May 28, 2022 - Science

Ancient cities' pyramids and causeways discovered deep in the Amazon

Screenshot from a 3D animation of the Cotoca site. The causeways extend from pyramids and other structures. Credit: H. Prümers/DAI

More than six centuries ago, people in the Casarabe culture built an extensive urban system deep in the Amazon rainforest that is detailed in a new study.

Why it matters: The enormous and complex settlement pattern hasn't been seen elsewhere in Amazonia, the archaeologists write, and indicates there may have been more urban areas in the region than researchers thought.

  • It is "the opening salvo of an Amazonian new orthodoxy," archaeologist Christopher Fisher of Colorado State University, who was not involved in the study, writes in an article accompanying it.

Details: The Casarabe lived in what is today Bolivia between 500 C.E. and 1400 C.E. Heiko Prümers of the German Archaeological Institute and a team of researchers studied 26 Casarabe sites, revealing 11 that were previously unknown.

  • Two large settlements — Cotoca and Landívar — feature monumental civic-ceremonial features, including platforms, mounds and pyramids, they report in the journal Nature.
  • Canals and reservoirs were used to move water around the settlements.
  • Raised causeways extend for several miles from the urban centers to smaller sites.
  • "The settlements are very closely interconnected by paths and canals, and they are never more than one hour's walk from the next settlement," Prümers says.

"The architectural layout of large settlement sites of the Casarabe culture indicates that the inhabitants of this region created a new social and public landscape through monumentality," he adds.

How it works: The team used light detection and ranging (lidar) technology attached to a helicopter to collect data from the sites.

  • Lidar emits a laser pulse and detects the amount of time it takes to return after it is reflected from an object or feature. That's used to determine the topography of the landscape, which reveals any features.
  • The technique has been used to study other ancient sites, including nearly 500 Mesoamerican sites across a large swath of southern Mexico.

The big picture: The pre-Hispanic history of Amazonia is largely unknown, Prümers says. "There are vast regions from which not a single archaeological site is known."

  • Those regions are also threatened by deforestation. When forests are cleared with bulldozers, Prümers warns, "not only does the forest disappear, but all archaeological remains near the surface are destroyed forever."

Go deeper: Archaeologists dig into digital data

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