscious tendency to pick scents that amplify their own eau d'immune. So Wedekind and his colleague Manfred Milinski followed their noses and examined artificial, rather than natural, scents. They asked 137 volunteers to rate sets of perfume ingredients, both for use on their partners ("would you like your partner to smell like that?") or on themselves ("would you like to smell like that yourself?"). These people, all students and lab assistants in the University of Berne, had participated in Wedekind's earlier experiments, so their immunity genes had already been typed.
Volunteers with similar immune systems tended to choose the same fragrances for themselves, but not for their partners, Wedekind and Milinski report in the March issue of Behavioral Ecology. The most logical explanation, according to the team: We use perfumes to amplify our own natural scents, perhaps to be able to signal our immune systems "from a longer distance," says Milinski, who is now at the Max Planck Institute for Limnology in Plön, Germany.
The study shows how important perfume can be, says Andreas Ziegler, an expert on the human sense of smell at Humboldt University in Berlin. Boosting one's odor will "enhance the chances to be guided to a partner with whom sex is not only pleasurable but also biologically useful," he says.