We and others have done a bunch of work to show that if your real friends online say or do something, it affects you. But if your acquaintances online say or do something, it does not. People on average have about 106 Facebook friends, but only 5 or 6 real friends.

Realizing the ways in which we humans may have been inadvertently changing our genes for millennia provides a way for us to begin to think about the inevitable genetic revolution in medicine that is going to allow us to advertently change our genes over centuries and even decades.

It used to be thought that our genes were historically immutable and that it was not possible to imagine a conversation between culture and genetics.

Nicholas A. Christakis Quotes