A new archaeological study suggests between half a million to 1 million people resided in western Brazilian Amazonia before European arrival. The zone is centred on the State of Acre and extends into Rondônia and Amazonas.
The researchers, based in Helsinki, carried out essentially a meta-analysis of satellite imagery, combined with the authors’ own analysis. The imagery analysed spans 134,000 sq. km of Brazilian Amazonia.
The old settlements are revealed by earthworks, which are visible in analysis of satellite imagery. There are 1,279 sites recorded across the region of study.
The earthworks are typically bordered by a shallow ditch. The size, running for up to 400 metres, suggests collective labour and an organised polity.
Common earthworks in the study would have required an estimated 30,000 man-days of labour to construct. Many were also interconnected with further earthworks that constitute geoglyphs when they are viewed from the air.
Photo published by Martti Pärssinen.
Some of these mounds are topped by further mounds. A common formation is for the secondary earthworks, presumably for building construction, to surround a flat central plaza.
The oldest of these Acre earthworks date to as far back as 500BC. Five of the sites were occupied for 500 years, with the latest of them being still in use until the 14th century.
The earthworks have in fact been laid bare by deforestation. Acre, in Brazil’s west, is one of the hotspots for deforestation, the rates of which have been rising again after a lull following Bolsonaro’s 2022 election loss.
Acre’s findings echo a January 2024 finding of “low-density garden urbanism” in the Ecuadorian Amazon. This area was occupied between approximately 500BC and 600AD and featured mounds connected by roads running dozens of kilometres.
The “core” earthworks in this zone were “comparable in size to those of other great cultures of the past, such as Mexican Teotihuacan and Egypt’s Giza plateau.”
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