The developing view is that the population of the Americas was many millions more than the "empty" land found by the Europeans after the Spaniards. These populations were decimated by European diseases. (The Amerindians got a little tit for tat by giving syphilis back to the Europeans.) Satellite archaeology has shown that the Amazonian jungles contain vast abandoned cities. The natives fled into the jungle, weakened by disease, and broke off contact with the outside world. Back in the early '80s, NatGeo magazine had a picture of Amazonian Indians carrying a litter, with some sort of dignitary on it. Their bodies had been painted to resemble Spanish conquistadors, armor and all. They had even plucked out their hair into a tonsure. (They don't go bald.) I was dating a Puerto Rican girl at the time. When I pointed it out, she said "Who told you that?" (That was not a long-lasting relationship.
) Later, when I read in the book "1493," about the abandoned cities, the picture from the magazine jumped into my mind. Eureka!