Lidar technology has helped reveal new evidence of settlements built by a “lost” pre-Hispanic civilization, resolving a long-standing scientific debate about the region’s ability to support a large population. Details of the study are published in the journal Nature.
Archaeological remains of low-density agrarian urbanism have been reported under the tropical forests of Southeast Asia, Sri Lanka and Central America. Until now, however, such evidence was lacking for the pre-Hispanic Amazon. It is now done. Indeed, researchers have recently discovered the presence of two remarkably large sites (147 ha and 315 ha) belonging to an ancient culture in the southwest of the Amazon.
The discovery was made using lidar technology. The idea is to release thousands of infrared laser pulses from a helicopter that bounce off the ground terrain every second. The technique thus makes it possible to reveal archaeological structures under dense vegetation that would otherwise have gone unnoticed.
The researchers thus discovered the remains of several settlements embedded in a network of roads, causeways, reservoirs and canals. Here lived the mysterious Casarabe people, who we know were present in the Llanos de Mojos region of the Amazon basin between 500 and 1400 AD.
A civilization more interconnected than previously thought
Until now, based on the accounts of the Spanish missionaries of the 16th century, it was accepted that the local communities were very isolated from each other. In reality, members of this people were much more numerous than previously thought, instituting a “low-density tropical urbanism over a wide area”, according to the authors.
These settlements could have housed thousands of people. Twenty-four are now known, nine of which were first discovered in the recent lidar study.
“Within an hour’s walk, you can reach another settlement,” explains Heiko Prümers, archaeologist at the German Archaeological Institute in Bonn.
The other takeaway is that these settlements were built around massive infrastructure of canals and reservoirs for water management. These waterways radiated in all directions from the main settlements. These systems may have been used to control seasonal flooding of the region or to allow corn and other crops to be grown in elevated areas. It is also possible that some reservoirs were used to raise fish.
This reliance on these facilities may also have cost them dearly. Researchers speculate that water scarcity during a prolonged dry period may have played a role in the disappearance of the Casarabe civilization around 1400 AD, more than a hundred years before the arrival of the Spaniards.