“Some of the things we find are frankly bizarre,” said Nicholas Christakis of Harvard University in Massachusetts, who helped conduct the study.
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 said in a telephone interview.
There could be good, evolutionary reasons for this. People in the middle of a social network could be privy to useful gossip, such as the location of food or good investment choices.
But they would also be at risk of catching germs from all sides — in which case the advantage would lie in more cautious social behavior, they wrote in the Proceedings of the National Academy of Sciences.
“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,” Fowler said in a statement.