Brains distinguish between an Us and a Them in a fraction of a second. Subliminal processing of a Them activates the amygdala and insular cortex, brain regions that are all about fear, anxiety, aggression, and disgust.

How much you groom somebody else is more important than who grooms you.

The gigantic challenge is the magnitude of the individual differences in the optimal set point for "good stress." For one person, it's doing something risky with your bishop in a chess game; for someone else, it's becoming a mercenary in Yemen.

But if you get chronically, psychosocially stressed, you're going to compromise your health. So, essentially, we've evolved to be smart enough to make ourselves sick.

Only humans invent moralizing gods who monitor our behavior.

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.

...when doing science (or perhaps when doing anything at all in a society as judgmental as our own), be very careful and very certain before pronouncing something to be a norm - because at that instant, you have made it supremely difficult to ever again look objectively at an exception to that supposed norm.