Gene research finds opposites do attract

A comparative survey of couples suggests people are more attracted to those who have very different immunity genes from their own, even though they are not aware of it.

The genes in question play a major role in the immune system's ability to fight infections, but they are also thought to leave a lingering trace in the scent of people's body odour.

The scientist who led the study believes humans have evolved to sniff out partners who have different immunity genes because they tend to produce healthier children with stronger immune systems.

Bicalho's team looked at a group of genes known as the major histocompatibility complex (MHC), and noted down how much the genes varied between 90 married couples and 152 fictitious couples paired up at random by a computer. "But we found that the real partners had significantly more MHC dissimilarities than we could have expected to find simply by chance."

http://www.guardian.co.uk/science/2009/may/24/genes-human-attraction