Not completely, but many sections of it were yeah. Some anthropologists have posited that humans played a major role in the transition towards jungle. Botanists know that you can't really explain the distribution of many plant species without the context of human culture. Some ecologists have even gone as far as to label Amazonia a "manufactured landscape" as we realize more and more how heavily the landscape was shaped by the 10+ million pre-Columbian indigenous people that lived there (I mean, this is the place that gave us potatoes, corn, tomatoes, peppers, sweet potatoes, beans, peanuts, etc. These people are plant experts!). At least as 10-12% of terra firme forests are anthropogenic in nature and many of the most common trees/plants are domesticated for human use.

No surprise why indigenous people are at the forefront of environmental defense movements. It's also one of the most dangerous place to be an environmental activist for this reason. 40% of all environmental defender murder victims are indigenous persons and 15% of all such killings happen in the Amazon