Groundbreaking Study Debunks a Myth About Ancient Amazonian Societies

The Amazon rainforest is often imagined as a pristine, dense jungle, untouched by humans. But that’s largely a myth: Indigenous societies have lived in the forest for more than 12,000 years. And now, a new study suggests ancient Amazonians left a far bigger footprint in the forest than previously thought.

More than 10,000 previously undiscovered archeological sites may be hidden beneath rainforest canopy, researchers report Thursday in the journal Science. The evidence of past human settlements, called earthworks, were revealed by analyzing and extrapolating remote sensing data.

“We were really surprised that there are so many more sites to be discovered,” said Carolina Levis, an ecologist at the Federal University of Santa Catarina in Brazil and study co-author. “It would take many lives to understand the ancient history of this region, because it’s so big and so diverse.”

Finding ancient sites in the Amazon is difficult, as much of the forest remains remote and veiled by trees. Scientists have spotted some settlements using satellite imagery, which can reveal evidence of people having moved the earth around to create ditches, ponds, wells and ceremonial structures. But this only really works in deforested areas — that raised the possibility there were many more hidden from view.

To peer under the canopy and find out, Levis and her team used a technology called LIDAR, which beams lasers down from aircraft to map the small changes in the topography of the forest floor. They analyzed data from over 2,000 square miles of forest and found 24 previously unreported earthworks across the Amazon.  

These sites included ringed structures that might have been ceremonial or defensive, fortified villages, mountaintop settlements, road networks, and even megalithic structures akin to Stonehenge, said Levis. 

But the area covered by this LIDAR survey represented just a small slice of the Amazon, about 0.08% of the total forest. To get a broader look, the team put their LIDAR data and other previously identified sites into a statistical model that predicted where undiscovered sites might be, based on over 40 variables including temperature, water availability and soil structure.

The model found that between 10,272 and 23,648 sites remain undiscovered, suggesting that currently documented sites account for a tiny fraction of what may be out there. The predicted sites were mostly concentrated in southwestern Amazonia, where there’s existing evidence of earthmoving communities connected by roads. But the model also predicted sites in less well studied areas across much of the forest. 

The researchers also found evidence that many of these sites co-occurred with domesticated plant species, including fruit and nut trees, suggesting that these societies shaped local ecosystems to support their communities.

“There was a kind of small-scale urbanism in the Amazon — political centers connected with small villages surrounded by managed forests,” said Levis. “They used the land in a way that didn’t destroy the forest, like we’re seeing today, but managed it so that it keeps providing services,” she said. “We have a lot to learn from them.”