(Apparently, I need to apologise.)
I don't believe scientists should apologise for communicating facts, so here is more info on it...
It was home to millions of people, who shaped the landscape even today.
We know this from several pieces of evidence:
In some areas, near sites of prior human habitation, these species can be found in up to x5 the expected level.
Sadly, shortly after this contact there was a massive depopulation of the region as local people succumbed to Old World diseases for which they had no resistance.
Of course, none of this means we should value the amazing beauty, diversity & ecological function of Amazon any less.
In fact, the ability of nature to regenerate should give us hope.