- New study reveals 24 previously unrecorded pre-Columbian archaeological sites in the Amazon, known as earthworks, and estimates there may be more than 10,000 such sites still hidden in the forest.
- Ancient earthen structures provide evidence of occupation by pre-Columbian societies in the Amazon over centuries and even millennia.
- According to experts, these remains can help people and communities prove their ancestral presence in the territory and press for the demarcation of new Indigenous Lands.
The Amazon is considered home to indigenous people who, thousands of years ago, worked the land in ways we are familiar with today. They built ditches, ponds, wells, and other structures that show that the rainforest was not “pristine,” as was often mistakenly believed. Centuries later, the development of these populations was violently interrupted with the arrival of the first European ships in the Americas.
The true extent of Amazonian settlements and the transformation of the landscape by these indigenous populations, however, remains uncertain, despite the efforts of researchers.
Now, research recently published in the journal Science reveals an unprecedented estimate of the number of pre-Columbian “earthworks” archaeological sites still hidden in the Amazon rainforest, based on both already-known and new structures that have been discovered and reported in the Amazon. study.
Researchers discovered more than 20 earthen constructions under the Amazon rainforest canopy in total, which include a fortified village, defensive and ceremonial sites, crowned mountains, megalithic monuments, and riverine floodplain sites. All this thanks to an advanced remote sensing technology known as LiDAR, which means “Light Detection and Ranging” in English.
Capable of collecting information about the structure of the forest and the terrain below the forest, the aerial sensor has revolutionized the way information is obtained about the Earth's surface, allowing archaeological discoveries in densely forested areas.
The authors of the article estimate that there may be more than 10,000 earthworks still hidden in the forest, and have also identified more than 50 species of domesticated trees that indicate the likely occurrence of archaeological sites of this type, which suggests active indigenous forest management practices. by pre-Columbian societies.
“Our findings clearly suggest that the Amazon had sizable human populations, perhaps totaling 8 to 10 million people. This number is higher than previous estimates, which have been debated for decades by anthropologists,” says William Laurance, a tropical ecologist at Australia’s James Cook University in Cairns, and co-author of the study.
Charles R. Clement, a recently retired senior researcher at the National Institute for Amazonian Research in Brazil who was not involved in the study but collaborated with many of its authors, told in an email that, as he sees it, this is a clear indication that there would be many people throughout the Amazon, especially in the southern region — “probably millions,” he says.
For researchers, the findings contribute to the current debate about whether the Amazon Basin was home to the historical presence of large indigenous populations.
24 new archaeological sites
The study involved an intercontinental team of more than 200 researchers from 24 countries, who identified 24 previously unreported pre-Columbian archaeological sites in the southern, southwestern, central and northern regions of the Amazon, after scanning LiDAR data from areas totaling 5,300 square kilometers , which is equivalent to less than 0.1% of the Amazon.
These 24 sites reveal a variety of structures that indicate people were using different parts of the Amazon in different ways.
In the southern region, six earthworks that could be part of a fortified village of an ancient town square were discovered in the Alto Xingu Basin, in Mato Grosso.
“These villages had peripheral ditches, roads with curbs, raised sidewalks, artificial lagoons, dikes, fish ponds and other earthen structures”, which reveals the existence of “regional and organized policies between peers and an intermediate social form between autonomous villages within the Alto
In the southwest of the Amazon, ten earth structures were found that could be defensive and ceremonial sites, known as “geoglyphs”, says the researcher, in the municipalities of Senador Guiomard and Rio Branco, in Acre. Peripato explains that the presence of funerary urns in these types of sites and the absence of anthropogenic soils and ceramics “are evidence that the use of these structures was limited to religious and community gatherings.”
In the Guiana Shield region, six sites were discovered in the municipalities of Laranjal do Jari, Ferreira Gomes and Oiapoque, in Amapá. The earthen constructions found in the crowned mountains, called “permanent settlements” in the study, were used for both “ceremonial and domestic functions”, explains the researcher, while the megalithic structures served only as “ceremonial sites”.
In the Central Amazon, two earthen structures were found in the municipalities of Boa Vista do Ramos and Óbidos, in Amazonas and Pará, respectively. It is believed that these, in these regions, served as riverside sites in floodplains, “which were used to collect aquatic food during the rise and fall of river levels in the Amazon”, explains Peripato.
Laurance says the study and related work suggests that indigenous groups in the Amazon had sophisticated means of rotational/shifting agriculture, irrigation, village development and defensive fortifications to help repel external attacks.
“This is causing researchers to reevaluate their thinking about the technical skills of the native Amazonian peoples, which were more advanced than many thought,” says the co-author.
The fight for recognition of indigenous territories
The research “demonstrates that the Amazon has always been the home of indigenous peoples”, says Toya Manchineri, general coordinator of the Coordination of Indigenous Organizations of the Brazilian Amazon (Coiab), which defends the rights of indigenous peoples to land, health, education , culture and sustainability, in a telephone.
He emphasizes that the data is very important, especially at a time when indigenous peoples in Brazil are “fighting a battle over the issue of the time frame”, a controversial thesis that would restrict the legal recognition of indigenous territories throughout the country.
The time frame advocates the invalidation of all claims to indigenous lands that were not physically occupied by indigenous communities on October 5, 1988, the day the Brazilian Constitution was promulgated. Although this doctrine was declared unconstitutional by the Federal Supreme Court in September, the Brazilian National Congress approved a bill ( PL 2903 ) with a similar objective, defying the court's decision. The PL was partially vetoed by President Luiz Inácio Lula da Silva, only to have the veto overturned by Congress in December.
Clement says the researchers point out that the earthworks and domesticated forests provide direct evidence of indigenous habitation over centuries and even millennia, which contributes “to helping indigenous people demonstrate that they have a right to these territories.”
He adds that this is very important today, “since the Ruralist Caucus in the Brazilian Congress wants to stop all demarcation of indigenous territories so that Brazilian agribusiness can expand without being disturbed”.
Manchineri explains that, with discoveries such as land works, science goes against the interests of sectors such as agribusiness or those involved in the invasion of indigenous territories. “It’s bad for them because it demonstrates, with scientific quality, that indigenous peoples have always lived in the Amazon and that the State’s own actions have been decimating several indigenous populations.”
He says the study data is also important for indigenous organizations and peoples in their efforts to demarcate new territories. Archaeology, he adds, through the discovery of these sites, has revealed “where, how and for how long indigenous peoples lived in the past”.
The coordinator explains that it is not as if indigenous peoples now want to retake cities, but rather that the Brazilian State at least recognizes the harm that has been done to these indigenous populations: “Help those who still live in the best possible way, so that they can increasingly strengthen themselves as indigenous peoples and strengthen their ancestral knowledge”.
Manchineri also warns: “Otherwise, given the current level of invasion, we will be at the mercy of a lot.”
Thousands of earthworks may still be hidden
The study's authors say their findings could serve as the basis for uncovering much more extensive evidence of indigenous habitation, as they estimate that between 10,272 and 23,648 earthworks may still be hidden beneath the Amazon Rainforest. The estimate was obtained by combining the 24 newly detected structures with the more than 900 previously recorded earthworks and advanced statistical modeling.
The number suggests that previously documented land structures in the Amazon represent less than 10% of the total, with more than 90% remaining undiscovered, according to the research.
The scientists also showed the remarkable correlation that “domesticated [tree] species are related to the likelihood of construction in the area,” explained Hans ter Steege, researcher at the Naturalis Biodiversity Center and professor at Utrecht University in the Netherlands, co-author of the article,
This connection was established by comparing the likely locations of earthworks with historical records of domesticated tree species in the Amazon. Of the nearly 80 such species, 53, including cocoa ( Theobroma cacao ), cupuaçu ( Theobroma grandiflorum ), peach palm ( Bactris gasipaes ), Brazil nut ( Bertholletia excelsa ) and others, many of which are still being used, coincided with probable earthworks sites, says ter Steege.
In this regard, Clement notes that unlike the Middle East, “where Euro-American society and agriculture originated,” the Amazon was inhabited by people involved in arboriculture, “the culture of trees, forests, and gardens.” . The researcher mentions that “there was no agriculture before the European conquest. However, the Amazon ecosystems, especially the forests, fed millions of people. What can society learn from this?”
Manchineri says he believes that these results strengthen the view that indigenous peoples have a lot to contribute to the country's development. “It’s a shame that government officials don’t look at it that way.”
He suggests that perhaps the current large-scale agricultural system could look at indigenous knowledge from a different perspective, “and try to adapt to work without despoiling the environment.”
A non-uniform distribution
Ancient earth structures with social, ceremonial and defensive functions, such as circular ditches, geoglyphs, lagoons and wells built using earthmoving techniques, are some of the types of pre-Columbian formations found in the Amazon and provide evidence of indigenous occupation in the basin by societies that they built with earth .
The study suggests that pre-Columbian societies carried out these constructions in all regions of the Amazon, “covering a wider area than previously thought”, although these locations were not evenly distributed, as the earthworks are probably more concentrated. in certain regions, especially in the southwest of the Amazon.
“We predict that 90% of the Amazon forest has a very low chance of having work on the land, so this type of modification to the Amazon forests may have occurred mainly in 10% of its area,” said ter Steege in a press release.
The study's lead author explains that the occurrence of these structures is more common in transitions from tropical forest to savannah, in places that combined environmental conditions that “probably facilitated construction with earth, offering periods with less precipitation and higher temperatures and soils with better texture.”
Laurance adds that indigenous groups “were evidently much less common, perhaps even absent, in areas of deep rainforest, wetter areas where fire-based agriculture is difficult, and in the large expanses of the basin that have nutrient-deprived soils.” .
He goes on to say that the study reinforces previous perspectives that argue that indigenous populations in the Amazon were “largely confined to drier or marginal areas, where fire-based agriculture was much easier than in wetter areas.”
A “domesticated” biome
Clement says the newly revealed discoveries go against people's belief that the Amazon was "the last frontier, almost untouched by human hands until European conquest, modern deforestation and fire."
He opposes the idea that human cultures would have been limited and determined by the environment. Instead, the researcher, as well as others, supports the assumption that human cultures would have modified the environment as desired, just as they do today. “The Amazon was not pristine as most people imagine, but was completely domesticated by indigenous people, who were exterminated by European slavery, disease and war.”
Peripato explains that the suggestion that at least 10% of the Amazon may have been modified by pre-Columbian societies “is based on this unique and specific type of pre-Columbian formation”, that is, earthworks. However, says Clement, “not all societies moved earth in large quantities.” This means that there are other types of archaeological evidence in the Amazon that indicate different forms of occupation and transformation of the landscape by indigenous peoples.
“If we consider all types of pre-Columbian records, such as anthropogenic soil and ceramics, the extent of the modification made by these societies throughout the Amazon can be demonstrably greater,” says Peripato.
The soil he refers to, also known as terra pretas of the Amazon , is a nutrient-enriched anthropogenic soil widely accepted as an indication of long-term settlement by pre-Columbian societies, which have been found especially at sites in the Central and Eastern Amazon .
Clement says there are also domesticated forests themselves , which are likely contained in areas similar to those where pre-Columbian earthworks occur, but in other locations as well.
He adds that all this archaeological evidence can be found in varying sizes along large and small rivers and, as there were also some indigenous peoples who did not usually settle, there may be more dispersed and “even smaller and more ephemeral” sites.
The researcher reports that wherever archaeologists search, they find new sites, “sometimes with earthworks, often without”, and states that the entire Amazon was domesticated, “but this does not mean that every tree or palm has been planted. There are many ways to create a tamed forest.”
Clement continues: “Some indigenous people built earthworks, others did not. Some practiced agriculture, others did not. Everyone managed their forests to increase food availability.”
There is controversy about this in the scientific community, and there are those who criticize this interpretation of a domesticated Amazon, arguing that “dense, settled populations” would have been found “in areas rich in resources, such as along the main channel of the Amazon River”.
In any case, the notion of an Amazon historically intact and free of people influences modern struggles. Clement says that this image helps with dreams of conserving forests without their people, whether indigenous or traditional, in addition to fueling development projects. “Brazil’s powerful agribusiness says that empty forests must be replaced by grain fields, for example, industrial monocultures of soy, corn, cotton and pastures, to feed the world.”
Innovative research
Peripato explains that this study contributes to knowledge in three main areas, one of which is “archaeology itself through innovative discoveries and the highlighting of several areas for archaeological prospecting”.
He says that, in the field of environmental sciences, progress is in demonstrating the level of human interference in the region, “which may have implications for its current functioning and the way we shape its future”.
In applied computing, the researcher highlights a leap in the ability to analyze thousands of points within the data collected by the LiDAR sensor, which “operates using laser pulses to measure distances and create detailed representations of the terrain, objects and structures in our environment”.
The statistical modeling that allowed us to estimate the number of pre-Columbian earthworks still hidden in the forest is another progress in this field. “We used the 24 new discoveries, together with the structures previously cataloged up to that point, and developed a probability model for the entire Amazon”, explains the study's lead author.
Laurance says the research helps resolve the long-standing debate over the number of native peoples who occupied the Amazon, “clearly favoring higher numbers.” According to him, this is innovative research. “This type of work, on such a large scale, has never been done before.”