Sharing Genes with Friends 

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By Susan Heckler

Scientists from University of California-San Diego and Yale have found that we are genetically similar to our friends more so than we are to strangers of the same population. Their findings suggest that our social networks also play an important role in human evolution, in addition to our physical and biological environment. In fact, researchers say our friends are as “related”—genetically speaking—as fourth cousins.

The claim that friends wear the same genes was the subject of a recent article in Discover magazine. The research focused on 1,932 subjects who participated in a 1948 Framingham Heart Study,  which produced one of the largest datasets of both genetic information and details of social relationships. Additionally, they used the data base of the National Longitudinal Study of Adolescent Health.  According to Discover, “A vast majority of people in the Farmingham study had European origins, which ensured both friends and strangers were drawn from the same population.” Nearly 1.5 million markers of gene variations and compared pairs of unrelated friends against pairs of unrelated strangers were analyzed.

Friends shared enough genes to develop a ‘friendship score,’ which was used as a predictor of friendships.  We share 1% of our genes with our friends, giving researchers the same confidence level of results as predicting obesity.

Friends were most similar in genes affecting the sense of smell, and most different when it came to genes that affect immunity against various diseases. In the Proceedings of the National Academy of Sciences, “friends may be a kind of ‘functional kin.’” This leans toward the theory that we tend to befriend people who not only look similar to us but also have certain genetic similarities to us.

An interesting fact is that humans are the only species in the animal kingdom that actually have friends, or long term connections. The researchers believe that the findings suggest that choosing friends who share similar genes is a behavior that may have contributed to human evolution. “We live in a sea of genes,” says lead author James Fowler, professor of medical genetics and political science at the University of California-San Diego. “What happens to us may not depend only on our genes but on the genes of our friends.”

In a Time Magazine article they state, “The first gene, DRD2, is involved in producing a type of dopamine receptor, and the researchers report that people with a variant linked with increased risk for alcoholism were more likely to be friends with each other. Those with the variant were 10% more likely to be pals than would be expected by chance. Since most of the participants in the adolescent database were just 14 at the time they were studied, it’s not likely that, for example, they met each other in bars, which might otherwise explain the connection. Although DRD2 has been the subject of other conflicting studies on its potential relationship to impulsivity or risk for ADHD, the alcoholism finding has been repeatedly replicated.”

Maybe the Beatles were on to something when they wrote, “I get by with a little help from my friends?”