Languages may be grouped in many ways, but the major language groupings or families of South America may be conveniently divided into the Macro-South American Indian languages).
In the 1500s, the central Andes, the area of greatest population density in South America (about 10 persons per square mile), was sparsely populated compared to centres of Old World civilization.
Hunting and gathering peoples of the Chilean archipelago, Patagonia, the Gran Chaco, and eastern Brazilian uplands had a combined population of less than 800,000 and a density range of 0.2 (Chilean archipelago) to 1.1 (western Chaco).
The population density of the central Andes was about 200 times greater than that of the hunters and gatherers, 20 times greater than that of the tropical-forest farmers, and 30 to 40 percent greater than that of the Araucanians and the chiefdoms of the northern Andes and the circum-Caribbean.
The customs and social systems of South American peoples are closely and naturally related to the environments in which they live.The next major era is set off by incipient agriculture and also is characterized by the remains of small, hamlet-type communities along the Pacific Ocean near river mouths, where the alluvial soil was able to support crops.Technology remained simple, irrigation was not practiced, and population remained small.The southern Andes was inhabited by the Araucanians, whose combined population was possibly 1,131,000, with a density range of 0.38 to seven persons per square mile.Tropical-forest peoples numbered about 2,200,000 and had a density of 0.6 per square mile.