The research further undermines the view that the Amazon was previously largely uninhabited. The dense vegetation of the rainforest would have simply made the construction of busy cities impossible, it has been said since the 1960s. Since then, scientists have increasingly questioned this, partly because of the discovery of ancient agriculture. This new research, which appeared on Wednesday in the scientific journal Nature, shows for the first time a network of cities in the Bolivian Amazon. The oldest cities, as large as some medieval European cities, date from the fifth century BC.
Twenty years ago, the German lead researcher, archaeologist Heiko Prümers, began surveying the hundreds of square kilometers of savanna. Searching for traces of an ancient civilization in the Amazon is challenging, because of any cities now little more than hills and ditches remain. Stones were not used at the time, earth and wood were the main building materials.
Nevertheless, Prümers and his team, in collaboration with the Bolivian government, came across indications of urban development. After three years of measuring, they mapped nearly an acre of land, revealing landscaped hills, canals and roads: a city predating Spanish colonization.
Researchers use light reflections to map ancient cities
Prümers, however, wanted to prove that the entire area he was looking at, about two hundred square kilometers, was structurally built up with towns and villages. He used a relatively new technology in archeology, called ‘lidar’. Just like a radar can visualize the environment with reflected sound waves, lidar does that with light (that’s what the ‘L’ stands for). The archaeologists flew in a helicopter over the Bolivian Amazon and shone special beams of light on the ground. Those rays of light bounced off the surface to be recaptured by the helicopter.
Using the time the light rays had traveled, the researchers measured how far away all structures on the ground and vegetation above were, providing a three-dimensional map of the savanna. They filtered out the vegetation from the three-dimensional map. After this ‘digital deforestation’, the contours of cities of the past became visible. Very valuable from an archaeological point of view, but also ecologically sound: ‘We felled trees with our calculators, not with axes’, says Prümers.
The largest city had a pyramid of 20 meters high
The structures that appeared were clearly man-made: in the largest city, a kilometer in length and width, stood a pyramid about 20 meters high. Around it, the researchers found U-shaped structures. Those resemble the structures in the Andes Mountains that are known to have had religious ceremonial functions. The whole was surrounded by three ring-shaped defensive ramparts, which show that the city has grown over the centuries, from about 500 to 1400. Finally, Prümers and his team came across roads, canals and large water basins.
The team visited these towns and villages on the ground. The researchers excavated at two locations and found ceramics and processed bone: ‘Everyday stuff that proves that these were really settlements,’ says Prümers.
‘Fascinating and convincing’, says Martin Berger, archaeologist at Leiden University. According to him, it ‘ends fifty years of discussion about the habitation of the Amazon’ and shows that there was indeed a complex culture. What exactly that culture looked like is still unknown. This requires further research. Berger: ‘I am already curious about what these excavations will show.’
It is still not known exactly how many people lived in Latin America before the arrival of the Europeans. That’s because the diseases the settlers brought with them often affected natives for them. As a result, little has been recorded about these peoples.