The sentence that best supports the central idea that Remate de Males was mostly uninhabited is:
"Some thirty years ago, a prospector with his family and servants arrived at this spot near the junction of the Javary and the Itecoahy rivers, close to the equator."
This sentence implies that prior to the arrival of the prospector and his family, the area was largely uninhabited, highlighting the remoteness and wilderness of the location.