Surveys over the dense Amazon rainforest using canopy-penetrating lasers have revealed hundreds of vast structures built by a lost civilisation that thrived for almost 1500 years. The findings lend weight to suggestions that millions of people once lived in areas today regarded as wilderness.
The Aquiry civilisation, which lasted from roughly 600 BC to AD 850, built vast geometric earthworks, whose shapes may represent various deities, without using metal tools or animals. Many are also connected by ancient roads.
These people were little known to science until recent decades because the part of Amazonia where they lived constituted what had been thought to be 鈥渁n almost uninhabited pristine rainforest鈥�, says at the University of Helsinki, Finland. But researchers have been learning more about the civilisation鈥檚 extent using lidar, a laser-scanning technique that can create a three-dimensional map of the ground under most vegetation.
Advertisement
From aircraft flying over the forest, around 30 laser pulses are shot at the ground every square metre. Small gaps in the forest canopy allow some of these pulses to reach the terrain below and return to the aircraft.
In 2024, P盲rssinen and his colleagues flew over an area of nearly 4500 square kilometres, in the Brazilian states of Acre and Amazonas. The survey revealed 432 ditched geometric enclosures called geoglyphs, nearly 400 of which were completely new to science.
By extrapolating these results across the 183,000 square kilometres of territory inhabited by the Aquiry civilisation, the team estimates there may be as many as 30,000 geoglyphs.
On average, the earthworks cover 3 hectares, but they can be as large as 50 hectares. The ditches are typically about 12 metres wide and up to 5 metres deep. 鈥淭he scale and precision of these constructions is simply astonishing,鈥� says P盲rssinen.
Each of the average-sized geoglyphs would have required around 300 people to build and maintain, the researchers estimate. The findings suggest a total population of between 1.25 and 3 million people at the civilisation鈥檚 peak between AD 100 and 300, says P盲rssinen, and his feeling is that the upper end of the estimate is most likely.
鈥淭he notion of Amazonia as an untouched wilderness is largely a myth and [the truth is] that ancient human societies played an important role in shaping the present-day tropical rainforest,鈥� he says.
Over the past 20 years, P盲rssinen and his colleagues have excavated more than 40 ceremonial and settlement sites in Acre, Amazonas and Rond么nia (another Brazilian state), as well as in Bolivia.
This showed that the geoglyphs were ceremonial centres used as 鈥渧enues for gatherings, political decision-making and displays of chiefly generosity, ritual dancing, music, feasting, athletic competitions and ball games鈥�, he says. Long dwellings that housed several families were probably situated in a dispersed pattern around the earthworks.
The Aquiry had a major impact on the Amazon rainforest, says P盲rssinen, burning bamboo forest to make way for maize, squash and manioc, as well as clearing forests for the huge earthworks and the extensive roads leading to them. The Aquiry also grew many fruit-bearing tree species, including the Brazil nut tree and peach palm. It isn鈥檛 known what caused their demise.
at the University of Florida says the claims about population size are bold, but they are 鈥減lausible and extremely important, even mind-blowing鈥�.
鈥淭he idea of pre-Columbian urbanism in southern Amazonia has gained momentum over the past two decades. What we now need to know is what is going on around the detectable earthworks, such as occupational sites to support the high estimated population,鈥� he says.
at the National Institute of Amazonian Research in Manaus, Brazil, says the new research 鈥減uts a large-scale culture in the Amazon forest鈥�.
鈥淣eedless to say, they have not ground-truthed the entire set of new geoglyphs, but previous lidar studies have been remarkably efficient, so I feel that their numbers are solid,鈥� he says.
Nature
