An international research team has identified evidence of a far larger pre-Columbian society in southwestern Amazonia than previously documented, using airborne laser mapping to detect hundreds of structures beneath forest cover. The study, reported on Wednesday in Nature, estimates that 24,000 to 30,000 earthworks may lie across the wider region, with about two-thirds associated with the Aquiry cultural tradition.
Researchers mapped about 4,500 square kilometres by aircraft in 2024 and combined those LiDAR results with satellite imagery, known archaeological sites and surveys of deforested land. Laser pulses that reached the ground allowed the team to build terrain models below the canopy, revealing geometric enclosures, ceremonial centres and roads that ordinary aerial photographs could miss.
According to El País and the University of Helsinki, the team defined an Aquiry-associated territory of at least 183,000 square kilometres near the modern borders of Brazil, Bolivia and Peru. Its southern limits extended between sites in Rondônia and Acre in Brazil, the Riberalta area of Bolivia and Puerto Maldonado in Peru. The culture is thought to have shaped this landscape from roughly 600 BCE to 850 CE.
The researchers found substantially more earthworks in directly examined deforested areas than satellite surveys alone had recorded. Many features are large squares, circles, octagons or more complex enclosures, bounded by ditches as deep as five metres and raised banks. Roads linking sites indicate organized movement and interaction rather than isolated settlements.
To estimate population, the team calculated the labour needed to build and maintain the structures with wooden tools, assuming an adult could move about one cubic metre of earth per day. On that basis, it estimated an average community of around 300 people per structure and a peak regional population between 1.25 million and 3 million around 100 to 300 CE. The authors stress that these figures are modelled ranges, not a direct census.
The findings strengthen evidence that parts of Amazonia were densely occupied and deliberately managed long before European contact, challenging older portrayals of an untouched wilderness inhabited only by small, scattered groups. Researchers say field verification and dating of more sites remain essential, while the scale of the record suggests that intact forest may still conceal many structures and ecological legacies of Indigenous land management.
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