Why be good?

[Angrboda]

So why are we good? The simplest answer, I think, is evolution. Those who have been good at cooperating and at caring for society as well as themselves have fared better, so it has been promoted by natural selection.

This.

We evolved to be a social species and certain behaviors/values promote our success as a social species. So part of our evolving social behaviors involved developing a meta-cognitive faculty we call moral judgement. We intuitively value good behavior, and are repulsed by impulses to engage in bad behavior. It's a subconsciously driven system of influencing what our consciousness wants so as to promote behavior that benefits a social animal. In short, evolution built us to desire the good. (This basic desire is also shaped and reinforced by childhood training, along with an inbuilt desire to belong.)