If your friends are obese, your risk of obesity is 45 percent higher. ... If your friend's friends are obese, your risk of obesity is 25 percent higher. ... If your friend's friend's friend, someone you probably don't even know, is obese, your risk of obesity is 10 percent higher. It's only when you get to your friend's friend's friend's friends that there's no longer a relationship between that person's body size and your own body size.

What constrains or enables the capacity of human beings to work in groups is not so much the technology, but rather the capacity of the human brain to have and monitor social interactions.

I like to have met someone in real life before being their Facebook friend.

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.

It is well to look around at whom, and not just what, surrounds us. Population structure will change everything. Our health, wealth, and peace depend on it.

The social sciences offer equal promise for improving human welfare; our lives can be greatly improved through a deeper understanding of individual and collective behavior. But to realize this promise, the social sciences, like the natural sciences, need to match their institutional structures to today's intellectual challenges.

We are, first of all, not solitary creatures and second of all, we are deeply embedded in the lives of others. It's very easy to forget that and to engage in an atomistic fallacy - where we think that all we have to do is study the individual components of a system in order to understand the system. That's clearly not the case when it comes to social systems.