I can't remember the article where this was stated, but we have instincts for morality because following them made our ancestors more successful. They're their for our benefit, not each others'. It seemed to your ancestors that killing someone and taking their stuff would be a net benefit, and if they didn't have a built-in aversion they'd do it, and they would likely get caught and punished.
I can't remember the article where this was stated, but we have instincts for morality because following them made our ancestors more successful.
I believe you're thinking of the ethical injunction sequence. Specifically, the post ethical inhibitions.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.