If we look at things on a relatively abstract level, perhaps even a scenario where the America’s are colonized by humans thousands of years sooner while Old World Civilizations run into as many problems starting as possible, how far can pre-industrial humans push agriculture and major population centers into the Amazon?
Can we get human civilization with high population density throughout the Amazon, if we give them thousands of extra years before Afro-Eurasian contact, great enough trade, a number of ATL domestications, the luck of a few ships that don’t have Old World Disease but do have valuable old world animals, etc...
What kind of population might be able to fit into a truly wanked enough Amazonian population? What (if any) impact might this have on human civilization?