Friends connect on a genetic level

Groups of friends show genetic similarity, according to a study that surveyed variation in two out of six genes sampled among friends and strangers. For some geneticists, the conclusion is difficult to believe, because the scientists have not analysed enough genes to be sure that other explanations are impossible.

James Fowler, a social scientist at the University of California, looked at the data on six genes from about 5,000 individuals, and recorded the variation at one specific point, or single nucleotide polymorphism (SNP), in each gene, and compared this between friends and non-friends.

After investigating genetic similarity due to sex, age, race or common ancestry, friends still used to have the same SNP at one position in a gene called DRD2. Friends also showed more variation at one position in the gene CYP2A6 than non-friends.

The ultimate function of DRD2 or CYP2A6 is not clear. But the authors point out that previous studies have associated both genes -controversially- with social behaviour: DRD2 with alcoholism and CYP2A6 with 'openness'. There might be an evolutionary benefit to having friends with compatible genes, even if you don't have children with them. For example, if people who are naturally less susceptible to bacterial infection meet together, their collective health as a group multiplies because the bacteria have no place to live in.

But not everyone is convinced. Because most genes have modest effects on behaviour or health, many scientists think that thousands of SNPs -not only six- need to be analysed before a correlation can be confidently made. 

Adapted from an article by Amy Maxmen in Nature News. Picture by Nana Taimour.