examines the "sweaty T-shirt" experiment, which demonstrated that the sense of smell may have more to do with mate choice than scientists previously thought. Females sniffing the T-shirts recently worn by males favored the scent of those whose immune response genes were different from their own.

In it, men each wore the same T-shirt for two days. The shirts were then put into identical boxes. Various women were asked to smell the shirts, and to indicate to which shirts they were most sexually attracted. The results showed that women were most attracted to men with an MHC most dissimilar from their own.

Evidence that women prefer the odor of men who are genetically similar to themselves -- though not too similar -- has emerged from a study at the University of Chicago reported in today's issue of Nature Genetics.