ABSTRACT
The environmental limitations on the food supply held both population concentration and sedentariness to minimal levels in such regions, creating a social context that prevented adoption of advanced traits even if they became known. The environmental limitations on increased population concentration are sufficiently severe, however, to make it doubtful that greater accessibility would have permitted a significantly higher level of cultural development. The post-Tiahuanaco period, after about a.d. 1000, is characterized initially by regionalization and adaptation to local environmental situations. In the New World, three primary types of areas fall within this category: the Pacific Coasts; the Marginal Areas; and the Arctic. Along the Pacific coasts of the United States, Canada, and Chile, narrow strips of land are squeezed between the mountains and the sea. The only type of environment without a South American counterpart is the Arctic, the last refuge of the vast ice sheets that once covered much of North America.
