Culture is information that people acquire from others by teaching, imitation, and other forms of social learning. On a scale unknown in any other species, people acquire skills, beliefs, and values from the people around them, and these strongly affect behavior. People living in human populations are heirs to a pool of socially transmitted information that affects how they make a living, how they communicate, and what they think is right and wrong. The information thus stored and transmitted varies from individual to individual and is a property of the population only in a statistical sense. Culture change should be modeled as a Darwinian evolutionary process. Culture changes as some ideas and values or ??cultural variants,?? become more common and others diminish. A theory of culture must account for the processes in the everyday lives of individuals that cause such changes. Some of these processes arise from human psychology because some ideas are more readily learned or remembered. Other processes are social and ecological. Some ideas make people richer, live longer, or migrate more often, and the resulting selective processes generate culture change. While making frequent use of ideas and mathematical tools from population biology in modeling such culture change, ultimately the theory must derive from the empirical facts of how culture is stored and transmitted.