The idea that we choose our mates based on their genes isn't news, but researchers in San Diego now have evidence that we might also be choosing our friends by their genetic endowment as well.
"We're asking a much broader question -- how and why do we make friends," says James Fowler, who studies social networks at the University of California, San Diego and first author on the paper published in this week's edition of the journal Proceedings of the National Academy of Sciences. The researchers looked at six genotypes from the National Longitudinal Study of Adolescent Health to test for genetic similarity between friends. They found that when they mapped friendship networks, some of the genotypes clustered together.
In the case of the gene DRD2, which is associated with drinking behavior, friends were more likely to have friends who shared the gene. Another, CYP2A6, was linked to the trait of 'openness' in one paper and is also linked to the ability to process foreign substances. For an unknown reason, some friendship groups tended to avoid it.
(Elizabeth Wiese. Genetics plays a role in who we choose as friends. USA Today. January 17, 20111.)