Peru may have lagged somewhat behind the Mexican and Guatemalan development, but the “classic” period of the three major cultures of Peru is thought to coincide fairly closely with the classic ages of the Mayan and Toltec temple states. Potatoes and the llama were important resources of the Andes slopes not available in Mexico. In addition, the Peruvian societies of the coastal area depended on a very skillful irrigation, whereas in Central America maize was grown on rain-watered land. At some date between A.D. 500 and 1000 all of the Peruvian valleys that plunge down to the Pacific were overrun by an art style originating in the high Andes at Tiahuanaco. Perhaps this attests military conquest, though it may represent some religious movement. Whatever its nature, centralization did not survive for long. When the Incas began to develop a new empire from a center in the high Andes, their expanding power met and overcame a series of local city and tribal states (fifteenth century). The Incas imposed a very strictly centralized regime upon all of Peru. Their empire was linked together by roads, officials, and a religion of the sun, of which the Great Inca was chief priest. The resemblance to the religio-political centralization of ancient Egypt is striking.
The Mexican area was more various and may be compared in this respect to ancient Mesopotamia. About A.D. 900 Mayan and Toltec priest-led communities broke down. The reasons are not clear. In the central valley of Mexico it seems probable that barbarian invasion from the north brought down the Toltec regime. Further south, traces of military assault are lacking, and it is possible that some withdrawal of belief, whereby the Mayan farmers ceased to find it necessary to support the priestly centers in order to assure the fertility of their maize fields, accounts for the abandonment of the temple sited. Nevertheless, more militaristic regimes did come to the Mayan lands. First Chichen Itza in Yucatan and then Mayapan seem to have created a sort of loose empire among the Mayans, but by the time the Spaniards arrived, even this sort of political unity had vanished. Despite their past, attested by the great temple centers Mayan agriculturalists were living in simple village communities when the Spaniards first appeared and had no elaborate military, political, or even priestly organization.