Our purpose here is to describe and illustrate in the simplest possible way a multiple-phase theory of economic growth and development that helps explain why human evolution has not been characterized by steady progress but by fluctuating growth and changing forms, sometimes progressing to higher levels of complexity and sometimes reverting to earlier stages of organization. In the form outlined here (in terms of macroeconomic growth theory) it is convenient to think of the analysis as involving the “very long run.” But for reasons that will be suggested in the conclusion, the very long run is of great interest for interpreting events in the “very short run,” in particular the processes of integration and disintegration currently at work in the world.