Lost civilizations of the Americas: terra preta, arrowheads and the first Americans

The Short Version

The Amazon rainforest, the American plains and the Central American jungle all look like wilderness, but none of these conversations treats them as untouched. On Joe Rogan's episode with Dr. Mark Gordon, Rogan describes terra preta, a dark soil in the Amazon that he says ancient people made on purpose, and lidar scans showing street grids and water systems where millions of people may once have lived before European diseases killed them and the jungle grew back [1]. Steven Rinella explains how the story of the first Americans has been rewritten, from a single ice-free corridor to a fast "kelp highway" down the coast [2]. Michael Waddell describes picking up arrowheads that are thousands of years old and hunting turkeys beside an unexcavated Mayan pyramid [3]. Paul Rosolie shows that people still live in the deep Amazon: uncontacted tribes whose fearsome reputation is part of why their river stayed wild [4]. The pattern is the same in every case. What looks like pristine nature often sits on top of, or grew out of, a long human past, and much of that past is still being found or is still alive.

Table of contents

What They Said

Joe Rogan and Mark Gordon: terra preta and the lost cities of the Amazon

The terra preta discussion begins with a detour. Rogan and Gordon are talking about organic farming, and Rogan reads an article about the German explorer Alexander von Humboldt finding heaps of bird droppings in Peru in 1802, which set off a worldwide fertilizer rush and even wars [1]. Fertilizer reminds Rogan of something Graham Hancock told him. Although the episode is billed as Gordon's, it is Rogan who explains terra preta, and he gives Hancock as his source [1]. "There's a very specific soil in the Amazon that they think people from thousands of years ago figured out how to make," Rogan says, calling it "some sort of a compost process" that produced "a very dark soil" [1].

Rogan's central claim is that the soil is artificial: "this dark soil that exists on the surface layer of a lot of the Amazon was put there by man. And not just put there by man, but created" [1]. He adds that the method has been lost: "If they had a process that they have not replicated to this day, they don't know what it is or how they did it" [1]. He is careful about where this comes from. When the claim comes up, the transcript records "At least that's what he said. Well, that's what he said," before he shows Gordon a picture [1]. In the image, he points out, "the terra prada is on the surface and then you go below it and you just get like regular dirt," and this rich layer "grew so much plants" [1].

He then makes a bigger claim about the forest itself: "do you know that the Amazon is mostly human planted plants that grew out of control?" [1]. His picture is of a region whose earlier inhabitants shaped it. Researchers, he says, "used to think that it was just this crazy wild jungle and there's indigenous populations to live inside of it," but "one point in time there were cities" [1]. The evidence he gives is lidar scans from drones and aircraft, which reveal "grids that indicate there were structures there," signs of "some sort of transportation of water," and what "looked like streets" [1]. From these geometric patterns, he says, researchers now think "there were millions of people living in the Amazon and that what probably happened was Europeans came over and gave them all smallpox" [1]. He puts the losses in stark terms, "90% of Native Americans," and explains why the evidence disappeared so completely: because of the constant rain and the speed of growth, "as soon as they were gone within a couple hundred years, everything's consumed by the jungle" [1]. What remains are "large sections of the Amazon that have these patterns and structures that indicate civilization" [1].

Gordon mostly listens here, but he adds his own interest. He says he spends his mornings looking at archaeology, mostly lidar work in Europe, because he collects ancient coins from Italy, Germany and Spain [1]. The summary counts this among the episode's loose, curious tangents, with Rogan repeatedly checking claims in real time [1].

From the lost cities, Rogan moves to the people who live in the Amazon now. "There's a bunch of different uncontacted tribes that live in there," he says, and brings up his friend Paul Rosolie, who hires former loggers to protect the forest and who "runs in the uncontacted tribes all the time" [1]. Rosolie had sent him a video he could not share. Rogan describes "naked people in the jungle in 2025" and says they "lived the way people lived 100,000 years ago" [1]. The conversation turns to the obvious question: "They live in isolation. Well, isolation from what? From us?" [1]. Rogan imagines filming them with drones disguised as insects, then sees the problem himself: people "would want to go visit them," and that would ruin everything [1]. That is why Rosolie keeps the video private, and Rogan adds that "one of his friends was murdered by these people" [1].

The episode also touches on the question Rinella answers in depth: who the first Americans were. Rogan questions the label "Native American" by asking "Native for how long?" and brings up the Bering land bridge theory [1]. He tells the story of a wealthy Mormon who paid for DNA testing of Native Americans, expecting it to show descent from the lost tribes of Israel, and learned instead that "they're from Siberia, like a lot of them are from Siberia" [1]. The two also read an article arguing that the word "Indian may come from a Spanish phrase, los niños in Dios," the children of God, and not from Columbus thinking he had reached India, since, the article says, the country was then called Hindustan [1]. The summary presents this as an article's argument, not a settled fact [1].

Steven Rinella: who the first Americans were, and how archaeology is changing

Rinella brings the most historical detail and the most scholarly caution. When Rogan asks where he would go with a time machine, he chooses the moment the first people entered the Americas [2]. He starts with the old model: people crossed a Bering land bridge the size of Texas, were held in Alaska by ice, and then came through an ice-free corridor near Edmonton onto the Great Plains to hunt mammoths [2]. That timeline, he says, can no longer hold, because older sites have turned up, including Monte Verde in Chile and the oldest widely accepted site, in the Columbia River drainage [2].

The idea in favor now, he says, is the kelp highway: a seafaring people who followed coastlines rich in kelp beds south with great speed, then moved inland up salmon rivers, and only later became mammoth and grassland hunters [2]. This changes the picture. The first Americans come by boat along a productive shore, not only on foot across an icy plain.

Rinella also describes new evidence about Clovis people, the famous early mammoth hunters. Isotope work on the Anzick child, a Clovis-era burial from Montana, shows a diet that included woolly mammoth, which supports archaeologist David Meltzer's view that Clovis people really hunted mammoths and were not mostly scavengers and plant gatherers [2]. Rinella took part in an experimental archaeology study at Kent State University, butchering a bison with stone flakes and Clovis points to build a reference set of cut marks, because at old sites "the only thing left is bone and stone" [2]. The results were surprising. Removing the tongue left none of the jaw marks long assumed to come from tongue extraction, and Rinella now wonders whether Clovis points were sometimes used as knives [2].

He also offers a reason the continent filled so quickly. Fresh carcasses are rarely just lying around, he argues, and animals that had never seen humans could probably be approached and killed easily [2]. In the transcript he imagines one of those animals looking at a person and thinking, in effect, what is this tiny thing going to do, and says "that was an idea that pushed like how fast people spread around" [2]. With so much food, the early arrivals "weren't fighting each other," and were "enjoying like very high reproductive rates because they're drowning in food and there's no conflict" [2]. Rogan wonders how big the wildlife populations were back then, and both answer "Staggering" [2].

The most useful part of Rinella's contribution may be what he says about method, because it explains why our picture of the past keeps changing. Scientists, he notes, "can go into pond sediments" and find DNA from shed cells, and might identify "skin cells from six mammoths short face bear" in a sample from ten feet down [2]. He sees the field shifting from the Indiana Jones image toward the lab: "archaeology is becoming increasingly anthropology," and it is now a richer field "to analyze stuff we already have then it is to go find new stuff" [2]. Digs now leave most of a site alone on purpose: "if we got a hundred squares we'll just dig one now" [2]. Older excavators, he says, would hose sites down looking for big bones and big points, and "you'd come away with thinking that they use big stone points to kill big bones because you just washed into the ditch all of that micro evidence all of those small bones all the plant pollen" [2]. His humility covers the present too: "so we probably make the same mistake now" [2].

Rogan brings up his friend John Reeves's Alaskan bone yard, a six-acre site with "thousands and thousands of bones" in the permafrost, under a thick layer of carbon that Reeves thinks points to a natural disaster, perhaps an asteroid impact [2]. Rogan says "they found animals that weren't even supposed to be in Alaska there" and that they "may or may not have found human remains there" [2]. Earlier, Rogan had also raised the Sage Wall in Montana; Rinella thinks it is probably natural but may cover it in a future episode [2].

Rinella ends on the hardest subject: whose past this is. He describes meeting a man from one of the New Mexico pueblos who works to bring his ancestors' remains home from museums. When Rinella suggested a museum might keep a gram of bone for study and return the rest, the man said "that would never be acceptable to us," comparing it to someone digging up your grandfather [2]. Rinella sees a real puzzle with very old remains: "when you're talking about bones that are 10 11 12 thousand years old," it can be hard to know who the direct descendants are, because "people moved all over" [2]. He draws a clear line for the pueblos, though: they are "people that have had occupation on these places for hundreds of years and people just came and hauled their ancestors out" [2]. He describes a Chicago museum exhibit covered in paper during a repatriation dispute, and a visit to Salta in Argentina to see one of three Inca children left on a mountaintop, preserved so well that even the feathers were intact. Only one is shown at a time under an agreement with Inca descendants, and "you're looking at someone's baby" [2].

The Donner Party thread in the same episode makes a related point. Rinella notes that one man murdered two Native American guides to eat them and was never punished, because "It was more illegal to kill someone's cow than it was to kill two Native Americans" [2]. It is a reminder that the human history of these landscapes includes violence toward the people who were already there.

Michael Waddell: arrowheads, buffalo jumps and a pyramid in the jungle

Waddell comes at deep history as a hunter, through objects and places. For him, finding an arrowhead makes the past something you can hold. "When you find one of those, you're picking up this piece of history," he says. "You gotta imagine some Native American was napping this flint on his knee" [3]. He talks about the age of these points with wonder: "They find 3,000, 4,000 year old arrowheads and you just gotta go, God, what was life like that, man?" [3]. He notes local differences too. "All the airheads I find are quartz. So we have very little flint," he says of Georgia, and he admits "I'm not at all historically sound on understanding everything" [3]. He mentions his neighbor Jeff Foxworthy, who "is obsessed with Indian artifacts and has an amazing collection" [3], and warns that forgeries are common now [3].

He also describes a whole landscape used by ancient hunters: a Montana ranch on the Milk River with a buffalo jump, where hunters wounded bison with small points and drove them off a cliff [3]. The landowner banned cameras so the site would not become a historical site [3], which is one way these places stay hidden. Rogan adds that at such sites the pile of rotting bison could get so big it caught fire [3]. Butchering an elk, Waddell says he complains less about resharpening his knife when he remembers that earlier hunters had to knap every blade from stone [3].

His most striking story comes from the jungles of southern Mexico. On an ocellated turkey hunt with Troy Link of Jack Link's jerky, he found himself calling turkeys next to an unexcavated Mayan pyramid [3]. "You got all that Mayan civilization and all this stuff that I saw, even Graham Hancock," he says, but "what people don't realize, we're out in the middle of this jungle and I'm walking around" [3]. His guide just shrugged that such ruins are everywhere, and outfitters keep quiet about them because it is their hunting ground [3]. During the episode, Jamie pulls up the recent lidar discovery of a lost Maya city, called Valeriana, in Campeche [3]. It is the same technology Rogan describes in the Amazon [1], now used on another forest.

The conversation also includes Graham Hancock's bigger thesis, which Rogan summarizes. "There's real physical evidence that something happened around 11,800 years ago, that the earth was most likely pounded with asteroid debris," Rogan says [3]. He describes Hancock's interest in "the real evidence that there was really sophisticated societies that lived thousands and thousands of years ago, when we kind of assumed that people were hunters and gatherers," and Hancock's belief that such a society "had reached a very sophisticated level of technological achievement and then something happened. And now we're living in like a rebuild" [3]. Waddell says he binged Hancock's Netflix series after hearing him on the show and calls it "pretty amazingly compelling" [3].

Waddell connects the ancient past to living Native communities. He hunts often with the Navajo Nation and says "they become like family to me" [3]. Every year, with the Navajo Nation's game and fish department, "We take 15 to 20 Navajo youth hunting," and he laments that "even amongst the Native, some of that culture is being lost" [3]. He also traces modern bowhunting back to Ishi, a Native American from California who taught the doctors Saxton Pope and Art Young to hunt with a bow, inspiring the Pope and Young Club [3]. So even the sport's modern record books go back to Native knowledge.

The Bigfoot talk at the start of the episode fits the theme in a skeptical way. Rogan says I think hunters are the number one argument against big foot being real, because trail cameras are everywhere and nobody has a single photo [3]. He does note that Gigantopithecus was real and lived around a hundred thousand years ago [3]. The episode keeps a line between what the ground actually yields, such as arrowheads, buffalo jumps and pyramids, and what remains speculation.

Paul Rosolie: the forest that is still inhabited

Rosolie's conversation with Lex Fridman, recorded at night deep in the Peruvian Amazon, is mostly about wildlife, but it is the one source where the human history of the wild is still living [4]. Rosolie has spent 18 years protecting a remote stretch of rainforest along the Las Piedras River with indigenous conservationist Juan Julio Durand (JJ), through the group Junglekeepers [4].

He describes the uncontacted tribes near his work as living naked and nomadic, without even stone tools [4]. His explanation for their violence is historical: it comes, he believes, from rubber-boom atrocities a century ago, which taught them that outsiders were trying to kill them [4]. He also says their fearsome reputation is why this river stayed wild [4]. That turns the usual idea around. The Las Piedras is wild not because people never lived there, but partly because the people who do live there have kept outsiders away. He gives one example: a local man who tried to give them plantains was shot in the skull with a seven-foot arrow and survived [4]. Rosolie calls protecting them a human rights issue [4].

His conservation plan builds on this. About 30 million dollars over the next two years, he says, could create a corridor linking uncontacted-tribe reserves with national parks into one of the largest protected areas in the Amazon [4]. The region lies between Manu National Park, Alto Purús and Tambopata, and it is threatened by roads, by logging companies working as subcontractors for international corporations, and by gold mining, which Fridman links to the trafficking of teenage girls [4]. Junglekeepers helps local and indigenous people protect their own forest, such as a community that fought for 20 years for land titles, and it hires former loggers as rangers; his friend Pico used to log full time and now loves conservation [4]. Protected land has grown to 66,000 acres [4].

Rosolie's broader point is how much of this forest's knowledge depends on people. Explorers of Percy Fawcett's generation, who vanished in 1925 searching for a lost city, called the Amazon a green hell because they arrived with mules instead of locals. To JJ it is green paradise, full of turtle eggs, grubs and fish [4]. Rosolie praises Harvard ethnobotanist Richard Evans Schultes for embracing indigenous knowledge, and mourns that much of that plant knowledge was lost in a single generation of modernization [4]. Locals believe the ayahuasca recipe, one vine combined with one plant out of tens of thousands, was revealed by the gods rather than found by trial and error [4]. The forest, in his account, is a place people have long lived in and understood, and that knowledge is disappearing faster than the trees.

He also stresses how little outsiders know. For most of the region's roughly 1,500 butterfly species, no one knows which plants their caterpillars eat, and about half of rainforest life lives in the canopy, which scientists have reached with ropes, slingshots and even hot-air balloons [4]. Junglekeepers rangers contributed a first record of pygmy marmosets on the river to a mammal paper [4]. A forest this poorly surveyed can easily hide ruins, soils and people.

Where They Agree, and Where They Don't

They agree that "wild is a misleading word. Rogan says the Amazon was once thought to be just this crazy wild jungle" and now appears to have held cities [1]. Waddell walks past a Mayan pyramid in what looks like empty jungle [3]. Rosolie's river stayed wild partly because of the people living in it [4]. Rinella shows the whole continent was settled by people who spread quickly through lands full of animals that had never seen a human [2]. Each speaker describes a landscape where humans were, or still are, part of the scene.

They agree that new tools are revealing the past. Lidar appears twice, over the Amazon [1] and over Campeche's lost Maya city [3]. Rinella adds isotope analysis, sediment DNA and experimental butchery [2]. All of them suggest the full picture is still coming into view.

They agree that much of this history is hidden, sometimes on purpose. Rosolie keeps his video of the tribes private so people won't go looking for them [1]. A Montana landowner banned cameras at his buffalo jump [3]. Mexican outfitters keep quiet about ruins on their hunting grounds [3]. Archaeologists now leave most of a site untouched for future tools [2]. Repatriation disputes put museum displays behind paper [2]. The reasons differ, from protecting a tribe to protecting a hunting spot to respecting the dead, but the result is the same: the public sees only part of what exists.

They differ in how much confidence they give to bold claims. Rogan presents terra preta as a lost technology whose process "they have not replicated to this day," but he credits the claim to Graham Hancock and adds "that's what he said" [1]. He also passes on Hancock's thesis of an advanced civilization set back by an asteroid 11,800 years ago, and Waddell finds it compelling [3]. Rinella is much more careful. He thinks the Sage Wall is probably natural [2], and his main lesson about archaeology is that past experts misread sites because they found only what they were looking for, and "we probably make the same mistake now" [2]. The sources don't directly contradict each other, but they show two attitudes: one open to dramatic lost-civilization stories, and one that insists on bones, stones, cut marks and isotopes. Readers should notice that the most specific evidence here, the Anzick child's diet and the Kent State cut-mark study, comes from Rinella [2], while the terra preta claims come second-hand through Rogan [1].

They tell the tribal-violence story differently. In the Gordon episode, Rogan says one of Rosolie's friends was "murdered" by an uncontacted tribe [1]. In Rosolie's own account, a local man who tried to give the tribe plantains was shot in the skull with a seven-foot arrow and survived [4]. These may be two different incidents, and the sources don't say. Rosolie also gives the history behind the violence, the rubber-boom atrocities [4], which Rogan's version leaves out.

They see the human stakes of this history differently. Rogan's account of the Amazon is mostly wonder and loss: millions of people probably killed by smallpox and swallowed by the jungle [1]. Rinella stresses the ethics of who owns the remains and the difficulty of tracing descent across 10,000 years [2]. Waddell worries that Navajo culture is fading among the young [3]. Rosolie treats living tribes as a human rights issue that needs land protection now [4]. Put together, they move from ancient ruins, to disputed bones, to fading traditions, to people alive in the forest today.

Why It Works

The sources give several mechanisms that explain how a landscape can look untouched while carrying a deep human past.

Fast regrowth erases visible traces. Rogan's explanation is that the Amazon rains constantly and plants grow so well that "within a couple hundred years, everything's consumed by the jungle" [1]. A civilization wiped out by disease would, from the air, soon look like virgin forest. Rosolie's description of the jungle as "a giant churning machine of death" in which life is "kind of this moment of stasis" [4] suggests the same speed of turnover.

Epidemics emptied the land before most outsiders saw it. Rogan says Europeans probably "gave them all smallpox," killing "90% of Native Americans" [1]. If most people died before explorers arrived, later visitors would have found a thinly settled forest and taken that as its natural state.

People reshaped the soil and the plants. According to Rogan, terra preta is a surface layer that sits on top of "regular dirt," and it made the land rich enough to grow abundant plants [1]. His claim that much of the Amazon is "human planted plants that grew out of control" [1] describes a forest that is partly a garden gone wild. These claims come to us through Rogan, who got them from Hancock, and the sources give no further evidence for them [1].

Seeing through the canopy takes new instruments. Lidar from drones and planes reveals "geometric patterns that exist below" the trees [1], and it found the Maya city in Campeche [3]. Rosolie notes that half of rainforest life is in a canopy scientists could barely reach [4]. Until these tools existed, what lay under the trees stayed invisible.

Old methods destroyed evidence and shaped wrong conclusions. Rinella explains that hosing sites down for big bones and points washed away the "micro evidence," small bones and pollen, and led to simple ideas about how people lived [2]. His experiment showed that marks long assumed to come from removing tongues did not appear when he removed one with stone tools [2]. Better methods, such as isotopes, sediment DNA and replication studies, keep adding human history to places and periods once thought empty or simple [2].

Isolation and fear keep people out. Rosolie's account shows that uncontacted tribes stay uncontacted partly through violence born of past atrocities, and that their reputation kept loggers and settlers off the river [4]. Rogan adds that publicity would draw visitors who would ruin everything [1].

Untouched animals help explain how people spread. Rinella's argument that animals which had never seen people were easy to approach and kill, leaving the first Americans "drowning in food" with "no conflict," is his explanation for how fast people spread across two continents [2]. It suggests humans reached even remote places early, so few places in the Americas lack a human past.

Where It Applies, and Where It Doesn't

Where it applies. The pattern is strongest in the Amazon, where lidar grids, terra preta and living tribes all appear [1][4]. It applies to the Maya lowlands, where ruins lie unexcavated under jungle and a lost city was recently found by lidar [3]. It applies to the Great Plains and the Rockies, where buffalo jumps, Clovis sites and arrowheads mark thousands of years of hunting [2][3]. It applies to Alaska and the Pacific coast, where the first Americans may have traveled the kelp highway and where Reeves's bone yard holds a buried record of ancient animals [2]. It applies to the mountains of Argentina, where Inca children were left on a peak [2].

Where it is less certain. Not every claim here is equally supported. The terra preta and "mostly human planted" statements reach us second-hand from Hancock through Rogan, who adds his own "that's what he said" [1]. Hancock's asteroid and lost-civilization thesis is presented as his belief, and it is Rogan and Waddell who find it compelling [3]. Rinella's warning that archaeologists may be making mistakes today [2] applies to bold new theories as well as old ones. Rinella also thinks the Sage Wall is probably natural [2]. Seeing human history everywhere carries its own risk: sometimes a structure is just geology.

Where it doesn't apply. The sources don't claim that all wild places are really human-made, or that wildlife and wilderness don't matter. Rosolie's conversation is largely about animals, ecosystems and species science hasn't recorded [4]. The Bigfoot discussions show the speakers can separate real deep history from legend: Rogan calls hunters the number one argument against big foot being real [3], while granting that Gigantopithecus existed [3]. The pattern also doesn't settle ownership questions. Rinella points out that 10,000-year-old remains raise real doubt about who the descendants are, while the pueblos have a clear claim [2].

A caution about the word "untouched." Rogan's phrase for the tribes, people who "lived the way people lived 100,000 years ago" [1], can make it sound as if they are outside history. Rosolie's account suggests the opposite. Their way of life and their hostility to outsiders were shaped by the rubber boom a century ago [4]. Their isolation is a response to history, not a place outside it.

What To Do With It

1. Rethink "pristine." When you see a rainforest, a prairie or a jungle, remember that the sources describe cities under the Amazon [1], pyramids in Mexican jungle [3], buffalo jumps on Montana ranches [3] and people spreading across the continent more than 10,000 years ago [2]. Assume a human past until someone shows otherwise.

2. Follow the lidar discoveries. Lidar surveys revealed the Amazon's grids and water systems [1] and the Maya city of Valeriana in Campeche [3]. Following new lidar results is a direct way to watch this history come to light.

3. Update your picture of the first Americans. Rinella says the ice-free-corridor model is out of date because of sites like Monte Verde and the Columbia River drainage, and that the kelp highway is the idea in favor now [2]. When you read or teach about the peopling of the Americas, include the coastal route and the evidence behind it.

4. Weigh sources by the kind of evidence they give. Separate claims backed by physical tests, such as the Anzick child's isotopes and the Kent State cut marks [2], from second-hand accounts like the terra preta claims Rogan credits to Hancock [1]. Keep Rinella's warning in mind: "we probably make the same mistake now" [2].

5. If you find artifacts, leave the context intact. Rinella explains that small bones and pollen are the evidence that gets lost when sites are dug carelessly, and that digs now open only one square in a hundred so future tools can learn more [2]. Waddell warns that forgeries are common [3]. Treat an arrowhead as part of a site, not only a souvenir.

6. Respect descendant communities' claims. The pueblo representative's answer, "that would never be acceptable to us," to keeping even a gram of bone [2] shows that for descendants, remains are ancestors, not specimens. When you visit museums, as Rinella did in Chicago and Salta [2], pay attention to repatriation disputes and the agreements that govern what is shown.

7. Support the people who keep living history alive. Waddell takes 15 to 20 Navajo youth hunting each year to help keep their traditions going [3]. Rosolie's Junglekeepers helps indigenous communities secure land titles and pays local people, including former loggers, to protect their forest [4]. Rosolie tells of a single mother who gives five dollars a month with her kids, saying "I saw how a few million raindrops can create a flood" [4].

8. Leave uncontacted people alone. Rogan and Rosolie both treat privacy as protection. Rosolie won't release his video because people would go looking [1], and the tribes' violence comes from past atrocities by outsiders [4]. Support land protection, such as the corridor Rosolie proposes linking tribal reserves and national parks [4], rather than trying to see or contact them.

9. Learn from indigenous knowledge before it disappears. Rosolie mourns that much Amazonian plant knowledge was lost in one generation, and he praises Schultes for taking it seriously [4]. Waddell notes that modern bowhunting goes back to Ishi [3]. Read the people who recorded this knowledge, such as Wade Davis's One River, which Rosolie recommends [4].

10. Keep curiosity and skepticism together. Rogan checks claims in real time and admits when a claim is second-hand [1]. Rinella is willing to cover the Sage Wall while thinking it is probably natural [2]. That combination is the best way to explore lost civilizations without falling for every story about them.

Sources

1. Dr. Mark Gordon · The Joe Rogan Experience
2. Steven Rinella · The Joe Rogan Experience
3. 2248 - Michael Waddell · The Joe Rogan Experience
4. Paul Rosolie: Jungle, Apex Predators, Aliens, Uncontacted Tribes, and God · Lex Fridman Podcast