Archaeologists have discovered a collection of lost cities in the Amazon rainforest that were home to at least 10,000 farmers about 2,000 years ago.
A series of mounds and buried roads in Ecuador were first discovered more than two decades ago by archaeologist Stéphen Rostain. But at the time, “I wasn't sure how it all fit together,” said Rostain, one of the researchers who reported the discovery Thursday in the journal Science.
Recent mapping using laser sensor technology revealed that these sites were part of a dense network of settlements and roads hidden in the forested foothills of the Andes that lasted about 1,000 years.
“It was a lost valley of cities,” said Rostain, who leads research at France’s National Center for Scientific Research. “It's incredible.”
This LIDAR image provided by researchers in January 2024 shows complexes of rectangular platforms arranged around low plazas and distributed along wide dug roads at the Kunguints site in Ecuador's Upano Valley. Antoine Dorison, Stéphen Rostain / AP
The settlements were built between around 500 BC. Inhabited by the Upano people between 300 BC and 300 to 600 AD – a period roughly contemporaneous with the Roman Empire in Europe, the researchers found.
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Residential and ceremonial buildings built on more than 6,000 mounds were surrounded by agricultural fields with drainage canals. The largest roads were 33 feet wide and stretched 6 to 12 miles.
Although it is difficult to estimate populations, at least 10,000 people lived on the site – perhaps as many as 15,000 or 30,000 at its peak, said archaeologist Antoine Dorison, co-author of the study at the same French institute. That's comparable to the estimated population of Roman-era London, then Britain's largest city.
“This shows a very dense settlement and an extremely complex society,” said archaeologist Michael Heckenberger of the University of Florida, who was not involved in the study. “For the region, it’s really in a class of its own when it comes to early times.”
José Iriarte, an archaeologist at the University of Exeter, said it would have taken a sophisticated system of organized labor to build the roads and thousands of mounds.
“The Incas and Mayans built with stone, but the people of Amazonia typically didn't have access to stone to build with – they built with clay. It’s still an immense amount of work,” said Iriarte, who was not involved in the research.
The Amazon is often viewed as a “pristine wilderness with only small groups of people.” But recent discoveries have shown us how much more complex the past actually is,” he said.
Scientists have also recently found evidence of complex rainforest communities that existed before European contact in other places in the Amazon, including Bolivia and Brazil.
“There has always been an incredible diversity of people and settlements in the Amazon, not just one way of life,” Rostain said. “We’re just learning more about them.”