MHC and sexual selection
It has been suggested that MHC plays a role in the selection of potential mates, via olfaction. MHC genes make molecules that enable the immune system to recognise invaders; generally, the more diverse the MHC genes of the parents, the stronger the immune system of the offspring. It would obviously be beneficial, therefore, to have evolved systems of recognizing individuals with different MHC genes and preferentially selecting them to breed with.
Yamazaki et al. (1976) showed this to be the case for male mice, who show such a preference for females of different MHC. Similar results have been obtained with fish.[4]
In 1995, Swiss biologist Claus Wedekind determined MHC-dissimilar mate selection tendencies in humans. In the experiment, a group of female college students smelled t-shirts that had been worn by male students for two nights, without deodorant, cologne or scented soaps. Overwhelmingly, the women preferred the odors of men with dissimilar MHCs to their own. However, their preference was reversed if they were taking oral contraceptives.[5] The hypothesis is that MHCs affect mate choice and that oral contraceptives can interfere with this. A study in 2005 on 58 test subjects confirmed the second part - taking oral contraceptives made women prefer men with MHCs similar to their own. [6]. However, without oral contraceptives, women had no particular preference, contradicting the earlier finding[7]. However, another study in 2002 showed results consistent with Wedekind's--paternally inherited HLA-associated odors influence odor preference and may serve as social cues.[8].
In 2008, Peter Donnelly and colleagues showed that MHC is related to mating choice in European Americans but not in Africans using HapMap II dataset.
