My randomly rolled location is apparently almost dead on the city of Itaituba, which was founded in 1974 or thereabouts as a gold-mining boomtown. So I can put some gold in the novel. There is also an enormous mass of rapids a short distance upstream, so where I have already put the enemy tribe, so it provides a good way to make their village relatively close but also relatively accessible...
Helpfully for my licence to make stuff up, I have found that basically nothing is known about who was living there in 1456 BCE: the best places for agriculture are on the floodplains, where the soil is constantly renewed, and historically that is where almost all the people in the Amazon basin have lived- and their pots and stuff eventually get washed away with minor course corrections of the rivers. Interestingly a lot of cultivated plants (manioc, peanuts, the whole capsicum/chile complex, pineapple, avocado...) were first domesticated in the Amazon basin prior to 2000 BCE and appeared in Peru and on the Carribean Coast pretty much as they exist today, without any ancestral forms- so there was some lost civilisationing going on somewhere. The general location I randomly rolled has also been postulated as the source of the speakers of the Tupi-Guarani language family, at around my randomly rolled time. Someone in Wisconsin has written a PhD thesis attempting to reconstruct Proto-Tupi-Guarani, so I will try to get hold of it.
I have also learned that the Trans-Amazon highway, which scythes so dramatically across the continent in my atlas, no longer exists; it was built in the 1970s but was too expensive to maintain, so huge lengths of it have already turned into secondary growth forest.
