"Recent archaeological, ethnohistorical and ecological evidence has begun to challenge the view that 'civilizations' failed to develop in the Amazon basin due to limitations of the tropical forest environment. As a result, estimates of the native population in 1492 have become an issue of debate. These estimates are evaluated in the light of the ethnohistorical research on the Ecuadorian headwaters. Estimates are considered by examining estimated habitat densities, the impact of Old World diseases and contemporary evidence for native cultures. The study is based on documents found in archives in Quito, Seville, Madrid and Rome. It is suggested that the population of the Amazon basin in 1492 probably exceeded 5 million but that expectations of substantially higher populations appear unfounded."