Mystery of Amazonian Circles

A range of earthworks scattered throughout the Bolivian and Brazilian Amazon, comprising square, straight and circular ditches, are being studied by archaeologists and environmentalists. Since the 1980s, deforestation has revealed massive earthworks in the form of ditches up to 16 feet (5 meters) deep, and often just as wide. Satellite images of the upper Amazon Basin taken since 1999 have revealed more than 200 geometric earthworks spanning a distance greater than 155 miles (250 kilometers). They may have been used for defense, drainage, or perhaps ceremonial or religious reasons. They were substantial features, with ditches up to 10ft (3m) deep and 13ft (4m) wide. The researchers took core samples of the sediments from them and have discovered that they were created 2,000-3,000 years ago, before there was rainforest in the Amazon Basin, when the environment was, in fact, savannah. 

 

These mysterious Amazonian Circles appear to predate the rainforest

The discovery that the human activity came before the forest answers some questions, like how Amazonian people could have built in the rainforest with no more than stone tools (they didn't have to), how many people would have been necessary to construct the structures (fewer than if clear-cutting had been required), and how the population survived (by growing maize). But who built the structures and what functions they served remains a mystery.


Sources:
Fortean Times Magazine Vol.318 September 2014: "Mystery Amazonian Circles"

http://news.nationalgeographic.com/news/2010/01/100104-amazon-lost-civilization-circles/

http://www.huffingtonpost.com/2014/07/08/rainforest-rings-amazon_n_5567031.html

Pic Source:
Fortean Times Magazine: "Mystery Amazonian Circles" page 16