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.

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.

...I might continue to believe that there is no god even if it were proved that there is. A religious friend of mine once remarked that the concept of god is useful, because you can berate god during the bad times. But it is clear to me that I don't need to believe there is a god in order to berate him.

To out-group-members, oxytocin makes you crappier - less cooperative and more preemptively aggressive. It's not the luv hormone. It's the in-group parochialism/xenophobia hormone.

The less it is possible that something can be, the more it must be.

For example, most mammals are either monogamous or polygamous. But as every poet or divorce attorney will tell you, humans are confused - After all, we have monogamy, polygamy, polyandry, celibacy, and so on. In terms of the most unique thing we do socially, my vote goes to something we invented alongside cities - we have lots of anonymous interactions and interactions with strangers. That has shaped us enormously.