Genetic Influences on Social Networks
46% of the variation in how many friends you have is explain by your genes. [...] 47% of the variation in whether your friends know each other is attributable to your genes. Whether your friends know each other has not just to do with their genes but with yours. [...] 30% of the variation in whether or not people are in the middle or on the edge of the network can also attributed to their genes. So whether you find yourself in the middle or on the edge is also partially heritable.
Quoted on Sun Nov 11th, 2012