January 27, 2009

Genetics Dictate How Humans Get Along

The way humans make friends and interact with them may be closely linked to genetic variations, according to new research.

"The evidence we present here suggests that egocentric properties are significantly heritable in human social networks," said Nicholas Christakis, of Harvard University in Massachusetts, and James Fowler of the University of California San Diego.

"Although it may not be surprising that genetic variation influences net work formation, the effects are large enough that it is hard to argue that they can be ignored."

Christakis and Fowler worked with Christopher Dawes of UCSD using national data that compared more than 1,000 identical and fraternal twins. Their study is published in the Proceedings of the National Academy of Sciences.

Researchers tested their hypothesis by comparing trait similarity in (same-sex) monozygotic twins who share 100 percent of their segregating genes to trait similarity in same-sex dizygotic twins who share only 50 percent on average.

"We find that how interconnected your friends are depends on your genes. Some people have four friends who know each other and some people have four friends who don't know each other. Whether Dick and Harry know each other depends on Tom's genes," Christakis told Reuters.

"We found there appears to be a genetic tendency to introduce your friends to each other," said Christakis, a professor of medical sociology in the Department of Health Care Policy at Harvard Medical School.

There could be good, evolutionary reasons for this, researchers said.

"Social networks may serve the adaptive (or maladaptive) function of being a vehicle for the transmission of emotional states, material resources, or information (e.g., about resource or partner availability) between individuals," they concluded.

"Some traits that appear to spread in social net works also appear to be heritable (such as obesity, smoking behavior, happiness, and even political behavior, suggesting that a full understanding of these traits may require a better understanding of the genetic basis of social network topology."

"Another area of future research should be the identification of mediating mechanisms like personality traits and the specific genes that may be involved," they wrote.


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