Western North America

摘要: The western United States is a mountainous land with strong climatic gradients and vegetation ranging from subtropical desert-scrub to tundra. region has dynamic past, especially over the last 20,000 years, when large lake-systems developed then desiccated few modern remnants in now-arid interior, alpine glaciers ice-caps advanced retreated. Humans appeared on scene as lakes waned, witness (or perhaps cause) extinction of camels, horses, mammoths, ground-sloths other elements magnificent Pleistocene mammal fauna. Archaeological data illustrate continual struggle human societies 10,000 years cope harsh continually changing climate. Long-term regional periods warmth aridity during this period apparently forced prehistoric migrations played major role development Southwestern pueblo (Cordell, 1984).