UCSD research finds genetic basis of friendships

When it comes to friendship, do opposites attract? Or are we more like our friends than we think? According to recent studies done by researchers at both UCSD and Yale, unrelated friends have a genetic makeup as similar as those whose great grandparents have the same grandparents. That relationship is described as fourth cousins, and amounts to an exact similarity of one percent of a persons genes. That 1% is a non-trivial correspondence in the eyes of geneticists. The conclusions seem amazing considering the fact that few of us would even know that someone is a fourth cousin to us, and yet many of our friends are as genetically similar to us as that distant relative.

James Fowler, professor of both political science and genetics at the University of California San Diego, and Nicholas Christakis, from Yale University in Connecticut, have published the results of their research in the Proceedings of the National Academy of Sciences.

For this observation, data of more than a million genetic markers were compared from participants in the Framingham Heart Study. That study contains the most genome information coupled with relationship specifics of any study available to the scientists.

More than 1,900 people were part of the study. Both their gene sequence and their network of friends were compared. No relatives going back seven generations or those married to each other were compared. Each pair of two friends were compared to pairs of strangers. The friends shared more genes in common than the strangers, seemingly concentrated in the genes related to the sense of smell.

The question of what mechanism, conscious or otherwise, can be being used to pick the closer genetic matches as friends remains unexplained. The outcome suggests reproductive and life span-lengthening advantages may result from having closer genetic matches as part of an individual’s  normal social network.

Funding for this study came from monies granted by both the National Institute for General Medical Sciences and the National Institute on Aging.