The Lost Civilizations of the Amazon: Did Millions of People Once Live in the Amazon Rainforest?

LiDAR reveals five times more earthworks than satellite imagery and a civilization of millions

In 1925, British Lt. Colonel Percy Harrison Fawcett and two companions entered the Amazonian jungle and disappeared. I came across Fawcett’s story when I was very small, and it fascinated me. I devoured every book, documentary, and snippet of information I could find on Fawcett and recent research into Amazonian civilizations. 

As it turns out, years before their disappearance, Fawcett had come across a document known as Manuscript 512, written by a Portuguese frontiersman, João da Silva Guimarães, describing the ruins of an ancient city in the Brazilian jungle. The veracity of this document is questionable, but Fawcett had come to believe that the Amazons had once contained vast civilizations and that the ruins of these people could still be found hidden in the jungle. A belief that would lead him, his son, and his son’s friend deep into the Amazon, where they disappeared without a trace.

For decades, it was believed that the dense, infertile soil of the Amazon jungle made it nearly impossible for large-scale civilizations to take root there. But as the decades progressed and new technologies emerged, including satellite, aerial, and LiDAR imagery, earthworks began being discovered.

While it is now well known that some form of ancient, large-scale civilization once existed in the Amazon, its exact scale remains a matter of debate, and many structures have been detected only on deforested land, leaving much of the dense jungle unexplored.

In a recent study, Martti Pärssinen and his colleagues conducted a LiDAR survey of over 4,430 km of flight range, documenting previously unknown earthworks. Using this data, they estimate the population size of an ancient Amazonian culture known as the Aquiry into the millions.

Hidden in the Rain Forest

Over the past few decades, hundreds of earthworks (geoglyphs) have been discovered, with many concentrated in Brazilian Acre and neighboring states. Their discovery overturned the long-held assumption that dense human settlement was limited to the Amazonian floodplains, showing instead that large populations also existed in the forested areas.

This has led researchers to estimate that the pre-colonial Amazonian population likely numbered between 1.5 and 2 million, with upper estimates suggesting 5 to 10 million. However, many prior discussions were shaped by LiDAR surveys conducted in Bolivia and Ecuador; these surveys did not cover large enough areas to support such population estimates.

To better understand the extent of earthworks and associated population density, the authors combined prior satellite and aerial data with a more recent LiDAR survey. These previous surveys had identified nearly 1,300 earthworks across 134,000 km² of land in southwest Amazonia, with the vast majority dating to the Aquiry civilization starting over 2,500 years ago, known for their geometric ditched enclosures.

One of the problems with these earlier surveys was that they were dependent on various factors, including vegetation density, season, and sometimes year. I would know, in university we had to do a satellite survey of parts of South Africa to find, identify, and document kraals (circular structures used to keep cattle). 

We quickly learned that these kraals were not always visible in the landscape. For example, in one area, the kraals I documented only showed up on satellite images taken in winter, but not in summer due to vegetation growth. In other instances, they were visible in images taken in one year but not the following or previous year. The Amazon has an additional problem: the dense forest canopy makes it almost impossible to see any of these structural remains unless that area of land has been cleared.

That’s where LiDAR comes in, for it can (usually) penetrate even dense jungle canopies.

Finding an Ancient Civilization

In 2024, researchers conducted 4,430 km of LiDAR surveys over 4,497 km² in Acre and Amazonas. This revealed 432 earthworks, including 396 previously unknown structures. This LiDAR survey revealed five times as many earthworks as satellite imagery had previously detected. This included areas where satellite imagery had revealed 30, while LiDAR in the same area revealed 156.

Just in case, let me explain how LiDAR works and why it can ‘see’ things satellite and aerial imagery cannot. LiDAR is a remote-sensing technology that functions by shooting pulses of infrared at a landscape and measuring how long it takes for that light to bounce back. This allows it to calculate distances, which in turn are used to create detailed 3D maps of the ground below. As ditches and groundworks differ in height from their surroundings (deep ditches and high groundworks), the map records them at different distances from the surrounding ground and canopy.

So even if you cannot see them from a plane, some of that infrared penetrates through the canopy, hits the earthwork, and bounces back. 

The study found that these earthworks belonged to the Aquiry and had been built between 600 BC and 850 AD. Most were between 0.35 and 14 ha in size (2.4 to 34.6 acres), though the largest was ~50 ha (123.6 acres).

One reason satellite imagery had failed to detect some of these works was that many were ditch-less, making them much harder to spot with traditional satellite imagery. While many previously documented geoglyphs were found to consist not of a single but of multiple embanked structures, which are typically invisible in aerial imagery.

The researchers then applied the data they had for low and high-density population zones across Amazonia. They determined that the area likely contained between roughly 23,760 and 29,500 earthworks, around 20 times more than any previous estimate for the Amazonian southern rim.

Their data also allowed them to estimate the extent of the Aquiry population’s civilization. No earthworks were found in the upland interfluve areas surveyed (possibly reflecting unoccupied buffer zones or simply dense forest obscuring the terrain model), and, excluding any geoglyphs built after the 9th century AD (likely built by another civilization), they found that the civilization occupied a cultural area of about 183,000 km².

Might and Purpose

Of course, such sites were not all occupied at the same time, which factored into population estimates, and each had different functions. Based on current knowledge, the researchers proposed that these earthworks functioned as public, ceremonial, and political gathering centers, as they do not show evidence of permanent occupation or defenses. This form of precolonial urbanism they compare to the Inca State’s practice of hosting temporary gatherings of diverse groups.

Despite not being permanently occupied, at least not by masses of people, they would have required substantial manpower to build, division of labor, and understanding of mathematics and geometry. On top of initial construction, maintenance of these sites and continued construction for over 1,500 years would have likely been linked to administrative, sociocultural, and cosmological motivations.

In 2009, the existence of roughly 200 earthworks, each estimated to have required at least 300 people, led to a population estimate of around 60,000. Considering the current study estimates between 24,000–30,000 total earthworks, of which 2/3rds belong to the Aquiry period, that estimate has been radically revised.

Using Bayesian and Kernel density modeling, the researchers determined that 25–60% of Aquiry earthworks were likely in simultaneous use around 100–300 AD (the civilization’s apparent peak). That’s around 4,165–10,000 in use at the same time.

Given that one earthwork required around 300 people to build and maintain, this puts the total population estimate at the height of the Aquiry period between 1.25 and 3 million people, blowing previous estimates out of the water. And this is likely an underestimation.

Why? Well, just as satellite imagery missed a few earthworks, it is possible LiDAR also missed some, especially in particularly dense forest areas. In fact, across various survey areas, or blocks, between 11 and 36% of the area was so dense that even LiDAR could not penetrate, suggesting there may well be hundreds more undocumented earthworks. With these emerging earthworks, population estimates range from 1.6 to 3.8 million.

This is all well and good, but wasn’t one of the main reasons people thought dense populations could not exist in the Amazon that the soil was simply infertile? I mean, sure, people could cut down some trees to make way for their earthworks, but if they cannot sustain the population living there, there is no point in building the earthwork in the first place.

Well, recent studies have shown that the soil, especially in the Aquiry region, is unusually nutrient-rich for the Amazon, making it well-suited for agriculture. Further evidence of this includes the discovery of various domestic and semi-domestic plants in earthworks, including palm trees and Brazil nuts, as well as plant remains such as squash, maize, sweet potato, chili peppers, beans, and peanuts, all requiring cultivation. This suggests that the Aquiry people actively managed and cultivated their landscape.

So, it seems the Amazon was not always a sparsely populated area; ancient civilizations not only lived there but also thrived. As technology advances, new research is uncovering ever more evidence of these civilizations. With initial satellite images finding the first few earthworks and lidar now penetrating deep into canopies, many more previously missed earthworks have been uncovered. While research on soils and plant remains has shown areas of the Amazon are far more fertile than previously assumed, and were once used for the cultivation of a myriad of crops, which would have supported not just thousands but millions of people.

If only Fawcett had known he was right (kind of) after all. I wonder just how many ancient earthworks and civilizations are hidden beneath the dense jungle canopy.

What else do you think we may find in the jungles of the Amazon, and what happened to these civilizations?

Let me know your thoughts, and if you’d like to support the countless hours I pour into researching, writing, and bringing these hidden corners of history to life, why not Buy Me A Coffee

References

Pärssinen, M., Kalliola, R., Ranzi, A. et al. Over 20,000 precolonial earthworks in the Southwest Amazonia. Nature (2026). https://doi.org/10.1038/s41586-026-10835-7

Vaz, J. (2026, July). Odd shapes hidden in dense Amazon rainforest reveal sprawling ancient civilization. Science. https://www.science.org/content/article/odd-shapes-hidden-dense-amazon-rainforest-reveal-sprawling-ancient-civilization