Gerhard Lenski's ecological-evolutionary theory of human societies, originally presented and tested in Power and Privilege (1966) and Human Societies (1970), makes a number of general and specific predictions about the impact of subsistence technology on the fundamental features of societies, as well as identifying constraints that the techno-economic heritage of currently industrializing societies continue to exercise on their development trajectories. This paper reviews the strategies adopted for presenting and for testing the theory, critically analyzes and extends some important results of its empirical tests, and explores issues confronting the future development and presentation of the theory.