In the fourth chapter, "Pyramid Schemes", the fates of the Roman and Mayan civilisations are compared; both peaked with centralised empires but ended with power being diffused to their periphery as the center collapsed and ultra-conservative leadership refused reformations. Anthropologist Joseph Tainter's explanation for the fall of the Roman Empire is invoked, that "complex systems inevitably succumb to diminishing returns" so that the costs of operating an empire are so high that alternatives are implemented. Two examples of civilisations that have been sustainable are described: China and Egypt. Both had an abundance of resources, particularly topsoil, and used farming methods that worked with, rather than against, natural cycles, and settlement patterns that did not exceed, or permanently damage, the carrying capacity of the local environment.
