> There wasn't a single civilization there.

That's what I said. There have been multiple. The linked article is about the Aquiry civilization which numbered 3 million people in only 3% of the land. The Marajoara outlasted them. The Upano Valley civilization predates both of them by 100 years and built dense garden cities. The Beni Mounds spanned over 20k earthen mounds and human-made forest islands that were connected by massive canals and causeways