During the ? rst few years of life, children acquire knowledge about the relati- ships between their own mental states, their actions, and the social world. This information is then used to understand themselves and others. Humans are born into families, where they are raised and learn to cooperate, compete, and c- municate. We are social creatures, and over the course of development, we learn about people, relationships, social systems, and others’ minds. In addition, not only do we live socially, we think socially as well. However, human adults are not the only creatures to live and think socially. In recent years, sophisticated expe- ments have provided new information about social cognition in human infants and nonhuman animals. In this book, we focus on the developmental and evolutionary origins of the social mind, bringing together the currently segregated views on social cognition in the two ? elds. Ever since the term “theory of mind” was coined by D. Premack nearly 30 years ago, the concept has been the main topic of social cognition research both in developmental psychology and in primatology. However, few attempts have been made to integrate these two research domains. Just recently, researchers from the two areas collaborated to publish a book on this topic, but the volume was little more than a collection of independent papers. This book overcomes that limitation by presenting new data and their implications from both developmental and evolutionary points of view.