The problem isn't testosterone and aggression; it's how often we reward aggression. And we do: We give medals to masters of the "right" kinds of aggression. We preferentially mate with them. We select them as our leaders.

Pulling a gun's trigger can be an appalling act. But if it is suicidal drawing fire to save someone, it has an utterly different meaning. Placing your hand on someone's arm can be an act of deep compassion or the first step of betrayal. The punch line? It's all about context, and the biology of context is vastly more complicated than the biology of the behavior itself.

Depression is not generalized pessimism, but pessimism specific to the effects of one's own skilled action.

The fascinating thing about our best and worst behaviors isn't the behavior itself - the brain tells the muscles to do something or other - big deal. It's the meaning of the behavior.

Oxytocin is lauded for how it promotes warmth, generosity, social bonding, cooperation, trust, and compassion.

Get it wrong, and we call it a cult. Get it right, in the right time and the right place, and maybe, for the next few millennia, people won't have to go to work on your birthday.

If you live in a baboon troop in the Serengeti, you only have to work three hours a day for your calories, and predators don't mess with you much. What that means is you've got nine hours of free time every day to devote to generating psychological stress toward other animals in your troop. So the baboon is a wonderful model for living well enough and long enough to pay the price for all the social-stressor nonsense that they create for each other. They're just like us: They're not getting done in by predators and famines, they're getting done in by each other.