https://en.wikipedia.org/wiki/Metallurgy_in_pre-Columbian_Am...
On the ecological side, some anthropologists argued that humans actually played a major role in transitioning Amazonia from mostly grasslands to the rainforest it is today around 10,000 years ago.
The distribution of many plant species is inexplicable without looking at human settlement patterns. So much so that other anthropologists have called the Amazon a "manufactured landscape".
https://sci-hub.ru/https://link.springer.com/chapter/10.1007...
now, wow, calling it a grassland before humans 10,000 years ago is to smoke too much pot before reading/making papers. 5,000,000 AD then yes, maybe... /s but Terra Preta and other indigenous interferences is not even 10% of Amazon territory. various other animals are responsible for spreading diversity be it by shitting seed or just moking stuff around to make nests or impress some partner. the rainforest are also there because mountains changing courses of rivers.
[0] "Geology and geodiversity of the Amazon: Three billion years of history" https://www.theamazonwewant.org/wp-content/uploads/2022/05/C...
[1] the grassland hypothesis (somewhere in the text) and other curiosities about its biodiversity https://www.science.org/content/article/feature-how-amazon-b...
> There is evidence that there have been significant changes in the Amazon rainforest vegetation over the last 21,000 years through the last glacial maximum (LGM) and subsequent deglaciation.
https://en.wikipedia.org/wiki/Amazon_rainforest
Also, there's this:
https://www.discovermagazine.com/planet-earth/10-800-years-a...
your last link is about Llanos de Moxos, which isn't in Amazon. you don't seen to understand even basic geography... even if Llanos was 100% man-made (and isn't) and it was part of the Amazon (and not a region that borders it) it would be the equivalent of 2.6% of the whole Amazon area. concluding such a thing because 3% of an area that benefited (soil quality wise) from billions of years of geologic events and was partly modified by humans is ignorant but again, Llanos isn't even Amazon
it was common knowledge among middle age that Earth was flat. doesn't seem an argument to me
Edit: So it is likely that the change happened and had nothing to do with the soil change.
The Wikipedia source was to back up the claim that Amazonia was largely grasslands about 10-20k years ago. That is what is common knowledge.
And you don't seem to know basic history, casting doubt on other things you say. Nobody serious in the middle ages (or since much further back than that either) thought seriously that the Earth was flat.
now if you are defending this absurd commentary that Amazonia was a grassland 10,000 years ago and turned out to be what's because humans, i think you both are on the level of flat earth 21° century people
humans may altered the biodiversity of Amazonia by breeding only wanted species. but we don't have too much evidence of that (yet). but if it was, the biodiversity of pre-humans was probably richer, as indigenous apparently managed the forests with fire and farmed hyperdominant cultures [0]
[0] https://portal.amelica.org/ameli/journal/181/1813954027/html...
The trees grow faster than the elephants can wreck them. But in areas with less rain fall elephants keep the grasslands more open.
As did Mammoths in the northern forests.