(Telegraph) Friends have closer DNA than strangers, scientists find
By Sarah Knapton, Science Correspondent 7:00PM BST 14 Jul 2014
Friends are as genetically similar as fourth cousins, a study by Yale and the University of California has found
Blood is supposed to be thicker than water, but a new study suggests that friends are as genetically close to us as members of our own family.
Researchers who compared the DNA of unrelated friends were intrigued to find they had the same genetic similarity as fourth cousins, or people who share great-great-great grandparents.
The finding remained even after controlling for ethnic, cultural and geographical bias.
“We are somehow, among a myriad of possibilities, managing to select, as friends, the people who resemble our kin,” said Nicholas Christakis, professor of sociology, evolutionary biology, and medicine at Yale.
The researchers looked at 1.5 million markers of gene variation and found that friends are most similar in genes affecting the sense of smell and least compatible in genes controlling the immune system.
Recent studies have found that people appear to choose partners based on differences in immunity.
It has been suggested that forming social groups with others who are able to withstand different pathogens reduces the spread of disease and increases the chances of survival.
“Looking across the whole genome we find that, on average, we are genetically similar to our friends,” said co-author James Fowler, professor of medical genetics at the University of California.
“We have more DNA in common with the people we pick as friends than we do with strangers in the same population.”