Scientists find evidence discrediting theory Amazon was virtually unlivable

...scientists now believe that instead of stone-age tribes, like the groups that occasionally emerge from the forest today, the Indians who inhabited the Amazon centuries ago numbered as many as 20 million, far more people than live here today.

"There is a gigantic footprint in the forest," said Augusto Oyuela-Caycedo, 49, a Colombian-born professor at the University of Florida who is working this swath in northeast Peru.