Prehistoric society

What was prehistoric society like in the area surrounding the Amazon River Basin? How do scholars learn about prehistoric cultures? What factors led to the ability of the European nations to dominate the New World civilizations?

Details: Discuss the following questions:

How are scholars able to find out how early people with no written records lived?
What was prehistoric society like around the Amazon?
What ensured European domination in the New World?
How do you think an entire prehistoric group of people could simply disappear, such as the people around the Marajo of the Amazon?

Please list any references or web sources.