Ancient Amazon people cleared swathes of forest to build enormous earthworks similar to those at Stonehenge, researchers have discovered.
Deforestation has uncovered traces of more than 450 earthworks in the western state of Acre that were previously concealed by a dense canopy of trees.
Around 1,200BC, the forest's inhabitants began creating massive geometric shapes in the forest floor using ditches up to 36ft wide and 13ft deep, a style of earthworks known as "geoglyphs".
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Although the ditches at Stonehenge pre-date those in Acre by about 2,500 years, researcher Dr Jennifer Watling believes these new finds served a similar purpose in Amazonian society.
"It is likely that the geoglyphs were used for similar functions to the Neolithic causewayed enclosures, i.e., public gathering, ritual sites," she told the Daily Telegraph.
Watling's team used cutting-edge technology to analyse soil samples, enabling them to reconstruct 6,000 years of plant life in two of the enclosures.
"They found that humans heavily altered bamboo forests for millennia and clearings were made to build the geoglyphs," the Telegraph reports.
Charcoal traces in the samples indicated the Amazonians cleared space for the earthworks by setting fires. The analysis also found that after humans began to actively manage the landscape, palms replaced bamboo as the predominant tree in the forest.
This supports the theory that Amazonian rainforests "once thought to be pristine wildernesses" were actively managed by their inhabitants prior to contact with Europeans, says Popular Archaeology, "challenging the apparent vulnerability of Amazonian forests to human land use".
"There's been a very big debate circling for decades now about how pristine or man-made the Amazonian forests are," said Dr Watling. However, she stressed that the discovery "should not be cited as justification for the destructive, unsustainable land-use practised today".
Instead, it should "highlight the ingenuity of past subsistence regimes" and "the importance of indigenous knowledge for finding more sustainable land-use alternatives".
