Daniel Z. Lieberman

Carbon, hydrogen, oxygen, plus a single nitrogen atom—it is simple in form and complex in result. This is dopamine, and it narrates no less than the story of human behavior.

Each one of us has a unique way of moving. We’re usually unaware of these habits, but other people see them. Often we recognize our friends from a distance based on how they move, even when we can’t see their faces. The way we move is part of what defines us.

A Harvard study that’s been going on for seventy-four years has found that social isolation (even in the absence of feelings of loneliness) is associated with a 50 to 90 percent higher risk of early death. That’s about the same as smoking, and higher than obesity or lack of exercise.