>it was common knowledge among middle age that Earth was flat. doesn't seem an argument to me

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.

actually i meant "geocentrism" but it was too late to edit but you are right, middle age didn't thought 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

No, not defending that, since evidence points to it having been a forest, but that a place like the Amazon could form from grassland in the span of a few thousand years is absolutely possible.

the western part once turned into a huge wetland, after the Andes emerged from the ocean. that was more than 10 Ma ago although. that was also what made the western Amazonia part differ on its biodivesity

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...

There were elephants there that humans hunted to extinction, elephants typically keep forests down and create grasslands. So it seems likely it happened, and that humans was the cause (by killing the elephants).

Edit: So it is likely that the change happened and had nothing to do with the soil change.

Depends, there’s elephants in the Congo forest, they’re just not too easy to see.

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.

I never said Amazonian grasslands was manmade. Reread your own comment to understand the context

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.