Mysterious Earthen Rings Predate Amazon Rainforest

Mysterious Earthen Rings Predate Amazon Rainforest.

A series of square, straight and ringlike ditches scattered throughout the Bolivian and Brazilian Amazon were there before the rainforest existed, a new study finds.

These human-made structures remain a mystery: They may have been used for defense, drainage, or perhaps ceremonial or religious reasons. But the new research addresses another burning question: whether and how much prehistoric people altered thelandscape in the Amazon before the arrival of Europeans.

“People have been affecting the global climate system through land use for not just the past 200 to 300 years, but for thousands of years,” said study author John Francis Carson, a postdoctoral researcher at the University of Reading in the United Kingdom. [See Images of the Ancient Amazonian Earthworks]”

Ancient landscape

An examination of the two cores — one from the large lake, Laguna Oricore, and one from the smaller lake, Laguna Granja — revealed a surprise: The very oldest sediments didn’t come from a rainforest ecosystem at all. In fact, the Bolivian Amazon before about 2,000 to 3,000 years ago looked more like the savannas of Africa than today’s jungle environment.

The question had been whether the early Amazon was highly deforested or barely touched, Carson said.

“The surprising thing we found was that it was neither,” he told Live Science. “It was this third scenario where, when people first arrived on the landscape, the climate was drier.”

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