Ancient indigenous people built hundreds of large and mysterious earthworks in the Amazon rainforest more than 2,000 years ago.

More Than 450 Earthworks Found In Amazon Rainforest

Researchers have discovered over 450 earthworks in the western Brazilian Amazon after flying drones over the area. The large geometrical geoglyphs in Acre, a state in northwestern Brazil within the Amazon rainforest, were built by indigenous people more than 2,000 years ago before the arrival of the Europeans.

Geoglyphs are large designs produced on the ground and are often formed by rocks or similarly durable elements of the landscape such as trees, gravel, earth, and stones.

The geoglyphs were hidden by trees for most of their history, but deforestation has eventually helped reveal their presence. The discovery provided evidence how the ancient people lived in the region prior to the arrival of European people.

Discovery Challenges Idea That Amazonian Forests Are Pristine Ecosystems

Study researcher Jennifer Watling, from the University of Sao Paolo's Museum of Archaeology and Ethnography, said that the fact the sites were hidden beneath mature rainforest for centuries challenges the notion that the Amazonian forests are pristine ecosystems.

Researchers wanted to know the extent to which the ancient people impacted the landscape to make way for the earthworks. Using state-of-the-art methods, the researchers reconstructed 6,000 years of vegetation and fire history around two enclosure sites and found that humans heavily altered bamboo forests and made clearings to build the geoglyphs.

Alterations Made But Not On A Grand Scale

Although analysis hinted that the land around the geoglyphs was altered for thousands of years, the researchers said that the alterations did not involve clearcutting or field burning. Small clearings were instead made to allow the creation of the earthworks. The indigenous people also altered the forests by encouraging the growth of preferred species.

"We show that bamboo forest dominated the region for ≥6,000 y and that only small, temporary clearings were made to build the geoglyphs; however, construction occurred within anthropogenic forest that had been actively managed for millennia," Watling and colleagues wrote in their study published in PNAS.

"In the absence of widespread deforestation, exploitation of forest products shaped a largely forested landscape that survived intact until the late 20th century."

Possibly Served As Ritual Sites

Since few artifacts have been recovered from the earthworks, the researchers do not think that the buildings were used as shelter or village. The sites possibly served as gathering places that had spiritual significance. The sites also appear to have been managed with refined ecological awareness.

Watling also said that the sites resembled Neolithic causewayed enclosures found at sites such as the Stonehenge.

"It is interesting to note that the format of the geoglyphs, with an outer ditch and inner wall enclosure, are what classicly describe henge sites. The earliest phases at Stonehenge consisted of a similarly layed-out enclosure," Watling said.

Watling added that despite evidence showing that the Amazonian forest was managed by ancient people before European contact, this should not be used to justify the destructive and unsustainable use of land practiced today.

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