"Culture is cumulative in the sense that the body of information in the cultural repository does not remain static, but can itself grow larger and more complex. Grass huts evolve into wood-frame houses, then brick buildings, and eventually skyscrapers. Tribal leaders evolve into kings, then emperors, then prime ministers. Simple sets of norms evolve into more complicated informal institutions, then byzantine formalized legal codes. As each generation adds its own new innovations, discoveries, and improvements, functional sophistication is accumulated in cultural traits in much the same way as it is accumulated in genetic traits.”