Under the trees of the Amazon jungle are hidden the archaeological remains of what was once a large village built by pre-Columbian indigenous communities before the arrival of Europeans to America. The ancient city had causeways, artificial ponds, dikes, ditches, cemeteries, roads with platforms, fish dams, and was located in what we now know as the Xingu River basin, south of the Brazilian Amazon. These ruins, which remain hidden by the dense vegetation of the forest, were discovered by a group of scientists thanks to a special remote sensing system called LiDAR, which uses laser beams to map small changes in the topography of the jungle floor and allows reconstruction. in three dimensions what is on the surface.
Vinicius Peripato and Luiz Aragão, from the National Institute of Space Research of Brazil, led a work of more than five years in which they flew over 5,315 square kilometers in a region of the Amazon with drones and planes equipped with the LiDAR system. Only in that small area of land, which represents 0.08% of the seven million hectares of the largest tropical forest in the world, they found 24 new archaeological sites similar to the ancient village. They decided, then, to combine their findings with a predictive spatial distribution model that allowed them to establish an estimate of the earth movements produced by communities throughout the jungle more than 500 years ago. The results of the study, published this Thursday on the cover of the magazine Science reveal that between 10,272 and 23,648 large-scale pre-Columbian archaeological structures in the Amazon remain to be discovered.
The origin of the work was a question impossible to answer without current technology: where and how many pre-Columbian sites are hidden under the canopy of the Amazon forest? Until the moment of the investigation, scientists from the nine countries that make up the jungle (Brazil, Peru, Colombia, Bolivia, Venezuela, Ecuador, Guyana, Suriname and French Guiana) They had discovered nearly 950 archaeological sites using the high-resolution satellite data provided by Google Earth. The problem was that only the earthworks that were in deforested areas could be seen. What is under the trees remained hidden. The LiDAR system, which stands for “Light Detection and Ranging,” changed everything.
In an interview with EL PAÍS, Peripato explains that this aerial sensor is an advanced remote sensing technology that “has revolutionized the way we obtain information about the Earth’s surface and its three-dimensional characteristics.” You no longer have to cut down the forest to know what is inside it. In recent years, LíDAR has also been used to discover the complex urban and rural network that the Mayans had throughout Mesoamerica: “Mesoamerican archaeological sites present very different characteristics from those of the Amazon due to the variety in construction materials: The Mayans used stone and the indigenous people of the Amazon used earth. LíDAR technology has substantially improved our spatial understanding of archeology in sites with forested landscapes,” the scientific article reads.
Peripato says that among the 24 archaeological sites they found defense and ceremonial sites in the southwest of the Amazon, known as geoglyphs. “The presence of funerary urns within this type 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,” says the researcher. They also found mountains conquered by indigenous communities in the Guiana Shield that were used for ceremonial and domestic functions, and riparian sites on plains of central Amazonia that were used to harvest fish during the rise and fall of river levels.
Carolina Levis, co-author of the work and professor at the Federal University of Santa Catarina, explains in a press release that this research helps disprove the widespread idea that the Amazon is a vast virgin forest. “The work shows us that there are many areas of the jungle that have already been the subject of extensive engineering, cultivation and plant domestication by pre-Columbian societies,” says Levis. And he adds: “these archaeological sites are proof that indigenous communities mastered sophisticated land and plant management techniques, which, in some cases, are still present in current knowledge and practices that can inspire new ways of living with the forest without need for its destruction.”
The research, furthermore, is an important step to think of the Amazon rainforest not only as a space of animal and plant biodiversity, but as a great source of archaeological research. Before we were certain that 427 species of mammals, 1,300 species of birds, 378 species of reptiles and more than 400 species of amphibians live in the Amazon River basin. Now we know that on the surface covered by the forest there are more than 10,000 large-scale earthworks that may hold the keys to better understand the customs and culture of the indigenous communities that inhabited the jungle for thousands of years.
Luiz Aragão tells EL PAÍS that the map also allows us to demonstrate that in regions with a high probability of finding archaeological sites there is an increase in the density of domesticated tree species. “This was an interesting result because it shows that pre-Columbian populations had a very close relationship with species that provided them well-being, especially food and fiber. From there we can conclude that they manipulated the ecosystem to increase the density of these species.” In fact, research shows that the number of edible fruit and nut plants and trees increased significantly in places where archaeological sites are believed to be located. The authors identified relationships between the predicted probability of earthworks and the occurrence and abundance of domesticated tree species and found a significant association between the two. “This suggests that active pre-Columbian indigenous forest management practices have long shaped the ecology of modern forests throughout the Amazon,” the article says.
Despite the novelty of the research, Aragão is cautious in pointing out its limitations. When asked if it is possible to conclude that there are more than 10,000 unexplored pre-Columbian archaeological sites in the Amazon, he answers forcefully yes, but it is clear that it is an estimate. “Based on the existing number of known structures and our prediction model, we expect that many sites are still hidden beneath the canopy. Of course, this is an estimate based on statistical methods and has uncertainties. But it is very likely that there are thousands of archaeological sites that are there to be discovered,” he explains to EL PAÍS.
Hans ter Steege, co-author of the work and researcher at the Naturalis Biodiversity Center and the University of Utrecht, states that these archaeological sites must be concentrated in specific areas of the jungle: “We predict that 90% of the Amazon forest has very few possibilities of having earth movements, so this type of modification may have occurred mainly in 10% of its area,” says the scientist in a statement.
Although the size and characteristics of the thousands of archaeological sites in the jungle are still not well known, this work opens new avenues of research so that future scientists have a compass to know where to explore. “Amazonian forests deserve protection not only for their ecological and environmental value but also for their high archaeological, social and biocultural value, which can teach modern society how to sustainably manage their natural resources,” the research concludes.