Hundreds of ancient earthworks built in the Amazon

February 6, 2017
Geoglyph photo. Credit: Jenny Watling

The Amazonian rainforest was transformed over two thousand years ago by ancient people who built hundreds of large, mysterious earthworks.

Findings by Brazilian and UK experts provide new evidence for how indigenous people lived in the Amazon before European people arrived in the region.

The ditched enclosures, in Acre state in the western Brazilian Amazon, were concealed for centuries by trees. Modern deforestation has allowed the discovery of more than 450 of these large geometrical geoglyphs.

The function of these mysterious sites is still little understood - they are unlikely to be villages, since archaeologists recover very few artefacts during excavation. The layout doesn't suggest they were built for defensive reasons. It is thought they were used only sporadically, perhaps as ritual gathering places.

The structures are ditched enclosures that occupy roughly 13,000 km2. Their discovery challenges assumptions that the rainforest ecosystem has been untouched by humans.

The research was carried out by Jennifer Watling, post-doctoral researcher at the Museum of Archaeology and Ethnography, University of São Paulo, when she was studying for a PhD at the University of Exeter.

Dr Watling said: "The fact that these sites lay hidden for centuries beneath mature rainforest really challenges the idea that Amazonian forests are 'pristine ecosystems`.

Geoglyph photo. Credit: Jenny Watling

"We immediately wanted to know whether the region was already forested when the geoglyphs were built, and to what extent people impacted the landscape to build these earthworks."

Using state-of-the-art methods, the team members were able to reconstruct 6000 years of vegetation and fire history around two geoglyph sites. They found that humans heavily altered bamboo forests for millennia and small, temporary clearings were made to build the geoglyphs.

Instead of burning large tracts of forest - either for geoglyph construction or agricultural practices - people transformed their environment by concentrating on economically valuable tree species such as palms, creating a kind of 'prehistoric supermarket' of useful forest products. The team found tantalizing evidence to suggest that the biodiversity of some of Acre's remaining forests may have a strong legacy of these ancient 'agroforestry' practices.

Dr. Watling said: "Despite the huge number and density of geoglyph sites in the region, we can be certain that Acre's forests were never cleared as extensively, or for as long, as they have been in recent years.

"Our evidence that Amazonian forests have been managed by indigenous peoples long before European Contact should not be cited as justification for the destructive, unsustainable land-use practiced today. It should instead serve to highlight the ingenuity of past subsistence regimes that did not lead to forest degradation, and the importance of indigenous knowledge for finding more sustainable land-use alternatives".

The full article will be released in the Proceedings of the National Academy of Sciences of the USA and involved researchers from the universities of Exeter, Reading and Swansea (UK), São Paulo, Belém and Acre (Brazil). The research was funded by the Arts and Humanities Research Council, National Geographic, and the Natural Environment Research Council Radiocarbon Facility.

To conduct the study, the team extracted soil samples from a series of pits dug within and outside of the geoglyphs. From these soils, they analysed 'phytoliths', a type of microscopic plant fossil made of silica, to reconstruct ancient vegetation; charcoal quantities, to assess the amount of ancient forest burning; and carbon stable isotopes, to indicate how 'open' the vegetation was in the past.

Explore further: Ancient human disturbances may skew understanding of Amazon and its impact (Update)

More information: Impact of pre-Columbian "geoglyph" builders on Amazonian forests, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1614359114

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9 comments

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Shootist
1 / 5 (6) Feb 06, 2017
Lesson for watermelons and other lost souls: There are NO pristine forests, rain or otherwise.
baudrunner
2.5 / 5 (2) Feb 06, 2017
In accordance with that paradox principle on which existence is founded, a rain forest is a collection of living and dying life, trees growing from dead trees, live animals and animal carcasses, beautiful rivers and man-eating fish. The most beautiful places, and, what I might be so bold as to suggest the closest that Earth comes to Eden, are to be found along the western coast of India. Countless idyllic oases featuring pools fed by falling water rimmed with drooping foliage - owned and inhabited by the King Cobra. Ya just can't win.

JongDan
5 / 5 (4) Feb 06, 2017
Their discovery challenges assumptions that the rainforest ecosystem has been untouched by humans.

Huh, I thought it's pretty established that the unique "terra preta" (black soil) of Amazonia, which is present in some places along rivers, results from fertilizing the ground with bone and charcoal specifically for farming purposes. It's pretty common and around 1500 years old.
TheGhostofOtto1923
1 / 5 (4) Feb 06, 2017
"Our evidence that Amazonian forests have been managed by indigenous peoples long before European Contact
Well thats the thing. They have no idea when eurasian/african contact first occurred. Euro conquerors destroyed records and obliterated cultures wherever they went.

And priestly emissaries who remained separate but instructed indigenes how to establish civilizations which were tailored for conquest, would have left minimal evidence by intent.
jeffreyjoemiller
4 / 5 (1) Feb 06, 2017
Some Native American cultures practiced forms of permaculture within forest environments. They would clear cut, remove the trees, in a circular space to allow for sunlight to reach the forest floor. In this circular plot of cleared land they would grow crops, in some cases building layered terraces within the circle to increase yield. In the outer rings they'd grow plants that repelled specific bugs, protecting the inner circle crops. After harvest, they would abandon the circle and let the forest grown back after just one growth cycle. In this way they never depleted any section of land and would enrich the forest soil. Perhaps some of the geoconstructions in the Amazon were for similar purposes.
cjones1
3 / 5 (2) Feb 07, 2017
There are many lost cultural structures being rediscovered using LIDAR and satellite imagery. Whether from catastrophes or war, little remains. I know that phosphorus blown from Sahara enriches the Amazon rainforests and time frames may exist from analyzing sediment cores, etc.
Sea levels were 400 feet (130 meters) lower over 10,000 years ago before the 1-3 mile high Pleistocene glaciers covering large areas of North America melted. There are probably lots of structures yet to be discovered under the seas that inundated former exposed land.
Pumastar
1 / 5 (1) Feb 08, 2017
Lesson for watermelons and other lost souls: There are NO pristine forests, rain or otherwise.

All thanks to big oil and their goony conglomorates
JongDan
5 / 5 (1) Feb 10, 2017
Euro conquerors destroyed records and obliterated cultures wherever they went.


Wrong. "Evil" Euro conquerors always made sure to document in details what satanic rituals local cultures practiced. The problem with Amazonia is that there are absolutely zero sources, so the collapse must have occurred earlier. Same with Mississippian culture.
TheGhostofOtto1923
1 / 5 (1) Feb 10, 2017
Wrong. "Evil" Euro conquerors always made sure to document in details what satanic rituals local cultures practiced
Since you cant source this, and since i know you made it up, what good are you? I mean, really?

"There were many codices in existence at the time of the Spanish conquest of Yucatán in the sixteenth century, but they were destroyed in bulk by the Conquistadors and Catholic priests soon after. In particular, all those in Yucatán were ordered to be destroyed by Bishop Diego de Landa in July of 1562."

"approximately 5000 Maya cult images were burned..."

-only 2 of 100s of examples.

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