Laser scans prove large settlements in the Amazon rainforest

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The settlements in the Amazon basin, which are around 1500 years old, disprove the myth that the indigenous people lived as hunter-gatherers in an untouched wilderness before the arrival of the Spanish conquerors.

Laser scans prove large settlements in the Amazon rainforest 1

Sometimes history has to be rewritten: Until a few years ago, researchers assumed that the inhabitants of the Amazon basin in pre-Hispanic times roamed the dense greenery in small groups as hunter-gatherers, without exerting much influence on their environment.

This was a misconception: researchers from Germany and England have now been able to prove, thanks to the new Lidar (Light Detection and Ranging) technology, that large settlements rose from the vast plains in the southwestern Amazon basin even before the arrival of the Spanish conquerors.

In the center of one of the settlements, there was even an earth pyramid about 22 meters high on a 22-hectare, artificially constructed terrace almost 4 meters high. The settlements in the Bolivian lowlands of Llanos de Mojos were surrounded by massive defensive fortifications, and they were connected by kilometers of flood-proof causeways.

Area long thought to be uninhabited

The “incredibly complex settlements” were discovered by a team of archaeologists led by Heiko Prümers of the German Archaeological Institute. The results were recently published in the scientific journal “Nature.”

According to Prümers, the decisive factor for science is where exactly these large settlements were found, because they refute the current doctrine: “We are here in a marginal area of Amazonia, in a zone that, at least in the last 50 years, has been considered relatively uninhabited by science. And when you suddenly find large settlements covering more than 100 hectares, then of course it’s a bit of a sensation,” says archaeologist Prümers enthusiastically in an interview with DW.

Evidence of extensive settlements

The entire Amazon basin is roughly the size of Europe: from Portugal to the Urals. There is evidence that people have lived there for more than 10,000 years. The current research results now prove beyond doubt that the Amazon inhabitants did not simply live in and from the untouched wilderness, but already fundamentally changed their environment through settlement structures.

Dr. Heiko Prümers Deutsches Archäologisches Institut
Dr. Heiko Prümers of the German Archaeological Institute

Although there were reports from the first European travelers of sunken cities in the jungle, decisive evidence was lacking for a long time.

It was only a few years ago that large mounds were discovered in the rainforest during clearing and expeditions, suggesting that people had lived there for a long time.

Heiko Prümers has been researching some of the 150 or so settlements known so far since 1999, finding them where the impact of recurrent flooding during the rainy season is lowest. “People sought out regions where there weren’t regular problems with major flooding, and that’s where they settled for a long time,” Prümers explains.

Settlement long before the arrival of the Spanish
So long before the Spanish conquistadors discovered South America for themselves in the 16th century, people of the Casarabe culture were already building settlements, including unusually large ones like that of Cotoca, between 500 and 1400 AD.

Archäologisches Team vor Helikopter
Vom Helicopter aus machte die Lidar-Technik insgesamt 26 Siedlungen sichtbar, 11 noch nicht entdeckt worden waren called von.

Until now, however, the full extent of the large settlements could only be guessed at under the dense vegetation. The breakthrough came with lidar technology, in which a laser attached to a helicopter or airplane scans the overgrown area.

Because the lidar system sends so many laser points through even the densest vegetation to the earth’s surface, researchers can later extrapolate the entire vegetation on a computer, providing an amazingly detailed representation of the topography in the scanned area.

Lidar makes structures visible
When Prümers and his team flew over the area surrounding six known Casarabe sites in 2019, the lidar technology made a total of 26 settlements visible, 11 of which had not even been discovered yet.

“When you walk along there, of course you notice the elevation changes, you really have to climb up these pyramids because their slopes are steep. But even when you’re standing at the top of the pyramid, which is over 20 meters high, you can’t really see very far from there because of the dense vegetation,” says Prümers, describing the arduous work in the rainforest.

“You will never really be able to get an impression of the site in its entirety or even in partial areas. In this respect, these lidar images are of course the optimal tool for us! Also to be able to show other people what was there, what we suspected and what we now know,” Prümers explains. “Now we have these incredibly informative lidar images and all of a sudden everything is obvious.”

Structures speak to a complex society
Thanks to lidar technology, the large settlement structures, each more than 100 hectares in extent, are visible. Lidar also reveals causeways and an elaborate irrigation system of canals and reservoirs.

Presumably, the widely ramified causeways connected the settlements even during floods during the rainy season, and the sophisticated irrigation system presumably allowed for sustained agriculture even during dry periods.

Lidas Scan der Sieglungen in Bolivien
In the center of one of the settlements stood an earth pyramid about 22 meters high.

But whether this water infrastructure served the drinking water supply or an irrigation in the extremely dry weeks in August or whether fish or turtles were bred there, must be further investigated. It is also unclear what function the monumental pyramid had.

No stone far and wide
To make matters worse, the archaeologists will not come across any stone buildings at the sites, because in the “alluvial soil there is only clay and sand, but not a single stone far and wide,” Prümers explains. The platforms of the representative buildings were all made of earth, and on top of them were wooden structures, of which only postholes have survived.

“In our excavations we found a few stones, but they were all imported. They were ornamental objects, sometimes an axe, but nothing that somehow originated in the region. In that sense, you won’t find architecture in our sense, no brick buildings, no stone buildings, but you will find impressive buildings made of earth and now and then traces of the ephemeral wooden architecture.”

Accordingly, the state of knowledge about the Casarabe culture is still very rudimentary, admits archaeologist Prümers. On the basis of the more than 100 graves found, however, we can already say something about their eating habits, for example, that they ate corn and what they hunted.

What led to the decline of the Casarabe culture?
Why the settlements were abandoned after about 900 years of use and the Casarabe culture disappeared around 1400 AD, i.e. before the arrival of the Spanish conquerors, is still unclear. Archaeologist Prümers “can very well imagine that climatic changes may have been the decisive factor. The problem is that it will be difficult to prove”.

Whatever caused the decline of the Casarabe culture, the size and complexity of the settlements now documented speak for urban centers with very complex social organizational structures already in pre-Hispanic times. The history of the Amazon basin must therefore be rewritten.

German dw.com was used as a source.

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