Biologists James Fowler of the University of California, San Diego, and Yale University’s Nicholas Christakis have made the claims.
NPR states that the researchers base their findings on a study of the genetic differences among nearly 2,000 people. The data were collected as part of the
Framingham Heart Study.The Framingham Heart Study is a long-term, ongoing cardiovascular study on residents of the town of Framingham, Massachusetts. The study began in 1948 with 5,209 adult subjects from Framingham, and is now on its third generation of participants.
The researchers, as the
BBC has reported, indicate that they found that friends shared about 0.1 percent more DNA than the average stranger; this is said to be a level of genetic similarity expected among fourth cousins.
Talking to the BBC, Christakis is quoted as saying: "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."
However, according to
The Scientist, some biologists are skeptical about the duo’s conclusions, arguing that some important factors — such as ethnicity and education level, which can lead to population stratification that makes two people more likely to meet and become friends — were not controlled for.
The conclusion is that friends tend to have a slightly higher kinship coefficient than strangers. The findings have
been reported to the journal
PNAS, in a paper titled "Friendship and natural selection."
