Laser scanning of the Amazon rainforest has uncovered hundreds of ancient earthworks belonging to a lost civilization that may once have been home to up to 3 million people, according to New Scientist.
In 2024, Martti Pärssinen of the University of Helsinki and his colleagues surveyed nearly 4,500 square kilometers in the Brazilian states of Acre and Amazonas using LiDAR, a technology that maps terrain beneath vegetation. They identified 432 geometric earthen structures called geoglyphs, nearly 400 of which were previously unknown to science.
The structures were built by the Aquiri civilization, which existed from roughly 600 BCE to 850 CE. The builders used no metal tools or draft animals, and many of the geoglyphs are linked by ancient roads. The average structure covers about 3 hectares, though some reach 50 hectares, with surrounding ditches about 12 meters wide and up to 5 meters deep.
Pärssinen said the scale and precision of the structures were remarkable. Based on the survey, researchers estimate that as many as 30,000 such geoglyphs may exist across the 183,000 square kilometers the civilization once occupied.
At its peak, roughly between 100 and 300 CE, the population is estimated to have ranged from 1.25 million to 3 million. Pärssinen said the upper figure was the most likely.
He also said that the idea of the Amazon as untouched wilderness is largely a myth, arguing that ancient societies played a major role in shaping the modern rainforest. The civilization cleared land for corn, squash, and cassava, and cultivated fruit trees including Brazil nuts and peach palms. The reasons for its disappearance remain unknown.
Michael Heckenberger of the University of Florida called the population estimates plausible and extremely important, saying researchers now need to find more settlements around the known earthworks to confirm the figures.
