" Darwin, on grounds such as this, believed that the human species is a moral one—that, in fact, we are the only moral animal. “A moral being is one who is capable of comparing his past and future actions or motives, and of approving or disapproving of them,” he wrote. “We have no reason to suppose that any of the lower animals have this capacity. "

― Robert Wright , The Moral Animal: Why We Are the Way We Are - The New Science of Evolutionary Psychology