An aerial laser survey published in Nature has confirmed that the Aquiry civilisation LiDAR discovery reshapes everything previously understood about precolonial life in the southwestern Amazon, tripling the estimated territory of this monument-building culture from roughly 60,000 km² to approximately 183,000 km².
The survey, conducted in 2024 over 4,430 km of flight paths and covering 4,497 km² in the Brazilian states of Acre and Amazonas, yielded 432 separate earthworks. Of those, 396 were previously undocumented, clustered around the cities of Rio Branco, Lábrea, Boca do Acre, and Carauari. By extrapolating these results alongside existing satellite data, the authors suggest the region may contain between 24,000 and 30,000 earthworks in total.
What LiDAR Found Beneath the Canopy
The tool making this possible is LiDAR, short for Light Detection and Ranging. It fires a laser that passes through the jungle canopy, reaches the ground, and rebounds back to the aircraft, working on a principle similar to sonar. The technology allows researchers to map terrain beneath dense vegetation in fine detail, and has driven a series of large-scale discoveries across the Amazon over the past two decades.
Leading the survey was Martti Pärssinen, an archaeologist at the University of Helsinki, working alongside colleagues from Finland and Brazil, according to Live Science. The structures they mapped are known as Amazonian geoglyphs: geometric ditched enclosures composed of earthen embankments. They range from 0.35 to 14 hectares in size, with the largest known example covering nearly 123 acres. They are assumed to have functioned as ceremonial, political, and public gathering centres, though direct evidence of daily life remains thin.
‘On the basis of both existing data and our LiDAR documentation, we show that this cultural area alone contains as many earthworks as previously estimated for the whole of Amazonia,’ the authors wrote in their paper.
A Population Rivalling the Mayan World
The human scale of the Aquiry civilisation is where the numbers become genuinely arresting. According to BBC Science Focus Magazine, the Aquiry lived in the region from roughly 600 BCE to 850 CE, first beginning to construct the geoglyphs around 2,500 years ago. The civilisation is believed to have reached its greatest scale and wealth between the 1st and 4th centuries CE, with a successor society continuing to build and use the earthworks, albeit with changes in style, as late as the 13th century.
An earlier population estimate, based on the labour required to build and maintain around 200 known earthworks, put the figure at roughly 60,000 people. With the evidence base now vastly larger, the authors of the Nature paper have revised that figure sharply upward. ‘We also propose that the total human population of the area in 100–300 CE was 1.25–3 million people,’ they wrote. That range would place the Aquiry on a demographic par with Late Preclassical Mayan societies spanning from the northern Yucatan Peninsula to Belize, making Aquiry one of the largest populations in the Americas at the time.
If projections of 28,000 or more earthworks hold, the spatial extent of the Aquiry region would not be far behind the Maya Lowlands either.
Abandonment and What Remains Unknown
For all the scale now being revealed, the gaps remain considerable. The Aquiry are known almost exclusively through their earthworks; almost nothing is understood about their language, governance, trade networks, or the details of everyday life. The structures themselves offer only partial answers.
According to Smithsonian Magazine, the geoglyphs appear to have been abandoned for good between 850 and 950 CE, a relatively narrow window that raises its own questions: whether the abandonment was gradual or abrupt, and what drove it, remains unknown.
The concentration of earthworks is itself a challenge to comprehend. The authors note that the surveyed area, representing just 3% of the Amazon, holds a greater density of these structures than the other 97% combined. The survey covered only a fraction of the area where earthworks may exist, meaning the current figures, however large, are likely still an undercount. The next phase of survey work will determine whether the outer bounds of Aquiry territory, now set at approximately 183,000 km², hold up or expand further still.
