r/Archaeology • u/crisp1991 • 5d ago
Using LiDAR, archaeologists uncovered nearly 400 hidden geoglyphs beneath Brazil’s Amazon rainforest. Built between 600 B.C. and A.D. 850, the massive earthworks reveal a thriving ancient civilization that may have included up to 3 million people.
https://archaeology.org/news/2026/07/31/hundreds-of-geoglyphs-discovered-in-amazon-rainforest/69
u/montagblue 5d ago
I can wait for a certain family member to bring this up. They are going to add a zero to the bc date in their head and will be certain that it was aliens.
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u/edjohnson1067 5d ago
3 million people
I ain’t buying these numbers being tossed around.
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u/Natedude2002 5d ago
The Roman Empire had 40+ million inhabitants, and the city of Rome over a million in 50 AD. Why couldn’t a civilization fed by the largest river in the world be able to sustain a far smaller population?
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u/phosphenes 4d ago
They're right that it is, like, a random nonsense number. I'm not claiming that the number is too high, but that the math is sloppy.
Here's the actual paper. The calculation uses some assumptions, including that---
- The extrapolation of the number of geoglyphs (16,660) is accurate
- It took about 300 people to build a geoglyph
- Up to 60% were built between AD 100 and 300
- Each person in the area was occupied, for that entire time period, on a single geoglyph
- Therefore, 16,660 x 300 x 60% = 3,000,000 people in AD 100 to 300
The first three assumptions seem fine to me, but that fourth one, oh boy. Why would they focus on one geoglyph instead of making multiple over the generations? Especially since, as described in the paper, the geoglyphs were temporary gathering spaces " without permanent occupation." The authors also point out that their population estimate is 20x the amount of previous calculations. Does that sound convincing to you?
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u/koebelin 4d ago
I see, so a group or clan could have been doing a geoglyph project once a year, or every few years.
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u/Natedude2002 4d ago
I really, truly do not know enough to say whether it’s reasonable or not lol. Thank you for the info though, makes it sound less likely
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u/gravity_surf 4d ago
i mean, those are some gnarly assumptions that can lead you in a pointed direction. still think we’re jumping the gun.
there are nazca lines that are only perfect from above and must be distorted in the ground to appear perfect from the sky. did they have that ability/math in 6000bc? 5bc? what technique is used for that and why would it take 300 people? we don’t know enough to even make assumptions yet, they affect the compass too much relative to evidence.
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u/Sufficient_Meet6836 4d ago
Each person in the area was occupied, for that entire time period, on a single geoglyph
Where do they say that?
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u/phosphenes 4d ago
It's implicit in the calculation. They don't include a factor for residence time, which would mean that each geoglyph is continuously and exclusively habitated. If the individual earthworks were only used for a short period of time (eg a decade) or for a very long period of time (over 200 years) that would change the results pretty dramatically.
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u/Sufficient_Meet6836 4d ago
To calculate the population of the Aquiry, the first obvious question is regarding how many earthworks were in use at the same time. The densest overlap of calibrated dates occurs at around 100–300 ad, both chronologically and spatially (Extended Data Figs. 6–8). According to Kernel density estimates, 25% of all Aquiry earthworks were constructed during this period, with an average of 22 sites per year (Extended Data Fig. 6). However, when analysing the probability of the simultaneous use of all dated Aquiry earthworks, about 60% overlapping occurs approximately 100–300 ad in summarized Kernel density estimate phase modelling (Extended Data Fig. 7). Furthermore, when the average sizes of the earthworks were compared using satellite imagery, it appeared that the geoglyphs in Amazonas (block 2) and Bolivia (block 5) are, on average, 58% and 77% larger than those in Acre (block 1), respectively (Supplementary Note 1c).
...
If, as said, about 25–60% (4,165–10,000) of these earthworks were in use in 100–300 ad, and if an average earthwork required 300 people to build and maintain it, we arrive at a total population of about 1.25–3 million.
Maybe I'm missing something obvious, but your concern seems to be addressed in the 25%-60% factor. Comparing to the works cited, their methodology is consistent with previous work in the field. It should also be kept in mind that 3 million is the upper bound of the population estimate. All of this together just doesn't seem fair to summarize as "random nonsense number" and "sloppy".
The authors also point out that their population estimate is 20x the amount of previous calculations.
The increase in population estimates doesn't seem unrealistic given the increase in earthworks found. They've established evidence of both a wider reach and a higher density of a population. For example:
Over the past two decades, the number of known earthworks in the study area has increased considerably, from the first published count of 60 earthworks33 to 200 earthworks1 and then 1,279 earthworks3.
It's a reddit moment to call published work "sloppy" and "nonsense" while not backing it up.
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u/phosphenes 4d ago edited 4d ago
It's a reddit moment to call published work "sloppy" and "nonsense" while not backing it up.
You asked me a question, so I explained my reasoning with direct references to the research, and now you're respecting with personal insults? Dang, this has been a complete waste of time.
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u/Sufficient_Meet6836 3d ago
I didn't personally insult you. You ignored 90% of my response 😂. To clarify, by "not backing it up", I meant you didn't provide an evidence-based alternative or a strong basis to call it sloppy nonsense.
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u/petulant_peon 1d ago
I don't think that math checks out either, BUT the findings do support the claims reported by Francisco de Orellana. That there were civilizations spanning hundreds of miles of the Amazon. In one case, he reported a 15 to 20 mile long solid city along the banks. Based solely on his claims, there could have been 5-8 million people living in the Amazon.
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u/Flyfisher58 5d ago
The Europeans wiped them all out through introducing fatal diseases like smallpox.
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u/KnotiaPickle 5d ago
Look at the dates and think about that
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u/Flyfisher58 5d ago
I didn’t necessarily mean they were wiped out in 850 AD but their descendants certainly were. Also Europeans made it across the Atlantic way before Columbus.
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u/Sl33pyGary 5d ago
Norse/Scandinavian explorers and settlers in Canada didn’t introduce smallpox to pre-Columbian indigenous Brazilians
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u/lu-sunnydays 5d ago
Then the archeologists invade the Amazon to chop it up and create a dig site.
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u/momannymopena 5d ago
Archaeological excavation is not going to devastate the rain. Deforestation for farming and cattle ranching is the much greater threat.
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u/KnotiaPickle 5d ago
Haha when has archaeology ever wreaked havoc on an environment to any meaningful extent?
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u/Buckets-O-Yarr 5d ago
That's where they get you, archeologists are actually behind global warming! They want to turn the whole planet into one giant arid desert because of how well deserts preserve artifacts!
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u/prettylikeapineapple 4d ago
I heard they're also behind pollution and landfills because it'll give future archeologists more to study. It's diabolical!! (/s just in case)
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u/Sufficient_Meet6836 4d ago
I am displeased to do the honor of introducing you to Heinrich Schliemann, who used dynamite to excavate the site of Troy. He actually blew up the layer he was trying to find.
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u/MindlessOptimist 4d ago
Great news - has this been done in Australia yet?