[svensken]

Humans have arbitrary morals in much the same way that wolves have arbitrary instincts to pack-hunt; many preceding generations have survived thanks to that particular characteristic, so the modern individuals abide by the behavior, not even fully aware that it happens to increase their chances of survival. The mechanism works the same both for adopted social behavior and for evolved instinct.

But I'd like to make the argument that the central moral imperatives put forth by the bible (as well as by many other religions) would exist as moral imperatives even without religion itself; natural selection would popularize them no matter what.