Friends Are More Similar Genetically Than Strangers, Study Says

From TIME - January 12, 2018

You may have more in common with your friends than you think, according to a new study published in Proceedings of the National Academy of Sciences. Your genes may be similar, too.

Past research has suggested that people tend to be somewhat genetically similar to their spouses and adult friends, likely because humans naturally gravitate toward people with whom they have something in common. But how and why does this subconscious sorting happen? Researchers from Stanford, Duke and the University of WisconsinMadison studied 5,000 pairs of adolescent friends using data from Add Health, a long-term study of people who were in grades seven through 12 during the 1994-1995 school year. They ran a number of genetic comparisons, seeking to learn more about pairs of friends and schoolmates.

Overall, the researchers found that friends were more genetically similar than random pairs of people, and about two-thirds as similar as the average married couple. Study author Benjamin Domingue, an assistant professor at the Stanford Graduate School of Education, says this similarity is strong enough to detect, but not nearly on the same level as siblings, for example.

This effect may be due to a concept called social homophily, or the idea that individuals form bonds based on shared characteristics, many of which can be traced back to genetics.

But there may also be a second phenomenon at work, according to the paper: social structuring, or the idea that people are drawn to others in their own social environment, which may itself be partially shaped by genetics. For example, certain socially mediated traits, like educational attainment and body mass index, were particularly alike among friends, while those without a strong interpersonal dimensionsuch as heightwere less likely to match up, according to the paper.


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