We know that there are many genes in the MHC I and II regions and that they are highly polymorphic. Combinations of these genes and polymorphisms are important because they are related to the number of peptides that can be presented to t-cells.
It has been shown in fish (arctic charr) that they can discriminate between MHC identical siblings and siblings with different MHC genotypes (Olsen, et al, 1997). Fish chose swimming in water scented with a sibling who had the same MHC genotypes over water in siblings who did not. In mice it has been shown that MHC genes influence individual body odor in mice and that mice also prefer MHC-dissimilar mates (Chaix, et al, 2008).
In humans, there have also been studies looking at odor preference and MHC region, although there have been no studies that have linked odor preference and attraction. In several “sweaty t-shirt” experiments women were asked their preference to smells found on t-shirts that had been worn by males with different MHC genes. Females significantly preferred the odor of males with dissimilar MHC regions to their own. Another study looked at the genetic similarity at the MHC region between spouses, which included 30 European American couples from Utah and 30 African American couples in which there was found an association between mate selection and MHC dissimilarity in the European American couples(Chaix, et al, 2008).
So if you have problems in your relationships it may not be your fault!
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These kinds of studies are really interesting. In college I took an animal behavior class and we actually did the sweaty t-shirt experiment.. It got pretty gross! But it makes sense evolutionarily that animals (and people) would prefer mates that are genetically different. More variability, more chance for offspring to survive, and less chance of mating with related individuals (and thus expressing recessive alleles).
ReplyDeleteSo that's what she meant when she said "it's not me it's you"...=)
ReplyDelete.. Very interesting explaination .. Great idea for a successful dating service ... "Dude, can I borrow your gym T- shirt, I have a date tonight " :)
ReplyDeleteI've also been impressed by these "sweaty t-shirt" experiments. There was another one done where women preferred the scents of men with more symmetrical faces (picked out only by their scent) but ONLY around the time they were ovulating. If it wasn't that time, or if they were on birth control, there was not much of a pattern in which scents they chose.
ReplyDeleteI've also heard of women who have been on the pill and dating someone, suddenly go off the pill and suddenly can't stand how their man smells.
Sometimes I feel like we're just puppets in this game of sexual selection, no? :)
The smelly experiment might come down to pheromones, olfaction, and psychology. While humans don't have a dedicated vomeronasal organ I think the role of pheromones has still to be fully determined (I could be wrong though).
ReplyDeleteThe MHC region has been the focus of many autoimmune cohort studies where monozygotic twins have similar genotypes putting them at high risk for a given disease, but only one of the pair will develop it. This is one of the reasons environmental causes are being looked at so intensely. If autoimmune diseases are any clue, then it might be part encoded in use, but also our environment.