Groups of friends show patterns of genetic similarity, according to a study published today in The Proceedings of the National Academy of Sciences1. The findings are based on patterns of variation in two out of six genes sampled among friends and strangers. But the claim is a hard sell for some geneticists, who say that the researchers have not analysed enough genes to rule out alternative explanations. The team, led by James Fowler, a social scientist at the University of California, San Diego, looked at the available data on six genes from roughly 5,000 individuals enrolled in unrelated studies, 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 controlling for genetic likeness due to sex, age, race or common ancestry, friends still tended to have the same SNP at one position in a gene encoding the dopamine D2 receptor, DRD2. Friends also showed more variation at one position in a cytochrome gene, CYP2A6, than non-friends. An 'opposites attract' phenomenon may account for the variation in CYP2A6 among friends, say the authors. This result indicates that genetic patterns aren't always the result of friends who connect through similar activities, such as running marathons or playing musical instruments.