Humans exhibit extensive large-scale cooperation, of a form unprecedented in the natural world. Here I suggest that this cooperation arises in our species alone because of our uniquely potent capacities for social learning, imitation and teaching, combined with the co-evolutionary feedbacks that these capabilities have generated on the human mind. Culture took human populations down evolutionary pathways not available to non-cultural species, either by creating conditions that promoted established cooperative mechanisms, such as indirect reciprocity and mutualism, or by generating novel cooperative mechanisms not seen in other taxa, such as cultural group selection. In the process, gene-culture co-evolution seemingly generated an evolved psychology, comprising an enhanced ability and motivation to learn, teach, communicate through language, imitate and emulate, as well as predispositions to docility, social tolerance, and the sharing of goals, intentions and attention. This evolved psychology is entirely different from that observed in any other animal, or that could have evolved through conventional selection on genes alone.