Chapter 1: What hidden secrets lie beneath the Amazon rainforest?
The Amazon was one of the least explored places in modern history, but beneath its towering trees and twisting vines lies the memory of a hidden cityscape, a web of buildings, gardens, roads and canals, centuries old, swallowed by the wilderness itself, and for a while, lost completely. But what was once forgotten is now being rediscovered.
Satellite imagery and laser scanning techniques have combined to bring a new version of the Amazon to life. A rainforest that's been shaped by humans for thousands of years, not only through spectacular buildings, but by manipulating entire ecosystems. Networks of creatures that were only just beginning to untangle.
Those creatures make up 10% of the world's wildlife species, and a new plant or animal species is discovered every other day in this great forest. But these aren't the only treasures hidden in the Amazon, whatever came of the lost city of El Dorado. I'm James Stewart and you're watching Astrum Earth. Join me in this video as we venture beneath the canopy to find a different story of the Amazon.
From the early explorers that left clues centuries ago, to the modern science finally deciphering the code to uncover the true secrets hidden in the rainforest. And we'll be answering one big question. What still might be waiting to be found? With 6 million square kilometers of continuous green canopy, the Amazon comprises more than half of Earth's total remaining rainforest.
For centuries, European explorers spread rumors amongst themselves that there was a legendary wealthy city deep in the Amazon. They called it El Dorado, the City of Gold. In 1542, Spanish conquistador Francisco de Orellana reported travelling down the Amazon and finding vast rich lands, with farms, villages, and even large walled settlements.
But when others later followed his route, they found only impenetrable jungle and small groups of hunter-gatherer tribes. Scientists assumed that Orianna's story was just that, a story. Nothing but the fanciful dreamings of a gold-hungry conquistador. But the search for El Dorado did not stop there, and actually it lasted for more than a century.
Established explorers like Gonzalo Pizarro, Philip Von Hutten, and even Sir Walter Riley all led separate expeditions from 1541 to 1617. The result? Well, nothing but disaster, death, and the further conquests of the indigenous people.
But the allure of finding the unfindable endured well into the 20th century too, when British explorer Percy Fawcett became obsessed with finding the riches Oriana had described centuries earlier, fuelled by the fire of one main objective, to find what remained of a lost city he called Zed. He focused on the western Amazon in Bolivia, and the southern Amazon in Brazil, but found nothing.
Along the way he did encounter indigenous people, but found them living in small villages. A far cry from the huge cities the rumours had promised. Rather than deter him, this seemed to spur him on even more. He even wrote to his wife in a letter that she need have no fear of failure.
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Chapter 2: How has LiDAR technology transformed our understanding of the Amazon?
For decades after this last hurrah, really, scientists concluded that this place was simply too hostile, too inhospitable for humans to thrive, and was largely just an expanse filled with exotic flora and fauna. Feedback among the scientific community was that the rainforest soil was so poor it simply could not sustain large-scale farming, and therefore cities were impossible.
But they were all missing something, something that actually Fawcett had been onto. because it turns out he was looking roughly in the right places, but maybe he was looking for the wrong things. Now, up until this point, the rainforest had done a pretty phenomenal job of camouflaging its secrets. But just five years ago, everything changed.
scientists finally found the lost cities of the Amazon, because this time they had something these explorers didn't. They had lasers. Yeah, I know, not what I was expecting to say either, but this is pretty amazing. In the end, the tool that cracked open this mystery is LiDAR, light detection and ranging. Oh yeah, essentially lasers.
LiDAR works by sending pulses of laser light out towards objects, and measuring the time it takes for the reflected laser beams to return. And with a bit of maths, as speed is distance over time, and we know the speed of light, we can then work out the exact distance to those objects.
Over vast areas, taking lots of measurements, that means we can generate precise 3D information about Earth's surface. And in rainforest archaeology that becomes something almost magical. You can scan the canopy and then remove it digitally and then see the ground like the forest isn't even there and what it revealed was astounding.
Now, I should quickly say LiDAR doesn't show us ancient civilizations on its own, but it does show us shapes, microtopography, geometry, the fingerprints of organized earth moving. Then the archeologists go in and do their bit. They excavate, they date stuff, they test the story the terrain is telling.
But as a first step, LiDAR is like looking into your attic with X-ray vision and finding that family heirloom you thought you'd lost without opening a single box. And in the Amazon, it did not disappoint.
In 2022, using this new airborne technology, archaeologist Heiko Pumas and his colleagues mapped settlements associated with the Casarabe culture, which thrived around AD 500 to 1400 in the Llanos de Mojos region of Bolivia. But this wasn't just a splattering of small villages. It was an entire system. They had found a hierarchy, a landscape engineered for humans.
two main sites stood out from the lidar imaging data enormous in area 147 hectares and 315 hectares respectively the size of nearly 400 soccer fields the sites were embedded in a four-tier settlement system with incredibly advanced architecture including platform mounds and conical pyramid-like structures
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Chapter 3: What evidence supports the existence of ancient civilizations in the Amazon?
Now, living things aren't very picky about this and will take in either type of carbon, really, but crucially, carbon-14 is radioactive and so breaks down naturally over time. And what this means is the moment a plant or animal dies, the clock starts, effectively. It stops taking in carbon-14, and as it decays, the amount of carbon-14 in the organism decreases.
Its half-life, therefore, that's the time taken for half of the carbon-14 in a sample to decay, is around 5,700 years. As such, scientists can measure what percentage of the carbon in a sample is still carbon-14, and from that, can calculate how many years have passed since that organism died, which is pretty clever. When used in tandem, these two techniques reveal incredible things.
Think of LiDAR as finding the where and the radiocarbon dating determining the when. As amazing as all these discoveries undoubtedly are, they are just zoomed in examples of the mysteries the canopies hid, and they're hints of something far larger. Really, Bolivia and Ecuador were just the close-ups. The next step is the wide shot, and here, here's where things get wild.
In 2023, Brazilian geographer and remote sensing specialist Vinicius Peripato did something pretty bonkers. He applied this same concept, but on a far larger scale, taking an Amazon-wide approach to hidden archeology.
He and his team used LIDAR data originally collected for forest biomass work and scanned 5,315 square kilometers across the basin, which, yes, might sound impressive, but remember, this is the Amazon. That's roughly 0.08% of the whole thing.
But here's where it gets interesting, because even in that tiny slice of this monstrous green pie, they identified 24 previously undetected earthworks beneath the closed canopy. Now, if you were to apply those same numbers to the unscanned parts of the rainforest, they estimated there are between 10,272 and 23,648 large-scale earthworks still
still waiting to be discovered, with many likely concentrated in southwestern Amazonia. What? Peripato's team also found statistical links between earthwork probability and dozens of domesticated tree species, 53 to be precise. What this means in real terms is that ancient people shaped the forest. The species that increased near earthworks were very likely planted protected and even encouraged.
This part of the Amazon shows huge long-term human influence. If, if these predictions hold true, it just goes to show that hidden doesn't necessarily mean mythical. It means not yet measured at the right resolution, in the right dimension and by the right method. And speaking of, there is still one place that so far eluded all of these scientists. Do you know what I wish would elude me?
Data brokers. Those annoying people that are more than happy to sell my personal info to the highest bidder. Things like my email address, home address, and family information. Trust me, this is one instance I'd love to stay hidden like one of these Amazonian cities. No matter where I go, they always seem to find me. Maybe they're using LiDAR too, come to think of it.
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Chapter 4: What was the significance of the legendary city of El Dorado?
The link is in the description if you want your digital life a bit more private as we head back to El Dorado. Yeah, we touched on this place right at the start of the video and it turns out the reason we cannot see it is because it never existed. Yeah, sadly for all of those would-be treasure hunters, the gold one was actually not a place, but a person.
The name comes from the Muisca people, who lived high in the Andes of modern day Colombia from AD 500 and still do to this day actually. To the Muisca, gold wasn't a symbol of wealth or private treasure. It had a deeper meaning, it was sacred. During rite of passage ceremonies, a new ruler, known by the Spanish as El Dorado or the Golden One, would undergo a dramatic ritual.
His body would be covered head to toe in gold dust, and he would set out on a raft into the centre of a sacred lake, most famously Lake Guatavita, 75km northeast of what is now the capital, Bogota. Once in the center, priests and attendants would cast gold and precious other things into the lake as offerings.
Then covered in gold, the ruler might submerge himself into the water and return to shore with the remaining dust washed off his skin and remaining in the water. When Spanish chroniclers like Juan Rodriguez Frele in the 16th century shared these second-hand stories, over many centuries, stories of immense gold offerings and dazzling ceremonies became more than just decorated leaders.
They turned into a whole city full of treasure that Europeans just sort of reimagined. Soon the idea had taken on a life of its own, and just as cartographers redrew maps to include lost cities like Atlantis, the name El Dorado also started to appear. Fortunately though, science eventually intervened, and remarkably a gold raft depicting the exact scene we've just described
was found in 1969 by three villagers. It was hidden away in a small cave in the hills, showing the man covered in gold going out into a sacred lake, the real story of El Dorado. So yeah, in the end scientists weren't able to uncover a city of gold, but they did find something arguably way more valuable.
Now we go deeper, literally, because one of the Amazon's strangest secrets isn't in a wall or a road, but instead is its soil. Bear with me here. I know that doesn't sound as exciting, but trust me, it is.
Because if humans lived in all those amazing sites we've showcased in this video, which does seem very likely, how did they exist in spite of the rainforest's naturally poor and nutrient-depleted soil? How did they grow stuff? It's impossible, right?
Remember at the start of the video, when we said all of those expeditions, right from the 1500s to poor old Percy Fawcett in 1925, all of those had scientists saying part of the reason the cities couldn't be found was because the soil was too infertile to support human life. Remember that?
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