For hundreds of years, the Amazon rainforest concealed over 450 massive, mysterious earthworks similar to those in Stonehenge. As a result of deforestation, researchers were able to catch a glimpse of the baffling geometrical geoglyphs in Brazil’s Acre state. The 2,000-year-old earthworks reveal a wealth of information we didn’t know before about how ancient people managed the rainforest.

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Many people used to think the Amazon rainforest ecosystem remained largely untouched by humans in the past, an idea challenged by the recent discovery of these huge earthworks. Led by Jennifer Watling of the University of São Paulo and the University of Exeter, a team reconstructed fire and vegetation history over 6,000 years near two of the geoglyphs, and found humans actually changed the bamboo forests heavily for millennia. They temporarily cleared areas to build the earthworks.

Related: Archaeologists reveal fresh details about 4,500-year-old “New Stonehenge”

As researchers didn’t find many artifacts around the earthworks, the sites probably weren’t villages, and their layout prompts researchers to think they weren’t used for defense. Instead, the ancient geoglyphs may have been utilized only once in a while for ritual gatherings.

Watling cautions against excusing rampant deforestation based on this new information. Her team’s research shows while ancient people altered the rainforest, they did not employ long term, large-scale deforestation as happens today, or burn swaths of forest. Instead they employed ancient agroforestry practices and focused on economically valuable trees like palms to create what the University of Exeter describes as a prehistoric supermarket of products from the forest.

Watling said, “Our evidence that Amazonian forests have been managed by indigenous peoples long before European Contact should not be cited as justification for the destructive, unsustainable land-use practiced today. It should instead serve to highlight the ingenuity of past subsistence regimes that did not lead to forest degradation, and the importance of indigenous knowledge for finding more sustainable land use alternatives.”

Nine other researchers from institutions in Brazil, the United Kingdom, and Canada joined Watling in the research; the journal Proceedings of the National Academy of Sciences published their study online this month.


Images via Jenny Watling/