As in Mesoamerica, in the Andes social organization and religion shaped ideas of spiritual kinship as well as patterns of production and trade. The ayllu (EYE-you), or clan, served as the fundamental social unit of Andean society. Kinship was based on a shared ancestor, or huaca, who could be a once-living person whose remains were mummified and preserved, but could also be an animal spirit or a combination of the two. Members of an ayllu considered their huaca as more than a spirit: it was an entity that owned lands the ally’s farmers tended, and the huaca served as the center of community obligations such as the pooling of labor.

Ancestor worship provided the foundations of Andean religion and spirituality, served as the basis of authority, and guided food production. All members of the ayllu owed allegiance to kuracas, or clan leaders, who typically traced the most direct lineage to the ancestor, or huaca. This lineage made them both temporal and spiritual leaders of their ayllu. An Andean family’s identity came from membership in an ayllu’s ancestral kinship, and its subsistence came from participation in the broader community’s shared farming across vertical climate zones. People often labored collectively and reciprocally.

Andean history unfolded in a cycle of centralization and decentralization. There were three great periods of centralization, which archaeologists call the Early, Middle, and Late Horizon. The Late Horizon, which included the Inca Empire, was the briefest, cut short by the Spanish conquest (see “The Fall of the Incas”). The first period, the Early Horizon (ca. 1200–200 B.C.E.), centered on the people of Chavín, upland from present-day Lima. The Chavín spread their religion along with technologies for the weaving and dyeing of wool and cotton. Weaving became the most widespread means of recording and representing information in the Andes.

After the end of the Early Horizon, regional states emerged, including Moche (MOH-cheh) civilization, which flourished along a 250-mile stretch of Peru’s northern coast between 100 and 800 C.E. The Moche people developed complex irrigation systems, with which they raised food crops and cotton. Each Moche valley contained a large ceremonial center with palaces and pyramids surrounded by settlements of up to ten thousand people. Moche artifacts reveal a remarkable skill in metalwork and pottery.

Politically, the Moche were organized into a series of small city-states rather than one unified state, and warfare was common among them. Beginning about 500 the Moche suffered several severe El Niños, changes in ocean current patterns in the Pacific that bring searing drought and flooding. They were not able to respond effectively to the devastation, and their urban population declined.

Pan-Andean cultures re-emerged during the Middle Horizon (500–1000 C.E.), centered to the south in Tiwanaku, near Lake Titicaca, and to the north at Wari, near present-day southern Peru. The city-state of Wari’s dominion stretched from the altiplano north of Lake Titicaca to the Pacific coast, drawing on Moche cultural influences. Its reach between mountain and coastal regions led to extensive exchanges of goods and beliefs between ecologically different farming zones. The city-state of Tiwanaku extended its influence in the other direction, south of the lake.

Storms and climate shifts were central to Andean people’s worldview because changes in climate, particularly abrupt changes brought by El Niño, could devastate whole civilizations. El Niño disrupted Moche culture and contributed to the decline of Wari and Tiwanaku. As the Middle Horizon ended, the cities of Tiwanaku and Wari endured on a smaller scale, but between 1000 and 1200 C.E. they lost their regional influence. The eras between the Early, Middle, and Late Horizon, known as Intermediate Periods, were times of decentralization in which local cultures and practices re-emerged. It was out of these local developments that new centralizing empires would over time emerge.