For any society, change is inevitable. Cultures change at different rates and times. Two basic processes bring about culture change. The first process is the interaction of discovery and invention—the addition of new knowledge about the world and the application of that knowledge through the creation of concrete or abstract artifacts. Innovations are selected and modified to fit a society's existing cultural system. Possibilities for innovation within any given society, however, are limited.

The second process of culture change—diffusion—is responsible for the majority of any society's cultural inventory and explains the diversity in level of societal complexity. Diffusion is the process of cultural borrowing. Isolated societies, with limited exposure to the innovations of other groups, change slowly. Societies that live in areas with greater intercultural contact change more rapidly. As with innovations, potentially borrowed items are selected for their fit within the receiving society's system. When borrowed, they are modified to fit the system.

Acculturation is rapid diffusion under the influence of a dominant culture. This may take place by force, as in military conquest, or voluntarily, as with the cargo cults of the South Pacific.

Revolution is rapid invention—change from within a society that alters the whole social fabric. Revolutions may involve violent overthrows of existing governments or more peaceful cultural statements, such as religious revolutions or the changes seen in United States society that began in the 1960s.

Early theories of cultural evolution were often oversimplified models stressing one process of change—either independent invention or diffusion. Thanks in part to the Boasian school of thought, we now see that all the processes of change work together in complex ways that vary with each society's particular history.