Opposites attract -- how genetics influences humans to choose their mates

May 25, 2009

New light has been thrown on how humans choose their partners, a scientist will tell the annual conference of the European Society of Human Genetics today. Professor Maria da Graça Bicalho, head of the Immunogenetics and Histocompatibility Laboratory at the University of Parana, Brazil, says that her research had shown that people with diverse major histocompatibility complexes (MHCs) were more likely to choose each other as mates than those whose MHCs were similar, and that this was likely to be an evolutionary strategy to ensure healthy reproduction.

Females' preference for MHC dissimilar mates has been shown in many vertebrate species, including humans, and it is also known that MHC influences mating selection by preferences for particular body odours. The Brazilian team has been working in this field since 1998, and decided to investigate mate selection in the Brazilian population, while trying to uncover the biological significance of MHC diversity.

The scientists studied MHC data from 90 , and compared them with 152 randomly-generated control couples. They counted the number of MHC dissimilarities among those who were real couples, and compared them with those in the randomly-generated 'virtual couples'. "If MHC genes did not influence mate selection", says Professor Bicalho, "we would have expected to see similar results from both sets of couples. But we found that the real partners had significantly more MHC dissimilarities than we could have expected to find simply by chance."

Within MHC-dissimilar couples the partners will be genetically different, and such a pattern of mate choice decreases the danger of endogamy (mating among relatives) and increases the genetic variability of offspring. Genetic variability is known to be an advantage for offspring, and the MHC effect could be an evolutionary strategy underlying incest avoidance in humans and also improving the efficiency of the immune system, the scientists say.

The MHC is a large genetic region situated on chromosome 6, and found in most vertebrates. It plays an important role in the immune system and also in reproductive success. Apart from being a large region, it is also an extraordinarily diverse one.

"Although it may be tempting to think that humans choose their partners because of their similarities", says Professor Bicalho, "our research has shown clearly that it is differences that make for successful reproduction, and that the subconscious drive to have healthy children is important when choosing a mate."

The scientists believe that their findings will help understanding of conception, fertility, and gestational failures. Research has already shown that with similar MHC genes had longer intervals between births, which could imply early, unperceived miscarriages. "We intend to follow up this work by looking at social and cultural influences as well as biological ones in mate choice, and relating these to the genetic diversity of the extended MHC region", says Professor Bicalho.

"We expect to find that cultural aspects play an important role in , and certainly do not subscribe to the theory that if a person bears a particular genetic variant it will determine his or her behaviour. But we also think that the unconscious evolutionary aspect of partner choice should not be overlooked. We believe our research shows that this has an important role to play in ensuring healthy reproduction, by helping to ensure that children are born with a strong better able to cope with infection."

Source: European Society of Human Genetics

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shawnfromnh
1 / 5 (1) May 25, 2009
Maybe these guys are not taking into account that this may be just a recent change brought on by the fact that for several hundred years incest has been illegal in most of the world. After that long it seems that a significant amount of people that were prone to incestuous behavior would have died out from not breeding because of social taboos. The ones that might have probably didn't and breed with ones that weren't prone to this behavior.

Basically this characteristic is man made caused by centuries of religious taboos and laws which breed out this characteristic which is not 100% natural.



I imagine there are parts of the world that are more primitive in their views that these results may be a lot different to actually more the opposite. It all matters the control group and if you have long time mating laws that is a huge control variable.
robbscholl
not rated yet May 25, 2009
In a culture where marriages are arranged by family would this study show the same results?
Arikin
not rated yet May 25, 2009
This is a well proven biological fact. Biological mechanisms don't just change on the whim of culture.

There have been many many blind tests of selection based on odor. Body odor is affected by each person's immune system make up. Everyone chooses an immune type that is different from their own. This gives the child a bigger variety and better chance of survival.

Besides, even when mate selection is forced you aren't accounting for everything. Such a couple may be less attracted to each other and therefor produce fewer offspring. Also, they may be more likely to cheat and produce offspring with others...

If you want to mention incest then please remember the royal families of Europe that married too close. Their offspring usually died of rare diseases before they could reproduce themselves. So same net affect or non-affect :-)