A laser survey of the southwestern Amazon has mapped 432 geometric earthworks beneath the forest canopy. Only 36 of them were documented before. Writing in the journal Nature, the authors conclude that the pre-colonial society which built them occupied an area roughly three times larger than archaeologists assumed.
The work was led by Martti Pärssinen of the Ibero-American Institute of Finland, with Finnish and Brazilian colleagues. The team flew lidar surveys over 4,497 square kilometres around the Brazilian towns of Rio Branco, Lábrea, Boca do Acre and Carauari, in the states of Acre and Amazonas, the Good News Network reports. Lidar sends laser pulses through gaps in the canopy and times their return. The result is a detailed map of the ground below.
Extrapolating from the surveyed strip, the researchers estimate that 24,000 to 30,000 earthworks and related features lie in the wider region. About two thirds are attributed to the culture the authors call the Aquiry, according to The Art Newspaper.
Ditches, embankments and roads
The Aquiry flourished from roughly 600 BC to AD 850 across some 183,000 square kilometres of what is now Brazil, Bolivia and Peru. They dug deep ditches, raised high embankments and linked some sites by roads. They lived in multifamily longhouses and farmed maize and squash. The enclosures served ceremonies and political gatherings rather than defence. Their sites were abandoned between AD 850 and AD 950. New population estimates put 1.25 million to 3 million people in the area at its peak, between AD 100 and AD 300.
That undercuts the old picture of a thinly settled wilderness. Pärssinen first saw such structures in 2002, on deforested land outside Rio Branco, after the archaeologist Alceu Ranzi invited him to Acre. Soils there were then thought too poor to support large or complex societies. Lidar, he told The Art Newspaper, has now delivered a second such moment by revealing what stands under the canopy.
The Aquiry also shaped the forest itself. They managed and domesticated useful trees, among them the Brazil nut and palms such as peach palm and uricuri, Pärssinen said. José Miguel Pérez-Gómez, a Venezuelan archaeologist not involved in the study, cautioned against the language of lost worlds. The survey reveals "a form of civilisation that Western perspectives had failed to recognise," he said. Tens of thousands of the predicted structures have still to be mapped.