Researchers from UCSD and Harvard University have found that our place in a social network is influenced, in part, by our genes.
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.
The researchers compared the social networks of 1,110 adolescent twins, both fraternal and identical, and found greater similarity between the identical twins' social network structure than the fraternal twins' networks.
The findings also illuminate a previously unknown limitation of existing social network models, which had assumed that all members' behavior was interchangeable.
"What our paper shows is that human social networks are different from other kinds of networks," said James Fowler, Ph.D., an associate professor of political science at UCSD.
"You can take a router from one part of the Internet and swap it for another, and nothing will change," he continued. "But humans are different. We have inherent characteristics that make each of us more like snowflakes than interchangeable cogs in the machine."
A step beyond
To address these intrinsic differences in human beings that contribute to the formation of social networks, the researchers have created a new mathematical model, called the "attract and introduce" model, which supports the genetic variation of members. 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.
"Each of us carries with us a tendency to gravitate towards a certain part of the social network," Fowler said.
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 a 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.
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 findings are published in the Jan. 26, 2009, "Proceedings of the National Academy of Sciences (PNAS)."