Remains of vast ancient cities have been found in the Amazon

The Amazon Valley looked like so many others, with a muddy river winding through dense forest, except it had earthen hills rising at distinct right angles and ditches that carved long straight lines into the ground.

In this rainforest, archaeologists say, lie the bones of vast ancient cities: earthworks that were once roads, canals, squares and platforms for houses where thousands of people had lived for centuries, long before Europeans ever attempted to map South America.

The cluster of interconnected cities was only recently mapped in the Upano Valley in eastern Ecuador, a research team reported this month in the journal Sciencebringing decades of research and laser mapping technology that have helped revolutionize archaeology.

The technology, called lidar, allowed researchers to pierce the forest cover and map the ground beneath it, documenting five major settlements and ten secondary sites over an area of ​​more than 185 square kilometers.

Radiocarbon dating has shown that humans lived there from about 500 BC to about 300 AD and 600 AD, making the settlements among the oldest yet found in the diverse landscapes of the Amazon.

“It's a huge contribution to the archeology of the Amazon,” says José Iriarte, an archaeologist at the University of Exeter who was not involved in the study.

This region, where the Amazon reaches the eastern slope of the Andes, has long been seen as an area “where nothing really happens there,” he said.

Now, he said, “we have a big, idiosyncratic cultural development.”

Stéphen Rostain, the study's lead researcher, said he was impressed by the complexity of the cities and the amount of work required to build them.

The “perfectly straight roads” that connected them were a sign of the cities' sophistication, he said, adding that they would have needed engineers and workers, farmers to provide food, and some kind of chairman, chief or king to lead “a specialized and stratified society.”

The original construction was done by groups from the Kilamope and later Upano cultures, the researchers said, adding that people of the Huapula culture lived in the area between 800 and 1200.

The team unearthed artifacts including painted pottery and jugs containing the remains of the traditional chicha, the corn-based drink that remains a mainstay of the Andean region today.

Although archaeologists have long known of earthworks in the area, lidar – which pierces leaves with laser pulses from aircraft and has helped find hidden Mayan sites and ancient Cambodian cities – revealed the extent of the settlements.

Ultimately, they mapped more than 6,000 earthen platforms, connected by roads and spread across a landscape shaped to control water and grow crops.

The researchers determined that some of the earthen mounds were residential platforms, and said in the paper that other, larger complexes may have served a “civil ceremonial function.”

Particularly striking, archaeologists said, were the systems of roads and agriculture – how ancient people diverted heavy rainfall along the eastern slopes of the Andes to take advantage of the fertile volcanic soil.

“It really shows us that there are many more ways to live in the Amazon in the past than we thought in archaeology,” said Eduardo Neves, an archaeologist at the University of São Paulo who was not part of the team.

He said the research added to growing evidence that the Amazon was “densely populated by indigenous peoples for thousands of years, in very large settlements.”

The new paper also builds on research showing the extent to which ancient humans transformed their landscapes, archaeologists said.

“This idea of ​​some sort of pristine, pristine landscape in the Amazon was absolutely not the case,” says Jason Nesbitt, an archaeologist at Tulane University.

That long-standing idea, the archaeologists said, was fueled in part by the way indigenous populations were decimated by the arrival of Europeans and by the Amazon's resources. The ancient people there did not have enormous amounts of stone to work with, like the monument builders of Central America or Peru, and instead used the available land.

Agricultural modifications in parts of the Amazon have “long pointed to large populations there in the past,” according to Simon Martin, an anthropologist at the Penn Museum in Philadelphia.

Amazonia remains “the only extensive site that may still harbor hidden archaeological wonders,” he said.

Dr. Nesbitt added that while it was difficult to estimate the population of an ancient settlement, the researchers' suggestion that as many as 30,000 people had once lived in the Upano Valley seemed reasonable.

“It's a very exciting time to be doing archeology in the Amazon because of the use of lidar,” added Dr. Neves added. “Places that were already known are being re-examined and places that were not yet known are being mapped for the first time.”

The archaeologists expressed hope that more excavations would be done in the valley and that the work could help answer many of the outstanding questions about the people who lived there, including their beliefs, their system of government and what connections they may have had have with other societies. had.

“We can learn a lot from the human past,” said Dr. Rostain. The size and complexity of the cities showed that the inhabitants were more than “hunter-gatherers lost in the rainforest looking for food.”

Dr. Neves added that continued research could help protect the Amazon from the threat of deforestation.

“Some of the destruction is based on the idea that the Amazon has never really been inhabited in the past, that there has never been many people, that it is there for the taking,” he said. “I think this kind of work, archeology in general, and this kind of research is very important because it adds to the evidence that shows that the Amazon was not an empty place.”