A.K.A smelly t-shirt experiment revisited. These experiments basically ask women to evaluate the "sexiness" of a man's body odor. Turns out, women consistently rated odors of men with dissimilar MHC genes to be most attractive. Here is a link to some background info. Similar studies have been done in mice and other primates and show that all else being equal, there is a preference for MHC dissimilarity. Just like in humans, the mechanism for the detection of genotype is olfaction.. Cool stuff.

In a bit of a twist, UNM researchers recently repeated the "sweaty t-shirt" experiment, but asked different questions. Instead of attractiveness, they were interested in looking at sexual receptivity and rate of extra-pair-matings. Results of their findings are here.

The take-home message.. If you're partner doesn't find your B.O., attractive, chances are, they're likely to find someone else's whose is...