Newly Unearthed Ancient Amazonian Geoglyphs Change What We Knew About Civilization Here


An aerial photo of one of the "earthworks" shows its geometric shape. University of Exeter.

Tucked away in the remote Amazonian rainforest away from major rivers, researchers have unearthed the remains of hundreds of fortified villages built before the arrival of Europeans. Made up of different communities speaking a variety of languages, researchers believe the area was home to as many as 10 million people before Columbus arrived.

Understanding how these societies impacted their environment thousands of years ago could help inform how we handle policy and sustainability concerns today.


Archaeologists from the University of Exeter discovered 81 earthworks called geoglyphs – human-made ditches with square, circular, or hexagonal shapes – along 1,800 kilometers (1,120 miles). They are believed to have been continuously occupied by “earth-building cultures living in fortified villages” from 1250 until 1500 AD, filling a gap in archaeological history. Experts don’t know what these structures were used for, but think they could have been for ceremonial rituals. Villages were often nearby, inside, or connected through these structures by a network of causeways.

Typical position of ditched enclosures on plateaus overlooking rivers. These ditces are outlined in black and mounds/walls outlined in white. (Satellite image ©2018 Google, DigitalGlobe)

They’re part of a bigger network of an estimated 1,300 geoglyphs across 400,000 square kilometers (154,400 square miles) in southern Amazonia, and challenge what we thought we knew about ancient civilizations here. Researchers say these geoglyphs were probably made during seasonal droughts by clearing forests, which means humans have been influencing their environment in bigger ways for much longer than previously believed. Because they’re tucked away from major rivers, it means large communities were spread across various landscapes.

"There is a common misconception that the Amazon is an untouched landscape, home to scattered, nomadic communities. This is not the case,” said Dr Jonas Gregorio de Souza, who was part of the study, in a statement. “We have found that some populations away from the major rivers are much larger than previously thought, and these people had an impact on the environment which we can still find today.”

The nature and scale of Pre-Columbian land use in the area continues to be a debated issue. A lot remains to be uncovered, considering only about one-third of the sites have been found and 95 percent of the interfluvial forests are still unexplored.


"Our research shows we need to re-evaluate the history of the Amazon. It certainly wasn't an area populated only near the banks of large rivers, and the people who lived there did change the landscape,” said Professor Jose Iriarte, who was also part of the study. “The area we surveyed had a population of at least tens of thousands.”

Archaeologists say understanding the role humans played in shaping these landscapes and understanding the forests’ resilience can help modern society better understand how to make informed policy decisions on sustainable futures.

"The Amazon is crucial to regulating the Earth's climate and knowing more about its history will help everyone make informed decisions about how it should be cared for in the future," said de Souza.

The study was published in Nature Communications

Distribution of earthworks in across sites in the Amazon. Courtesy of Nature Communications.

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