How do you choose your friends? A new study finds that many people unknowingly choose friends who have some DNA sequences in common with them. Researchers compared gene variation between nearly two thousand people who were not biologically related and found that friends had more gene variations in common than strangers.
Researcher Nicholas Christakis says, "Most people don't even know who their fourth cousins are, yet we are somehow, among a myriad of possibilities, managing to select as friends the people who resemble our kin." Christakis says it makes sense, because the usefulness of a speech gene, for example, would depend on whether a friend shared the same gene, so there's an advantage to people's genes evolving at the same rate as their friends.