The Inca and Aztec Empires that encountered Spanish conquerors were short-lived products of the cycle of centralization and decentralization that had characterized the Andes and Mesoamerica for thousands of years. The empires preceding those of the Incas and Aztecs had been undone when their own people turned against them, when climate changes disrupted them, or when they faced outside competition. What was new in the sixteenth century was that this outside competition came from Europeans.

The civilizations of the Andes and Mesoamerica from which the Incas and Aztecs emerged had remarkable similarities with and differences from other ancient and premodern civilizations in other regions of the world. Indigenous societies of the Americas developed extensive networks of trade. In Mesoamerica and the Andes, the domestication of crops led to the kind of bountiful production that allowed for diversification of labor among farmers, priests, nobles, merchants, and artisans. In these environments, cycles of centralization occurred in which powerful city-states emerged and embarked on campaigns of conquest, bringing vast regions under their political, religious, and cultural influence.

But civilizations of the Americas developed in unique ways as well. This was particularly true in the Andes, where peoples developed specialized patterns of farming in vertical archipelagos in their inhospitable mountain environment. Similarly, though Andean peoples did not develop writing, they instead developed the khipu into a sophisticated system of recording and communicating information.

Ultimately, the history of the peoples of the Americas was defined by their diverse experiences as they coped with varied climates, ecology, and geography. And peoples’ experiences of adapting to their environments, and of transforming those environments to meet their needs, shaped the ways they understood their world. These experiences led them to produce precise calendars, highly detailed readings of the stars, and an elaborate architecture of religious beliefs through which they interpreted their relationships to their world and their place in the cosmos.