If you care about your longevity and health, be a socially affiliated baboon who is better than high-ranking ones at walking away from provocations.

Fossey, Fossey, you cranky difficult strong-arming self-destructive misanthrope, mediocre scientist, deceiver of earnest college students, probable cause of more deaths of the gorillas than if you had never set foot in Rwanda, Fossey, you pain-in-the-ass saint, I do not believe in prayers or souls, but I will pray for your soul, I will remember you for all of my days, in gratitude for that moment by the graves when all I felt was the pure, cleansing sadness of returning home and finding nothing but ghosts.

The frontal cortex doesn't even fully develop until age 25, which is wild!

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.

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.

It's probably even the case that if you stoked up some Buddhist monks with tons of testosterone, they'd become wildly competitive as to who can do the most acts of random kindness.

Naturally, things are more complicated - those groovy, pro-social effects of oxytocin apply to how we interact with in-group members.