We discovered that if your friend's friend's friend gained weight, you gained weight. We discovered that if your friend's friend's friend stopped smoking, you stopped smoking. And we discovered that if your friend's friend's friend became happy, you became happy.

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 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.

Everyday interactions we have with other people are definitely contagious, in terms of happiness.

People have just assumed that... if we call our Facebook acquaintances our friends, we must be influenced by them, too. But we're not.

It's fashionable to speak about vulnerable populations in medicine and public policy, but it's harder to find a more vulnerable population than those who are dying.

The reason we form networks is because the benefits of a connected life outweigh the costs. It's to our advantage as individuals and a species to assemble ourselves in this fashion.