The central Peruvian desert coast extends southward through several valley systems. The major rivers that descend to the Pacific and break the desert are the Pativilca, Huaura, Chancay, Rimac and Chillon, Malay, Caiiete, Chincha, Pisco, lea, and Nazca. At the time of the conquest, most residents of the central coast subsisted on the basis of irrigation agriculture, with food supplemented by marine resources. Most of the area was brought into the Inca Empire through conquests between 1460 and 1480. Pachacamac was the most important center in that sector of the Peruvian coastal region. It contained a relatively dense urban population and, as the chief ceremonial shrine along the entire coast, attracted a large number of temporary residents.

The central Peruvian highland corregimientos are in the heart of the Andean chain. The elevation of the area is high. The frigid, windswept pun a appears inhospitable but provides fodder for extensive flocks of llamas and alpacas, which are used for wool. Upper sections can also produce ichu and quinoa, a native cereal. Potatoes and other tuberous crops are grown in cool zones, and in the more temperate valleys wheat, corn, and other crops are cultivated. The central highlands are a major mining region of the Peruvian Andes. The modern Cerro de Pasco mining district is in the north; minor silver deposits were worked throughout the central highlands; famous mercury mines are located at Huancavelica in Chocorvos; and there was a major silver-mining center at Castrovirreyna in the southern part of the same corregimiento. In this chapter we shall examine the relationship between mining, which was so important in the central sierra, and population change.

In the preceding pages we attempted to gauge the magnitude of Peru's preconquest population. By any standards the Inca population was large. Perhaps 9 million people resided within the limits delineated by Peru's contemporary boundaries. The number of inhabitants remaining a century after contact was roughly a tenth of those that were there when the Europeans invaded the Andean world. In the following chapters we shall examine the transformations that were taking place as a result of the demographic collapse of native America. The impact of population change varied from one place to another within Peru. Some Indian communities were wiped out. In a few cases numbers actually increased, in spite of the general downward tendency. We shall examine these developments in as great detail as possible. Analysis is within the framework of major geographical regions. We have already seen the differences between coastal and highland change. More subtle variations are discernible as one moves southward, down the Peruvian coast. Although on occasion such a structure becomes too rigid, the results are useful for comparative analysis.