In a sense, the theory of cultural evolution is powerful and compelling because the assumptions are minimal and the conclusions sweeping. If people learn from each other, and if these processes are not random, cultural evolution must occur. In another sense, however, the theory is underdeveloped because social learning can be something other than random in a truly staggering number of ways, and the details are critically important for how cultures evolve.
The link between social learning at the individual level and cultural evolution at the aggregate level is a basic question in the evolutionary study of human behavior. It is also a fundamental policy issue. Policy makers and development agencies are widely engaged in applied cultural evolution in that they are trying to steer cultural evolution in ways that are consistent with policy objectives. The challenge, of course, is that we do not know most of what we need to know about cultural evolution to do this effectively.