Humans are the last of their tribe. Our closest cousins such as Australopithecus and Neanderthals are extinct. Of the remaining members of our closest family, we have only the other great apes, chimpanzees, bonobos, gorillas and orangutans. And of these, humans have uniquely expanded their population to become a dominant force in the world. Not so much time – a few million years – separates us from our closest living relatives, and most of the change has occurred very recently. One of the key factors has been our hyper-cooperative nature. We collaborate with and help nonkin in a way that is unique in the animal kingdom. But we are also uniquely anti-social and competitive. We compare our losses and gains to others, are terribly sensitive to unfairness and will punish others for transgressions. Both the better and worse sides of our nature might share a common substrate. To explore this, I will describe some experimental work on children and chimpanzees. The key insights are that concern for the welfare of others – both for better and for worse – may be uniquely human, the capacities for which emerge early in our lives.