In a recent paper out in PLoS Genetics titled Is Mate Choice in Humans MHC-Dependent? (Chaix et al. 2008) the authors use genetic data to see if the MHC locus is more or less similar between spouses than the rest of the genome. Selection of mates on the basis of MHC locus differences is something that’s been shown in a bunch of animal studies, but it’s still unclear how it works in humans. You may have heard of the studies where women who smelled used men’s undershirts preferred the smell of men with different MHC loci, but some studies have provided contradictory results.
To briefly explain: Genes in the MHC locus are involved in recognizing pathogens. Therefore it is likely advantageous to have more differences between the two alleles at this loci to have a better chance of recognizing more pathogens. Several studies with different animal models have shown a preference for mates that have less similar MHC loci.
What Chaix et al. find is that among European Americans the MHC locus is less similar between spouses than the rest of the genome. Suggesting that we, like mice, prefer to mate with people that have different MHC loci from our own. Notably Chaix et al. don’t find this pattern at all in the Yoruban African samples they examine which makes for some interesting discussion about possible cultural influence or diversity issues. While I don’t know enough about population genetics to confidently say how strong their results are, they sound reasonable to me.
I love the the way people are increasingly using human genomic sequence data to piece apart issues of evolution and demographic history. I also love that this paper is short and well written enough for someone who knows little about population genetics (eg. me) to understand.
