January 27, 2009
Genetically Inherited Places In Social Networks

One's place in social networks is at least partially genetically inherited.

CAMBRIDGE, Mass. and SAN DIEGO, Calif. Can't help being the life of the party? Maybe you were just born that way. Researchers from Harvard University and the University of California, San Diego have found that our place in a social network is influenced in part by our genes, according to new findings published in the Proceedings of the National Academy of Sciences.

This is the first study to examine the inherited characteristics of social networks and to establish a genetic role in the formation and configuration of these networks.

The research was conducted by Nicholas Christakis of Harvard, who is professor of sociology in the Faculty of Arts and Sciences and professor of medical sociology at Harvard Medical School, Christopher Dawes and James Fowler, both of UC San Diego.

"We were able to show that our particular location in vast social networks has a genetic basis," says Christakis. "In fact, the beautiful and complicated pattern of human connection depends on our genes to a significant measure."

Feel doomed to a life on the periphery? It could be your genetic fate. Does that make you any more reconciled to your lot in life?

My reaction to the next paragraph: of course if genes affect personality they'll affect structures of social networks. Think gregarious people are going to play the same roles as the painfully shy? Of course not.

While it might be expected that genes affect personality, these findings go further, and illustrate a genetic influence on the structure and formation of an individual's social group.

The researchers found that popularity, or the number of times an individual was named as a friend, and the likelihood that those friends know one another, were both strongly heritable. Additionally, location within the network, or the tendency to be at the center or on the edges of the group, was also genetically linked. However, the researchers were surprised to learn that the number of people named as a friend by an individual did not appear to be inherited.

The study included national data (from the National Longitudinal Study of Adolescent Health) for the social networks of 1,110 adolescent twins, both fraternal and identical. The researchers compared the social networks of the identical twins to those of the fraternal twins, and found greater similarity between the identical twins' social network structure than the fraternal twins' networks.

I like this idea: Behaviors that make people more alone and on the edge reduced their risk of dying from bubonic plague and other diseases. The selective pressures to boost human immune response have been very strong in the last few thousand years in urbanizing populations and in grain farming populations as these changes in lifestyle brought more people into close contact.

There may be an evolutionary explanation for this genetic influence and the tendency for some people to be at the center while others are at the edges of the group, according to the researchers. If a deadly germ is spreading through a community, individuals at the edges are least likely to be exposed. However, to gain access to important information about a food source, being in the center of the group has a distinct benefit.

"One of the things that the study tells us is that social networks are likely to be a fundamental part of our genetic heritage," says Fowler, associate professor of political science at UC San Diego. "It may be that natural selection is acting on not just things like whether or not we can resist the common cold, but also who it is that we are going to come into contact with."

Of course social networks are a product of our genetic heritage. Look at other animal species. The amount that they socialize and the nature of their social structures (more or less hierarchical, with males or females in charge, and other characteristics) vary by species. Humans are just another species that happens to be smarter. We still have a large number of social behaviors with obvious genetic causes such as sexual attraction and tendencies to form hierarchies.

This all reminds me of a new book by Gregory Cochran and Henry Harpending, The 10,000 Year Explosion: How Civilization Accelerated Human Evolution. I'll be writing a review of it Real Soon Now. In the mean time, start reading the first installment of Michael Blowhard's interview of Greg about the book.

Share |      Randall Parker, 2009 January 27 12:09 AM  Brain Society

Annalise said at January 27, 2009 7:15 AM:

Interesting research!


Jason Malloy said at January 27, 2009 7:14 PM:

One of the strongest predictors of sexual partner number (besides years married), is extroversion. So sexually transmitted disease is probably also a contingent cap on that trait.

Previous research shows that position in social hierarchy is rapidly re-created when people are shuffled together into completely new groups:

"In several remarkable studies, researchers have brought together
students from different schools, representing different levels of the
social hierarchy. Within hours, sometimes less, the children assume
their accustomed places
the popular ones on top, the socially
awkward on the bottom. Climbing out of the geek ghetto is hard, even
if a child knows what likeability looks like."


Walter Albertson said at January 28, 2009 10:15 AM:

The bird a nest, the spider a web, man friendship.
- William Blake

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