Human beings, Haidt argues, are “the giraffes of altruism.” Just as giraffes got long necks to help them survive, humans developed moral minds that help them and their groups succeed. Humans build moral communities out of shared norms, habits, emotions and gods, and then will fight and even sometimes die to defend their communities.

Different interpretations of evolution produce different ways of analyzing the world. The selfish-competitor model fostered the utility-maximizing model that is so prevalent in the social sciences, particularly economics. The new, more cooperative view will complicate all that.

But the big upshot is this: For decades, people tried to devise a rigorous “scientific” system to analyze behavior that would be divorced from morality. But if cooperation permeates our nature, then so does morality, and there is no escaping ethics, emotion and religion in our quest to understand who we are and how we got this way.