20,000 Ancient Amazon Earthworks Challenge Views on Precolonial Societies and Forest Conservation

A July 2026 Nature study documents over 20,000 precolonial earthworks — large ground designs called geoglyphs — across the Southwest Amazon, radiocarbon-dated to roughly 2,500 years old. The scale challenges the view that the basin could not sustain large, complex societies, complicates conservation models treating the forest as pristine, and may affect Indigenous land-rights discussions.