No luck with Match.com or EHarmony? Online daters now have a new way to screen potential dates. Two companies offer genetic analysis that purports to find your perfect love match based in part on the smell of his or her sweat.

The genetic tests for both companies--ScientificMatch, based in Naples, FL, and GenePartner, based in Zurich, Switzerland--are based on the same study, performed more than a decade ago in Switzerland. Women were asked to rate the odor of men's sweaty T-shirts, and then both sexes were tested for the genotype of several genes within the major histocompatibility complex (MHC), a family of genes that is crucial for immune function. Women were more likely to prefer the sweaty smells of men whose MHC genes were most different from their own.

While it sounds bizarre, the finding does have a potential evolutionary explanation. According to an article from the Economist,

The children of couples with a wide range of MHC genes, and thus of immune responses, will be better protected from disease. . . . 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.

Does it really work for finding a date? Probably not. Subconscious feelings about a person's smell likely make only a minor contribution to each person's attractiveness equation.