Does your DNA determine how many friends you have on Facebook?

"Always the last one picked for kickball? Never get invites to the hottest parties? Blame Mom and Dad.

That's right, a new study says genes may influence whether or not you're popular. But DNA, or genetic material, shapes more than popularity, according to the research published today in the Proceedings of the National Academy of Sciences. It may also play a role in the number of friends we have—and whether we're integral or insignificant members of a social group.

Researchers from Harvard University and the University of California, San Diego, found that genes may be responsible for 46 percent of the variation (or difference) in how popular we are versus other people. Genetics exerts a similar effect on people's varying degrees of connectivity (for example, one person might know many of their friends' pals, but another person may not know any of their friends' other buddies.) And DNA has a significant, but lesser influence, on the difference between where one or another of us is located in a social network.

The scientists based their findings on data from the National Longitudinal Study of Adolescent Health, a study by the University of North Carolina at Chapel Hill of the influence of health on the social behavior of some 90,000 teens who researchers have been following since 1994. Using information on 552 pairs of twins in the study, the Harvard and U.C. San Diego researchers compared the lists of friends of identical twins with the social circles of same-sex fraternal twins. The networks described by the identical twins resembled one another more than those of the same-sex fraternal twins, suggesting a genetic influence on how people network socially. Twin study designs presume that if identical twins resemble each other more on some trait than fraternal twins do, then genes help explain that trait.

'Your social position in a network is not purely of your own making,' study co-author Nicholas Christakis, a professor of sociology at Harvard University, tells ScientificAmerican.com. 'In a very deep sense, our social life is predestined. It's predestined genetically.

'It's not the only explanation,' he adds. 'But there is a discernible and substantial role of genes in your social network position.'

The study didn’t sort out which genes are enhancing or ruining our social lives. Michigan State University research published last year showed that a mutation in the serotonin receptor gene 5-HT2A was linked to variation in popularity. (Serotonin is a brain chemical that regulates mood, anxiety, depression, sleep and sexuality.) The new study examines the genetics of popularity with a wider lens, examining how much DNA may shape the way we socialize.

There may be evolutionary reasons for the variations in our social connectedness, Christakis says. While it may be advantageous to be in the center of a group when rumors are circulating, he says, you're better off being on its fringes if a disease—not gossip—is spreading. But the study didn’t explore who might benefit from being popular—and who may be lucky to be on the outs.

'We're a social species. We shouldn’t be surprised that some aspects of how we're social depends on genetics,' Christakis says. 'Just like other aspects of your personality of how assertive you are, how risk-averse you are, so does your predilection for having particular kinds of social network architectures' depend on genetics."

(credit: Scientific American)

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