The belief that the pre-columbian indians were small in numbers and lived in sparsely populated and isolated tribes is a myth. They were very numerous, had complex economies, and lived in very large cities throughout the Americas. When the first wave of Europeans came to America, half of the worlds population lived in the Americas. Much evidence suggests that deseases that were brought in by the first wave killed over 90% of the Indian population before the second wave ever arrived. By that time, over 40 years later, Forests that largely didn't exist 40 years before had taken over farm lands and entire cities. The only peoples that survived were the small isolated tribes. Thus the myth that we have.
So the authors history is completely backwards.