Humans rely on cooperation among large numbers of unrelated group members to a much greater extent than any other animals do. Moreover, most people have social preferences that motivate them to feel concern for the welfare of others and take advantage of opportunities to behave altruistically toward others. This raises two important questions: Are differences in the form, extent, and scope of cooperation among humans and other primates associated with differences in the nature of their social preferences? How do social preferences unfold over the course of development in humans? Here, we review a growing body of research that addresses these two questions. We focus on a set of experiments that were inspired by research in behavioral economics. In these experiments, subjects are presented with choices that have different material payoffs for themselves and others, and the choices that subjects make reveal their underlying preferences. This work is allowing researchers to begin to map out the phylogeny and ontogeny of social preferences in humans and other primates.