Are humans basically selfish, or basically giving? There's a widespread assumption that you have to offer people incentives to do good deeds, or threaten punishment to stop them from doing evil deeds. But the way people act in the real world contradicts that idea. Humans may actually have been shaped by evolution to care about each other, to share, and to cooperate. Evolutionary biologists, anthropologists, psychologists and others explore this question, "Why do we share?"