Researchers found hundreds of monumental constructions, which can be seen from above, from airplanes, in a region that encompasses the south of the State of Amazonas and portions of Acre, in the Amazon.
The structures were built thousands of years ago, in a region that is far from large rivers and, according to scientists, may have housed millions of people.
"These people performed monumental geometry in the Amazon at the same time that Pythagoras developed his theorem in Greece", compares paleontologist Alceu Ranzi, president of the Amazon Geoglyphs Institute and one of the authors of a recent study on the topic.
Understand below what the new findings reveal about the past of the largest tropical forest in the world — and the details about the so-called Aquiry civilization, responsible for creating the geoglyphs, the name given to these enormous structures excavated in the earth.
Credit, Martti Pärssinen & Fabio de Novaes
A technology that allows you to uncover the past
The most recent revelations about geoglyphs and the Aquiry civilization were the subject of a scientific article published in July in the famous academic journal Nature.
The work was carried out by scientists from the Iberoamerican Institute of Finland, in Spain, the University of Helsinki, Finland, the University of Turku (also in Finland), the Federal University of Acre, the Federal University of Pará, among other institutions.
The researchers used a technology called LiDAR — an acronym for light detection and distance measurement.
Basically, this equipment uses a laser to measure distances and build complex maps in three dimensions.
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In regions like the Amazon, LiDAR can "see" what's under the trees — and analyze large areas without the need to deforest or visit all these places, one by one.
"This was the first ambitious LiDAR assessment in the Amazon", argues archaeologist and anthropologist Martti Pärssinen, from the University of Helsinki, Finland, and another author of the article.
Credit, Martti Pärssinen
Hundreds of monumental buildings
With the help of this equipment, scientists tracked an area of 4,400 km² between the states of Amazonas and Acre.
And, in this stretch, 432 earthen structures were identified — 396 of them never before recorded.
The geoglyphs associated with the Aquiry civilization were constructed between 600 BC and 850 AD.
Based on this data and satellite images, they estimate that the area occupied by the civilization reached around 183 thousand km² — less than 3% of the Greater Amazon, an area slightly larger than the territory of Uruguay.
The authors also calculate that, around the years 100 and 300 AD, this region was home to up to 3 million people — numbers that, according to scientists, are related to the monumentality of the geoglyphs.
“Most [of the geoglyphs] are ditches, and they vary in size,” explains Ranzi.
"There are ditches up to 15 meters wide and five meters deep", he adds.
The research authors suggest that building gigantic structures like these required a large community of people working together.
Credit, Rhuan Lopes
How were geoglyphs constructed?
"There is no stone in this region. Wooden material was possibly used, and baskets were used to carry [the earth]", replies Ranzi.
"It was a lot of labor, but we're not sure, because everything in the Amazon is organic, it disappears", details the researcher.
This means that it is impossible to find ancient "classic" signs of human occupation in this region, such as buried bodies, food remains or signs of camps and dwellings. Due to humidity, all this material decomposes over time, unlike what happens in drier regions of the planet.
In addition to the large number of labor and the need to divide tasks, experts believe that these constructions required knowledge of mathematics and geometry.
"We already had sufficient technological conditions in the Amazon for a gigantic civilization like Aquiry to build geoglyphs in the forest", reasons archaeologist and anthropologist Rhuan Carlos Lopes, from the Federal University of Pará, who also wrote the article.
Credit, Martti Pärssinen, Risto Kalliola & Fabio de Novaes
What were geoglyphs for?
One of the researchers' first hypotheses was that the geoglyphs would be strong, or defensive constructions, so that the population could protect itself against invasions and attacks.
But today, experts consider it more likely that they had ceremonial and political functions.
"If it is indeed confirmed that they are ceremonial structures, these people lived in peace because, to dedicate so much effort, so much work, it means that there were no enemies to worry about", speculates Ranzi.
Pärssinen raises another aspect that research in the region indicates: an absolute respect for nature.
"They never turned the rainforest into a savannah," he points out.
"Which means that the clearings and the felling of trees were large enough for subsistence, to grow corn, pumpkin, cassava, nothing else", adds the scientist.
In the article, the researchers argue that there was no permanent occupation of these structures: they were used to receive guests and hold ceremonies of a political, cultural, sporting or religious nature.
"Geoglyphs were used for meetings, to make political decisions and to organize religious ceremonies, and also for parties, dance and music", reinforces Pärssinen.
Field work, through excavations, indicates that these structures were very well cared for.
"There was maintenance of these spaces. It wasn't just building them, but maintaining them over the centuries, and this, obviously, also implies the existence of a set of knowledge", says Lopes.
Another important point: studies show that the buildings were connected by roads.
"We mapped 350 km of roads that connect the geoglyphs," says Ranzi.
According to him, the geoglyphs were not isolated structures, in the middle of the forest or landscape.
"These paths led to these locations, and these paths, as they approached the structures, increased in size."
"It's as if you were leaving the countryside onto a small street, which turns into a road and then becomes a two-lane, three- or four-lane highway", compares the scientist.
The end of the Aquiry civilization
During their investigations, researchers noticed something curious: geoglyphs stopped being built around 850 AD.
The reason for this is still not very well known.
Ranzi draws a parallel with what happened in the same period with the Mayans, who inhabited parts of Mexico and Central America.
"At that same time, the Mayans stopped building and using those palaces. The Yucatan pyramids were once again occupied by the forest," he notes.
"And something similar happened in the Amazon. The 800s were perhaps a period of some global environmental crisis," he suggests.
Ranzi has been researching Acre's geoglyphs for more than 40 years — he saw the first structures of this type during a flight, when he returned to Rio Branco after a trip.
At that time, most of these buildings could only be identified in areas that had been deforested and turned into plantations or pastures.
"For me, what caught my attention from the beginning was the monumentality of these structures. They are drawings measuring 400, 500 meters in diameter", he recalls.
Now, with the help of new technologies such as LiDAR, the work of archaeologists moves forward — with the advantage of knowing better where to excavate in search of more remains of the Aquiry civilization.
A new past for the Amazon
Research on geoglyphs is connected to a larger movement, which has been slowly unraveling the Amazon's past — and dispelling many myths about this place.
The first of them was that this was an untouched forest, with no signs of human occupation.
In recent decades, research in different fields of knowledge has demonstrated that this region was inhabited by millions of people long before the arrival of Europeans — and they left profound marks on the composition and structure of the largest tropical forest in the world.
"What we see in the Amazon is not a large natural forest, but rather a large, historically constructed garden", argues Lopes.
“And that, from my point of view, is very fascinating,” adds the researcher.
Estimates about the ancestral occupation of this territory are still growing: previously, studies calculated that the entire pre-colonial Amazon could support between 1 million and 2.5 million people, at most.
Later, this number rose to between 5 and 10 million people.
Now, with the suggestion that just a relatively small area of this forest could support up to 3 million individuals, it is possible that this number could increase again.
Another contribution of the study of geoglyphs is to understand how the so-called "firm land" was occupied.
Previously, it was believed that the Amazon occupation took place mainly on the banks of large rivers, where there were supposedly better conditions to obtain food.
But the geoglyphs are located precisely in the region between rivers, which is known as terra firma: recent research revealed that these places also had large populations, with the capacity to intervene in the forest and cultivate cassava, beans, pumpkin, corn...
"These people not only occupied the large rivers, there on the beaches, with an abundance of fish, ease of canoeing, and getting around. They also occupied the entire interior, at least in the south of Amazonas and Acre", reinforces Ranzi.
"They knew the topography, occupied places far from the rivers and traveled on foot along these paths."
“And this completely changes the view of how the occupation of the Amazon happened,” he concludes.
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