They find pre-Columbian urban centers in the Amazon

A team of scientists has concluded that mysterious mounds in the southwestern corner of the Amazon Basin were once ancient urban settlements. Using a remote sensing technique used to map the terrain from the air, they found that for about 1,500 years, ancient Amazonian cultures built and lived in a series of densely populated urban centers. In them rose pyramids of earth 22 meters high and were surrounded by kilometers of elevated roads.

The complexity of the settlements is “fascinating,” says Heiko Prümers, a member of the team and a researcher at the Berlin-based German Archaeological Institute.

“This is the first clear evidence that urban societies existed in this part of the Amazon basin,” explains Jonas Gregorio de Souza, an archaeologist at Pompeu Fabra University. The study adds to a growing body of research suggesting that the Amazon was home to advanced societies long before the arrival of Europeans and was therefore not as wild and pristine an area as once thought. The discovery was published on May 25 in Nature.

New perspective

Man has inhabited the Amazon basin, a vast river drainage system about the size of the United States, for about 10,000 years. The research community believed that, before the arrival of Europeans in the 16th century, all indigenous Amazonians lived in small nomadic tribes that had little influence on the world around them. However, although early European visitors described a landscape dotted with towns and villages, later explorers never found such settlements.

In the 20th century, archaeologists had not yet confirmed their existence, arguing that the nutrient-poor soil of the Amazon was unable to support large-scale agriculture, which would have prevented the rise of tropical civilizations similar to those found in Central America and Southeast Asia. However, in the 2000s, archaeologists began to change their minds. Some researchers suggested that the unusual concentration of crop plants, as well as some particularly nutrient-rich soils that could have been created by man, might indicate that ancient Amazonian peoples had modified their environment.

The hypothesis gained strength in 2018, when archaeologists found hundreds of large mounds of geometric shapes that had been uncovered as a result of deforestation in the southern Amazon jungle. The structures suggested ancient organized societies, capable of thriving in one place for years. However, direct evidence of settlement was lacking.

In 1999, Prümers began studying a set of mounds in the Bolivian Amazon region, outside of thick tropical forest. In that area, a multitude of tree-covered hills rise above plains that are flooded in the rainy season.

Previous excavations had revealed that such “forest islands” contained remnants of human settlement, including some remnants of the mysterious Casarabian culture, which appeared around AD 500 At one of the sites, Prümers and his collaborators identified what appeared to be a wall , which pointed to a permanent settlement. The researchers also found tombs, platforms and other signs of a complex society. But the dense vegetation made it difficult to use conventional methods to examine the site.

what lies beneath

In the 2010s, the use of lidar, a remote sensing technique that uses a laser beam to generate three-dimensional images of the ground, became widespread in archaeology. In 2012, a study carried out with lidar in a valley in Honduras allowed the discovery of an ancient pre-Columbian city whose existence had not yet been proven. The settlement had been completely engulfed by jungle since it was abandoned in the fifteenth century, making it nearly impossible to see from the air without the aid of lidar.

In 2019, Prümers and his collaborators flew in a helicopter equipped with a lidar device over six areas near sites that were known to have been occupied by the Casarabes. The findings exceeded the team’s expectations: Lidar revealed the size and shape of 26 settlements, including 11 that the researchers weren’t looking for, a monumental task that would have taken 400 years to complete with conventional methods, says Prümers.

Two of the urban centers each covered an area of ​​more than 100 hectares, three times the size of Vatican City. Lidar images revealed walled enclosures with wide terraces rising 6 meters above the ground. At one end of the terraces stood conical pyramids of earth. Most likely, people lived around these terraces and moved along the causeways that connected the settlements.

“We think of the Amazon as a green desert,” repairs Prümers. But if civilizations arose and prospered in other tropical regions, “why shouldn’t something similar exist here?”

mysteries to solve

The reasons why the settlements were abandoned after 900 years remain an enigma. Radiocarbon dating has revealed that the Casarabe disappeared around the year 1400.

Prümers points out that the lidar images revealed the existence of water deposits in the settlements, which would imply that this part of the world was not always wet, an environmental change that could have caused population migration. However, the pollen data record shows that corn was grown continuously in the area for thousands of years, an indication of sustainable agricultural practices.

In any case, the discovery of long-lost Amazonian societies “changes the general perspective of Amazonian archaeology,” says Eduardo Neves, an archaeologist at the University of São Paulo. According to the expert, there is no doubt that current logging and agriculture are destroying important archaeological sites that have not yet been discovered, but the growing interest in Amazonian archeology could perhaps lead to the protection of vulnerable places.

The recent discoveries also contradict the idea that indigenous peoples were passive inhabitants of the Amazon basin before the arrival of Europeans. “The populations that lived there changed the landscape forever,” concludes Neves.

freda kreier

Article Translated and adapted by Research and Science with permission from Nature.

Reference: “Lídar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon». Heiko Prümers et al. in NatureMay 25, 2022.

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