Much research has been conducted to document and sometimes to provide proximate explanations (e.g., Confucianism vs. Western philosophy) for East–West cultural differences. The ultimate evolutionary mechanisms underlying these cross-cultural differences have not been addressed. We propose in this review that East–West cultural differences (e.g., independent versus interdependent self construal; autonomy versus harmony in values; hierarchical versus egalitarian relationships) result from social learning and individual learning as primary means to adapt to the local environment. Historical and contemporary evidence from multiple sources is reviewed that indicates smaller extents of environmental variability in East Asia including China than in Europe and North America, favoring social learning in the East and individual learning in the West. Corresponding to these different adaptive strategies, East–West differences stem from learning styles that differ between copying and rote memorization, on the one hand, and critical thinking and innovative problem solving, on the other hand. These primary cultural differences are correlated with such personality attributes as conformity, compliance, and independence that serve to facilitate social or individual learning. This and other cross-cultural and educational psychological research is reviewed as evidence to support our evolutionary explanation of why Eastern and Western cultures differ in the ways in which they do.