Introduction

Environments

The Incas were the last and greatest civilization to exist in South America before the arrival of European conquerors in the sixteenth century. They both drew on institutions of the existing cultures that they conquered and developed their own unique practices that allowed them to create the most extensive empire in the New World. Their rule extended from the modern border between Ecuador and Colombia to south central Chile, including large segments of Ecuador, Peru, Bolivia, northwest Argentina, and Chile (see Figure 1).

To appreciate the Inca achievement in conquering this vast area, one has to note that western South America includes many distinct environments, from coastal deserts to tropical forests. These environments can be grouped into three major types, highland, arid coast, and tropical forest. The highland is a broad term for the regions that lie above 1000 m. For much of central Peru, the heartland of the Inca empire, the Andes mountains run in north-south trending chains, with deep valleys separating the high peaks of the chains. Altitudinal variation can be extreme, with the bottoms of the valleys lying at altitudes of around 1500m while the adjacent peaks are well above 6500 m. Rainfall occurs during the southern hemisphere summer, between October and May though the number of months and quantity of rain is variable from north to south. During the austral winter, skies are sunny, but night temperatures may drop below zero, especially in the higher altitudes. Because of the proximity of the area to the equator, day temperatures can still reach relatively high levels, making the daily temperature variation in the winter quite high.

One distinctive part of the highland zone is the region known as the Altiplano, a high, flat region that lies in southern Peru and northern Bolivia, centered on Lake Titicaca. This entire region lies near or above 4000 m, so is above the tree line, making it a vast grassland. The region is near the limits of plant agriculture, but it is ideal for the herding of ‘cam-elids’, llamas and alpacas. The arid coast extends along the western margin of South America from the Peru-Ecuador border to south central Chile, and from sea level to roughly an altitude of 1000 m. This zone is wide in far northern Peru, narrows considerably through central Peru, and then broadens out again in southern Peru and northern Chile. The Atacama Desert in the latter region is the world’s driest, with less than 10 mm of precipitation falling yearly. Cutting across this arid region is a series of rivers that have their sources in the western cordillera of the Andes. In central Peru, these rivers are approximately 25-30 km apart, but the intervalley distance widens in both far northern Peru and in Chile. The rivers are also much more deeply incised in southern Peru and Chile, restricting agriculture to a narrow strip on either side of the rivers.

Rainfall does not typically fall in the arid coastal zone. During the winter, fogs come in over the coast from the ocean, blanketing the region below 800 m. During the summer, the warmer coast causes the cool onshore moisture to rise against the western slopes of the Andes. Because rain originates in eastern South America, the Andes catch most of the rain before it can reach the western coast, which also contributes to the latter’s aridity.

The third environmental zone is the tropical rainforest. This region extends along the eastern flanks of the Andes from Ecuador to Bolivia. The rainforest proper lies below 300 m in altitude, but the zone that extends upward from that altitude to around 1500 m is called ‘montafia’, a thickly forested region. High year-round temperatures and summer rainfall make this region one with very high biological diversity.

People

The societies that occupied these three environments were as varied as the environments. There were simple fishing communities in the Lake Titicaca area of southern Peru, and powerful state-level societies such as the Chimu of the north coast of Peru. These represent the extremes, and in most areas, both the early Spanish documents and archaeological work done indicate that societies were organized into groups of villages under the control of a powerful chief or chiefs. Some of these could be quite large, such as the Colla and Lupaca of the Altiplano, while most were considerably smaller.

Coastal communities of northern and central Peru appear to have been at the higher end of the complexity scale during the period just prior to Inca expansion. As noted above, the Chimu was an empire that stretched from northern Peru to the central coast, near modern Lima. On the central coast, the Chincha society developed a hierarchical organization that was based on highly specialized occupations. In contrast, the societies of southern Peru and Chile were small and lacked significant political integration.

Chronology

The period of Inca expansion occurred just prior to the appearance of Spanish explorers along the western coast. The generally stated dates for the empire are from CE 1428-1532. These dates are from the Inca king list that was recorded by Spanish officials after their conquest of the Incas. They represent a best guess at the beginning of Inca expansion, as the Incas did not keep track of a person’s age. Archaeological work in recent decades suggests the conquests began earlier than this, but perhaps decades, not centuries, earlier. All evidence points to a relatively rapid expansion.

In the most commonly used central Andean chronological scheme, the period of Inca expansion is called the Late Horizon. A horizon is a period when a large area displays evidence of a common influence, be it a religion or conquest. The Late Horizon succeeds the Late Intermediate Period, the time when there was regional development of local polities but little large-scale integration. This period dates between CE 1000-1428.