Friendships are down to genetics, says new study

How much choice do we really have when deciding on whom we make friends with? This was the question posed by a study published last week in the Proceedings of the National Academy of Science. In it, US teams at Harvard University and the University of California, San Diego, suggest there is strong evidence that genetics plays a substantial role in how popular we are.

The data was collected from the National Longitudinal Study of Adolescent Health, carried out by researchers at the University of North Carolina, Chapel Hill, US. The health and social behaviours of some 90,000 teenagers has been followed since 1994, and various trends have emerged.

The paper suggests that as much as 46 per cent of social variation seen between people could be hereditary. Although this seems intuitive, as genes conceivably determine how out-going or sympathetic a person is, it remains difficult to provide evidence for. 'No one has ever drawn the link between genes and social networking', says John Fowler, political scientist at the University of California, and first author on the paper. 'It suggests a whole new field of enquiry'.

Focusing on 552 pairs of twins, the two groups compared lists of friends between identical twins (who share the same genes) and same-sex fraternal twins (who do not). They found that genes are about 50 percent responsible for both our number of friends, and whether we prefer to belong to a number of different social groups, or to stick to a smaller number of close relationships. Such studies are very informative for wheedling out broad genetic correlations, as any difference between the two pairs might be due to their genes.

Speaking to ScientificAmerican.com, professor of Sociology at Harvard University and co-author of the paper Nicholas Christakis says: 'Your social position in a network is not purely of your own making. In a very deep sense, our social life is predestined. It's predestined genetically'. John Fowler added: 'Going forward, we are going to find that social networks are a critical conduit between our genes and important health outcomes'.