Social fit may be a matter of genes, study finds

It’s no surprise that there’s a gene in congeniality.

After all, how well you make friends obviously depends to some degree on heritable personality traits such as whether you are gregarious or shy.

But in a paper published in the online version of the Proceedings of the National Academy of Sciences yesterday, researchers at the University of California San Diego and Harvard Medical School say heredity also strongly influences whether your friends know each other, and it helps determine your standing in social networks.

“Basically, we think there’s a gene that causes some people to be more likely to introduce one friend to other friends, with the result being that some people create denser clusters of social networks around them than others do,” said Dr. Nicholas Christakis, a professor of medical sociology at Harvard.

Christakis was co-author of the paper with James Fowler, an associate professor of political science at UCSD, and Christopher Dawes, a graduate student at UCSD.

Think about it this way: Some people are the life of the party, naturally drawing attention and crowds. Others tend to float on the periphery – social wallflowers, if you will. To a significant, measurable degree, the study finds, genetics put them in their places.

And you thought it was just about being a good conversationalist.

The role of genes in forming and configuring social networks is the latest eyebrow-raising discovery by Fowler and Christakis. Last year, they published a paper reporting that joy is infectious, spreading like a virus from one happy person to another. In another study, they found obesity to be similarly contagious. If your friend (or friend of a friend) put on weight, odds were you would, too. Likewise, the researchers found it is easier to quit smoking if people around you, known or unknown, are doing the same thing.

The latest study, however, focuses on a much less obvious component of social behavior: genes. The findings are based on data derived from a national study of 90,115 teenagers; in particular, 1,110 identical or fraternal twins.

Fowler, Dawes and Christakis compared the social networks of identical twins (who share 100 percent of their genes) with networks of fraternal twins, who share roughly half of the same genes. They found that the networks of identical twins were markedly more similar, indicating a stronger genetic influence.

Fowler conceded twin studies still have their skeptics, but he also noted that the methodology has been in use for more than 40 years, producing hundreds of published studies.

The scientists say the importance of genes in determining social position probably has evolutionary underpinnings, depending upon times and circumstances. If, for example, a deadly germ was spreading through a community, it could be beneficial to be on the social fringe and thus less likely to be exposed, Christakis said.

Conversely, people at the hub of social networks enjoy greater access to community resources, from information to food.

“There’s nothing intrinsically better about being in the middle or on the edge,” Christakis said. “If there were, if one kind of network was optimal, then nature would have already selected for it.”

Different kinds of networks provide different benefits at different times and under different conditions.

In an accompanying commentary, Matthew Jackson, an economist at Stanford University, lauded the research but cautioned against drawing overly broad conclusions.

Jackson said the study provides some of the first testable evidence of how genes influence social networks. Proving heritability of network characteristics is important, Jackson and others say, because the study of how networks form and function is rapidly expanding across disciplines, from biology to economics.

Such knowledge, Jackson said, has real-world implications and applications.

“Social networks are an important conduit of job information,” he said. “They serve as conduits for information about products. They can influence our political opinions as well as a whole variety of decisions we make, large and small.”

Fowler said it is well established that certain genes are associated with certain behaviors or health outcomes, such as smoking and obesity.

“We also know our social environment has tremendous impact,” he said. “What will be interesting to see is how social networks act as a conduit to explain why genes are associated with these health outcomes.”

A better understanding, the researchers said, could help health agencies craft more effective anti-obesity or anti-smoking programs. Last year, an international team of physicists went further, suggesting the knowledge of how networks intersect might lead to more efficient vaccination programs.

Instead of inoculating everyone during an epidemic, they said, health authorities could concentrate on vaccinating the most highly connected people to prevent them from infecting their friends, colleagues and neighbors.

One problem concerns people who are told they don’t need to get a shot. They may feel left out and, consequently, far less congenial – no matter what their genes say.

Scott LaFee
http://www3.signonsandiego.com