1491

Chapter 8 describes the rise, flourishing, and decline of a range of civilizations in Mesoamerica and North America. The first of these is the conflict between the city-states of Kaan and Mutal, in 4th-century A.D.; following the war, over the next several centuries, the Mayans abandon their cities. Mann states that among the possible hypotheses for this urban abandonment, severe drought is the most likely; this drought would have been compounded by overpopulation and land deformation. The large city-states, Mann argues, were vulnerable to local fluctuations in the climate, which in turn caused massive urban exodus.

This pattern of land deformation appears in Mann's next section, which details societies along the Hudson and Mississippi rivers. The chief tool of these progressive deformations is fire, which gradually reshapes the land. Up the Mississippi River, near the border of Illinois and Missouri, the author describes the city-state of Cahokia, the most famous of the "mound cities"—mysterious sites characterized by semi-circular constructions believed to be pyramidal at one time but which now resemble large circular mounds. For these communities, erosion and flooding proves to be a devastating combination.