Humans have been living in the Amazon rainforest for at least 4,000 years. In a surprising discovery, scientists have found more than 450 earthworks in the western Brazilian Amazon rainforest. Researchers led by Jennifer Watling of the University of Sao Palo investigated an area of about 8,000 square miles in the Brazilian state of Acre. Findings of the study were published in the journal Proceedings of the National Academy of Sciences.
The geoglyphs had a ritual significance
The Stonehenge-like earthworks were built about 2,000 years ago by the indigenous people of Brazil, long before the Europeans arrived. For centuries, the geometric enclosures were hidden by dense forests. But modern deforestation and satellite technology eventually helped reveal their presence. The geoglyphs measure 36 feet in width, 13 feet in depth, and 300 to 1,000 feet in diameter.
Excavations show a highly formalized architecture made of squares and circles. Since few artifacts were found at these sites, scientists believe that the geoglyphs were used to carry out ceremonial or ritual activities about 2,000 years ago. The absence of cultural materials indicates that the earthworks were kept “clean” for ritual purposes. Their forms and sizes suggest that they were neither defensive structures nor permanent villages.
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Has Amazon rainforest always been a pristine wilderness?
Watling and her colleagues dug soil samples from holes five feet deep within and outside two of the earthworks. They used charcoal from artifacts found at the bottom of some of the geoglyphs to date the sites. They concluded that the sites were built between first and 15th centuries. Charcoal layers, which indicate the fire, suggest that humans moved into the region about 4,000 years ago.
The discovery of Stonehenge-like earthworks is significant because it overturns the notion that the Amazon rainforest has always been a pristine wilderness. Researchers found that bamboo has been dominating the Amazonian ecosystem for more than 6,000 years. More importantly, the indigenous people in Brazil built these sites without major deforestation or alternation.
The geoglyphs were abandoned about 650 years ago
Instead of burning or cutting trees on a grand scale, they would make only small clearings for the earthworks. The ancient indigenous people encouraged the growth of beneficial plants such as palms that provided them food and building materials. Palms became less common in the region after they abandoned the geoglyphs some 650 years ago. The large-scale, long-term deforestation of the Amazonian rainforest is only a modern phenomenon.
Geoglyphs are large structures made on the ground. They are mostly formed using trees, rocks, gravel, or other durable elements. Watling said these geoglyphs were similar to Stonehenge, which was built about 2,500 years ago.