The lasers recorded 432 earthworks. The headline number is much larger: as many as 30,000.
Both figures belong to the same investigation, but they describe different things. One is an inventory within surveyed ground. The other estimates what may exist across a much wider region.
This episode follows that distinction through the evidence for circles, squares, ditches, embankments, roads, and the Indigenous communities that shaped southwestern Amazonia.
What the Survey Recorded
In 2024, researchers flew ten aerial laser-survey lines across parts of Acre and Amazonas in Brazil. Their 2026 study in Nature reports coverage of approximately 4,497 square kilometres.
The resulting inventory contains 432 earthworks. Thirty-six were already known, while 396 were newly documented by the researchers.
These are substantial additions to archaeological knowledge. They do not require the claim that tens of thousands of previously unknown structures appeared individually on the new maps.
Nor does newly recorded mean previously unknown to every person living in the region. Scientific documentation and community knowledge have different histories.
What LiDAR Sees
LiDAR measures reflected laser pulses. Some returns come from vegetation, while others reach the ground through gaps. Processing those measurements can produce a terrain model with vegetation largely removed from the visualization.
It does not turn the forest transparent or directly photograph a buried household. The model emphasizes differences in ground elevation, including banks, ditches, mounds, and road-like features.
A clear geometric outline can be strong evidence of deliberate earthmoving. Establishing its age, use, and relationship with neighbouring features requires further interpretation and often field investigation.
That is why the episode distinguishes what the terrain model reveals from the more detailed history researchers reconstruct around it.
How Hundreds Become Thousands
The regional estimate combines systematic survey strips with a pre-existing inventory derived partly from satellite imagery. The authors infer approximately 24,000–30,000 earthworks across their proposed cultural area.
The logic is sampling. Researchers use observed density and distribution to estimate the quantity beyond the scanned ground.
That estimate depends on how well the sample represents the wider landscape and how structures are recognized and classified. Deforested land and forested land may not reveal the same kinds of features equally well.
An estimated total is useful because complete coverage is difficult. Its usefulness does not make it equivalent to a count. More survey can test whether the inferred distribution holds.
What Does Aquiry Describe?
The paper uses Aquiry for a multicultural complex associated with shared monumental traditions. It should not be treated automatically as the inhabitants' own name or proof of a centralized empire.
The episode's archaeological landscape includes gathering places, managed vegetation, cultivated plants, and links between communities. It does not present an intact stone capital suddenly uncovered beneath the canopy.
Earth was a construction material capable of expressing planning, geometry, and collective labour. The absence of masonry does not make a landscape unbuilt.
At the same time, impressive architecture alone cannot tell us the precise political arrangements that organized its construction.
The Population Question Adds More Assumptions
The proposed 1.25–3 million inhabitants around AD 100–300 is a further step beyond estimating earthworks.
It depends on assumptions about how many structures were in use together and the size of the communities associated with building and maintaining them. A structure used intermittently for gatherings is not interchangeable with a residential village.
The published peer-review record shows substantial scrutiny of this reconstruction. Reviewers questioned the extrapolation, contemporaneity, household assumptions, and use of later settlements as comparisons; the authors defended their approach and revised the manuscript.
That exchange is part of evaluating the result. A published proposal can remain more uncertain than the mapped features on which it partly rests.
Counting enough labour to build a monument also does not, by itself, count everyone alive in the region. The duration and organization of work matter.
Later Villages Are a Different Record
The 2020 mound-village study by Iriarte and colleagues documents another architectural tradition in southeastern Acre, broadly dating to AD 1000–1650.
Its settlements include arrangements of mounds around plazas and roads linking villages. Excavated domestic evidence supports their residential interpretation.
These later villages show why the regional history should not be compressed into one timeless map. Similar-looking or nearby features can belong to different periods and serve different purposes.
They also offer evidence against a simple story in which the end of one monumental tradition meant the region became empty.
A Forest with Human History
The central finding is that Indigenous communities substantially shaped parts of this landscape before European colonization. The episode asks viewers to consider forests alongside gathering places, cultivation, and management rather than assume every wooded surface was untouched.
That does not mean every part of Amazonia had identical settlement density or land use.
The strongest answer to the title is therefore qualified: the research supports a large, structured regional landscape, and proposes tens of thousands of earthworks beyond those directly mapped. Testing the total and reconstructing its population remain ongoing questions.
The newly recorded structures are real evidence. Keeping the estimates visibly separate makes that evidence more useful.
Further Reading
- Pärssinen et al. (2026), Nature: Over 20,000 precolonial earthworks in the Southwest Amazonia.
- Nature: Published peer-review record and author responses.
- Iriarte et al. (2020), Journal of Computer Applications in Archaeology: Geometry by Design: Contribution of Lidar to the Understanding of Settlement Patterns of the Mound Villages in SW Amazonia.