The article discusses the role of gender in within-society variation in cooperative behavior, and whether gender differences in cooperation emerge similarly across diverse societies. The authors use cross-cultural datasets of 4- to 15-year-old children's preferences for equality in experimental tasks measuring prosociality and fairness to investigate these questions. They find that gender has little impact on the development of prosociality and fairness within the datasets, and there is not much evidence for substantial societal variation in gender differences. The authors discuss the implications of these findings for understanding the nature and origin of gender differences in cooperation and for future research.