REGION — The crux of a good friendship is sharing, whether it be advice, common interests, clothes or genes. That’s right, good friends share some genetic similarities, according to a new study co-authored by James Fowler, a professor of medical genetics and political science at UCSD.
The study, which was published in the Proceedings of the National Academy of Sciences, found that many friends share a little less than one percent of genetic markers, which is comparable to being fourth cousins.
The similarities are not just based on appearance. Fowler and co-author Nicholas Christakis, who is a physician and social scientist at Yale University, found that friends share a similar sense of smell.
The study addresses the possibility that friends may be drawn to the same places, because of the shared sense. For example, a person who likes the smell of coffee is bound to hang around cafes, which may lead them to strike up friendships with fellow coffee-drinkers.
Another find in the study is that many people seek friends with opposite immunities. If one germ tends to make somebody sick, it’s likely that close friends will be immune. This has obvious advantages, evolutionarily speaking. If the findings are generalizable, friends would be able to care for each other without fear of getting sick.
However, the study has some limitations. The data set was not racially or geographically diverse. The data came from about 1,300 friendship pairs in Framingham, Mass., most of which were white, and many were of Italian descent.
“While we’ve found that this is true for this one well-studied group of people, we don’t know if the results can be generalized to other ethnic groups,” Fowler told the Washington Post. “My expectation is that it will, but we don’t know.”
If the findings are true, they have evolutionary significance because they show that humans seek out synergistic traits in their friends to help their success (or survival).
“Social networks are an important engine for human evolution,” Fowler said. “Our friends are sort of like family members. They’re functional kin.”