When it comes to our social networks, it seems that birds of a feather flock together.
Everyone knows that we tend to choose friends who are similar to us. But just how similar are we? New research suggests that people who are friends are as genetically alike as fourth cousins.
“Normally, fourth cousins share a great, great, great grandparent in common,” said James Fowler, professor of medical genetics and political science at the University of California, San Diego. “We found that among friends who don’t share that kind of ancestor in common, they’re still genetically similar because they tend to choose friends who have similar traits.”
It appears that people genetically resemble their friends more than they do strangers in the same population.
The study examined over a million markers of gene variation among nearly 2,000 subjects. From there, researchers analyzed the DNA of pairs of friends versus pairs of strangers.
“I was surprised by how much of the genome we found in common,” said Fowler, who co-authored the study. “One of the things that we’re really interested in is where does this tendency come from?”
One of the things Fowler and his team found was that the genes we share most in common with our friends are also the genes that are evolving the fastest, which may help explain why this tendency is so universal. After all, if you’re the first person to speak language, it’s only beneficial if you have a friend to talk to.
“You need to surround yourself with the same kinds of genes that give you the same kinds of traits,” said Fowler. “We think there are a lot of these kinds of traits that are based on our social networks rather than just being traits that help us individually.”
According to Fowler, human beings are unique as a species in that we spend more time interacting with people who are not our mates and not our kin. Other social species, like ants or dolphins, tend to surround themselves with only family members.
In other words, we have friends.
“What our research suggests is that that property of being human, of having friends, may have turbo-charged evolution, and may be accelerating the rate that we as a species evolve,” said Fowler.
By Marianne Hayes