It's only bizarre if you say it like that. Genes determine personality (at least to some extent), personality determines whether you have friends that would like one another. Some people have much more heterogeneous tastes in people than others. Yes, this poses certain problems for naive applications of network theory to human interactions, but that's only radical if you're a naive network theorist.
"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.
One surprising finding is that an individual's genetic makeup can influence the behavior of others, Fowler said: "My genes can influence the probability that two of my friends will become friends of each other."