Archaeologists have identified nearly 400 previously unknown ancient earthworks in the southwestern Amazon, revealing evidence of complex societies in the region long before European contact. The findings, published recently in the journal Nature, suggest that large-scale landscape modification and significant population centers existed in the rainforest between approximately 600 B.C. and 850 A.D.
The discoveries were made possible through the use of lidar (light detection and ranging) technology, which allowed researchers to peer beneath the dense forest canopy near the border regions of Bolivia, Brazil, and Peru. The geoglyphs consist of a variety of geometric shapes, including circles and squares, linked by roads and composed of embankments, mounds, and trenches. Sizes vary, with most covering around 7 acres, featuring ditches up to 30 feet wide and 15 feet deep, while the largest spans over 120 acres.
Lead author Martti Parssinen, emeritus professor at the University of Helsinki, attributed the structures to an ancient multicultural society dubbed the Aquiry. Drawing on oral histories from the Apurinã Indigenous group living in the region, researchers believe the earthworks served multiple purposes, including festivities, political gatherings, ceremonies, dance, music, and competitive ball games. However, the exact usage remains uncertain. Archaeologists have found no evidence of permanent residential settlement associated with these sites, nor indications that they were constructed for defensive purposes.
The discovery challenges the longstanding perception of the Amazon as a largely pristine wilderness before European arrival in the 15th century. Historical accounts from the 16th century, such as those by the missionary Gaspar de Carvajal who accompanied Francisco de Orellana on his Amazon expedition, described densely populated areas with large, continuous settlements. For centuries, these narratives were dismissed due to the devastating impact of disease, colonization, and assumptions about the region's capacity to support complex societies without European-style agriculture.
Experts not involved in the study emphasized the significance of the findings. José Iriarte of the University of Exeter called the research "important and ambitious," highlighting the unprecedented scope of lidar coverage. Anna Roosevelt of the University of Illinois Chicago noted that while the geoglyphs' precise functions and meanings have yet to be fully understood, the evidence increasingly supports the existence of sophisticated pre-Columbian cultures that effectively managed and adapted to the rainforest environment.
The new data also suggests that at its peak, between 100 and 300 A.D., the Aquiry population may have reached up to three million across the surveyed region. However, some scholars urge caution with these estimates, as they are based on indirect measures, including the distribution of earthworks and the presumed labor required for their construction rather than extensive excavation of settlements.
Scientists warn that the fragile heritage of this area faces ongoing threats from deforestation driven by logging and agricultural expansion, including soybean farming. Eduardo Neves from the University of São Paulo noted that environmental destruction could irreparably damage or erase undiscovered sites. Researchers predict that thousands more earthworks may still lie hidden beneath the dense forest cover, some beyond the reach of current scanning technologies.
Together, these findings contribute to a growing body of research redefining the Amazon as a region shaped by extensive human activity, sophisticated social organization, and resilient cultural traditions long before European explorers arrived.