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.

Most people who do a lot of exercise, particularly in the form of competitive athletics, have unneurotic, extraverted, optimistic personalities to begin with. (Marathon runners are exceptions to this.)

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.

Give lab rats oxytocin and, according to that meme, they get better at talking about their feelings and sing like Joan Baez.

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.

What does the frontal cortex do? Gratification postponement, executive function, long-term planning, and impulse control. Basically, it makes you do the harder thing.

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.