513: DEEP DIVE: Are Humans the First Civilization? The Silurian Hypothesis
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There are over 8 billion people living on the earth right now. Tens of millions are born and die each year. Every single one of us leaves signs of our existence in the air, water, soil, even space. But these signs won't last forever. Our buildings will be gone in a few hundred years. Our stone monuments, plastics, styrofoam, twinkies, even evidence of our nuclear destruction will eventually be gone.

So if there's a time in the future where there's no evidence of our civilization, how can we be sure there wasn't an advanced civilization before us? Well, according to the Silurian hypothesis, we can't.

The Silurian hypothesis was named after intelligent humanoid reptilians from the show Doctor Who. After hibernating underground for 400 million years, they were awakened by a nuclear test on the surface. After they woke up, there was a standoff for control of Earth between the Silurians and humans. Did Doctor Who accidentally get it right?

Humans are selfish. It's hard for us to imagine that in a very short time, we as individuals won't be here. It's even harder to imagine a time where our civilization won't exist at all.

But if we've learned anything from archaeology, it's that every civilization has its time. Think about ancient Egypt. They lived through 30 dynasties that spanned over 3,000 years. If you were an Egyptian living during this time, generation after generation of your family going back as far as anyone could remember walked in the shadow of the pyramids.

They fished the Nile. They sailed the Mediterranean and mingled with other cultures. As far as you or anyone knew, your civilization had been there and would last forever.

and then it was gone. The Mesopotamians before then, the Indus after them, the Greeks, Nubians, Persians, Romans, Incas, Aztecs. These were empires of millions of people, all lasting a thousand years or more, but very little evidence of them remains. All of these civilizations, including our own modern one, have only been here for a short time.

Complex life has existed for hundreds of millions of years. Modern humans have only been here for about 200,000 years. Our entire history has taken place in the past 0.002% of life on Earth.

So there's a whole lot of past in the past. That's plenty of time for other intelligent species to evolve, thrive, and then go extinct over and over again with different species. And if that happened, would we really know they were here?

When Adam Frank and Gavin Schmidt wrote the Silurian Hypothesis, they addressed a lot of misconceptions about how we study the past. We're used to the idea that we learn of ancient societies by examining artifacts and excavated ruins. But this really only works if you're going back a few thousand years. When you want to go back millions of years, it's more complicated. For example, the Earth is about 4.5 billion years old. Complex life appeared 600 million years ago. Fine.

But the oldest surface land ever discovered is the Paran Plains in the Negev Desert in Israel. It's about 1.8 million years old. That's it. Every other piece of exposed land we've ever found is newer than that. So where'd all the land go?

If the oldest exposed land on Earth is less than 2 million years old, where'd all the land go? Well, a couple of places. Every day, most land is subjected to some degree of physical and chemical weathering. Chemical reactions between minerals, oxidation, and even water breaks the surface down into small fragments. Then erosion carries the fragments away, either by wind or water.

This process is constant, so the oldest land on the surface of the planet is less than 2 million years old. There's even more.

Earth's crust is made up of tectonic plates, basically floating on the Earth's mantle. Over time, these plates move and shift and bump into each other, sometimes violently. When this happens, the denser portions of crust are forced down into the mantle, while the lighter bits are forced up. And although it's extremely rare, sometimes this happens all at once.

This gives Earth a brand new layer of crust. And all the old crust, the entire surface, is pulled back into the mantle. Now, scientists used to believe this was a long, slow process. They estimated the cycle took about 2 billion years.

But by analyzing lava, we now have a more accurate number. It wasn't 2 billion years, it was 500 million years. Now the Earth has existed for 4.5 billion years, but the surface of our planet and everything on it has been completely erased and rebuilt nine times. If ancient civilizations existed before humans, they could be very hard to detect.

Discovering fossils is a lot more difficult than people think. Very specific conditions need to be present for fossilization. The organism needs hard body parts like bones, teeth, and shells. The remains need to be quickly covered and protected from scavenging and erosion. You need high pressure to promote mineralization and low oxygen to prevent decomposition. All this stuff almost never happens.

Dinosaurs roamed the Earth for 180 million years. Over this time, trillions of individual animals lived and died. Yet we only have a few thousand near complete fossils. It's estimated that over two and a half billion Tyrannosaurus rexes lived and died on the Earth. But fewer than 100 fossils have ever been found, and only one of them is even complete.

That means we've only discovered 0.0000004% of this species. Less than one-tenth of 1% of all living things ever will end up as fossils. Schmidt and Frank said that a species as short-lived as Homo sapiens might not be represented in the existing fossil record at all.

The current area of urbanization is less than 1% of the Earth's surface. So human artifacts like roads and cities and machines, even megastructures, would only last a few thousand years. And once they're gone, they're unlikely to ever be found.

Many different natural events decrease the odds of discovering fossils or ruins. Rising tides cause land to slip into the ocean. About 13,000 years ago, the water level was much, much lower than it is today. This time in history is called the Younger Dryas. It was the end of the last ice age. At this time, about 30% of the Earth was covered in ice.

Then, due to some catastrophic event, all the ice suddenly melted. This meltwater swept across the world, and it didn't do it gently. Tsunamis and waves a thousand feet high tore across the landscape.

When the water was unleashed, it raised the sea level 400 feet. This rise in sea level put a huge portion of formerly dry land underwater. The amount of square miles of now submerged land is bigger than China and Europe combined. That's a lot of land gone. Any settlements, ruins or history existing near the coasts are just gone. Hundreds of feet or thousands of feet underwater.

Sinkholes can open up and swallow everything above it. A fossil or artifact that falls into a sinkhole can go down as far as 2,000 feet into the earth. Then there's liquefaction, which is absolutely terrifying. When wet sandy soil is shaken by a sudden earthquake, water pressure increases and the sand separates. Anything on the surface sinks into the earth until the shaking stops. It's like quicksand, but miles and miles of it.

Schmidt and Frank conclude that direct evidence of civilization can only go back about 4 million years. Even if the entire human race were eliminated by nuclear war, the radioactive evidence would disappear eventually. Okay, so archaeology and geology aren't going to help us find a lost civilization. Are there other methods for detecting the existence of advanced intelligent life in the distant past? Turns out, there are.

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at Grammarly.com slash podcast. That's G-R-A-M-M-A-R-L-Y dot com slash podcast. Grammarly. Easier said, done. Civilization, at least defined by the authors of the Silurian Hypothesis, is where industrialization occurs on a global scale, as ours does. As we speak, industrialization is leaving clues of our existence that will be detectable by scientists a hundred million years in the future.

Eventually, our time on Earth will be crushed down to nothing more than a thin layer of rock sediment. In a sedimentary core, a layer of a few centimeters is deposited every thousand years. And in those centimeters, future paleontologists will find evidence of our geologic era, called the Anthropocene. For example, we grow so much food now that our use of fertilizer is actually redirecting the planet's nitrogen supply.

This nitrogen cycling is also changing its isotopic signature. This isotope will be detectable in the sediment.

Agriculture and deforestation increase soil erosion. That erosion washes into the sea and becomes part of the sediment. Human mining activities have increased the amounts of gold, lead, chromium, platinum, and other metals. These too will be visible in the sediment at greater rates than before. But the element that really tells the story of civilization is carbon. Humans conquer the planet by harnessing combustion. It's

It seems reasonable that intelligent life forms everywhere would do the same. When we burn the tissue of long-dead plants, fossil fuels, we change the ratio of isotopes in the atmosphere. This is called the Seuss effect. Now, carbon comes in 15 flavors, but the most common isotopes are carbon-12, carbon-13, and carbon-14. Carbon-12 is light carbon. This is the isotope preferred by plants and used during photosynthesis. Atmosphere

Animals that eat plants consume the plant's carbon-12. And animals that eat animals that eat plants consume their carbon-12, and so on. Volcanic emissions are carbon-13. But carbon-14 is radioactive and decays predictably over time. Fossil fuels have no carbon-14 at all. As we burn more fossil fuels, the levels of carbon-13 and 14 go down while the level of enriched carbon-12 goes up.

All this carbon in the atmosphere also causes the Earth to warm slightly. And when looking through sedimentary layers from millions of years ago, this is what we need to see to determine if there was an advanced civilization. We need to see a large but temporary spike in carbon and oxygen, a large but temporary spike in metals, and a large but temporary spike in global temperature. We find that, and we're onto something. Well, we're not.

We found that and it happened 56 million years ago.

About 56 billion years ago, there was a sudden global change of carbon and oxygen isotope levels. Now, this is called the Paleocene-Eocene Thermal Maximum, or PETM. And the PETM only lasted about 100,000 years. And that's nothing in geologic time. Now, remember, that's about as long as we've been here. And during this time, the Earth's temperature rose to about 14 degrees Celsius higher than today's temperatures.

This was warm. We're talking t-shirt weather at the North Pole warm. The ice caps were completely gone. So is the PETM evidence of an ancient civilization? Well, probably not. It took the PETM 5,000 years to reach the level of carbon in the atmosphere that we've done in only 300 years. But here's the thing about that carbon spike. Nobody knows what caused it.

The best guess is the PETM was caused by a massive volcanic eruption on the seafloor. This released methane hydrates, which increased the concentration of CO2 in the atmosphere to about a thousand parts per million. But that's just an educated guess. Nobody knows for sure.

What's weird though, is there is evidence of lots of fossil carbon in the atmosphere during that time. Like there were factories running and cars and planes. There was more CO2 in the atmosphere than we have now. And a few million years later, these conditions happened again. This event is called the Eocene Layers of Mysterious Origin. Yes, that's really the name and I love it.

And there were other massive events in the Cretaceous period that depleted the Earth's oceans of oxygen for thousands of years. Volcanic eruptions are probably what caused these events, but there's no way to know for sure.

Until we're able to see our own geological layer from an outside perspective, we really have nothing to compare it to. Someday, all evidence of our existence could look exactly like the PETM. Our CO2 is only about 400 parts per million, nowhere near the 1,000 parts per million of the PETM event. Still, 400 parts per million is high enough to leave a clue that we were here. But we're changing that.

Every day, advancements are made to fix and even reverse the amount of carbon in the atmosphere. In the U.S., 90% of electricity comes from coal. But as of 2020, the number is going down by a lot. Between 2019 and 2020, just one year, coal use dropped 30%.

The U.S. and other countries are switching to cleaner energy like natural gas instead of coal. That helps. But there is something else helping. Smart devices. Turns out these devices really are smart and are helping us save a lot of energy. Things like smart lights know to turn themselves off if you're not home. Smart thermostats do the same. We're creating these devices to make our lives easier. But this technology is also good for the planet. A win-win.

Meanwhile, plastics and styrofoams are being replaced with biodegradable material. Solar panel efficiency is going up year after year. Power grids as a whole are being replaced with smart grids to reduce wasted energy.

We're doing a lot to reduce our impact on the planet. And look, I'm not making a political statement about global warming or climate change or crisis or whatever it is. The earth is getting warmer. That's true. But whether this is a crisis, that's a debate. And if it is a crisis, is there anything we can do about it? That's also a debate. But whatever your politics, I think we can all agree that cleaner air and water is better. Now, I bring this up because all the things we're doing to clean up our environment is

That's also erasing evidence that we were here. And who's to say a previous advanced species didn't do all the same things we did? Maybe they had an industrial revolution too. They created pollution, then they cleaned it up, but they also erased the clues to show they were here.

We have reached the point where we've stopped making things that will last forever. We make things that only last their useful life. Then we recycle that stuff into new stuff. Even things like rubber tires, styrofoam, plastic. There's technology to address all those. As we speak, there are ships dragging giant nets through the ocean, and these nets pull tons and tons of trash out of the water every year.

Again, this is great, but we're getting rid of so many things that would eventually be part of our sediment layer. We may even get to the point that the entire sediment layer of our existence is completely gone as if we never happened. A missing sediment layer? That doesn't make sense, does it? That can't happen, can it? PenFed Free Checking offers zero fees and zero balance requirements for zero hassle. PenFed Access America Checking lets you earn money on your balance for dreams big and small.

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There is a huge geological mystery known as the Great Unconformity. Geologists travel back through time by looking at sediment layers. Each layer down represents further back in time. But once geologists get down to about 850 million years ago, it gets weird. A layer of sediment is missing. A few layers, actually, totaling about 1 billion years of missing time.

About 70 million years after the Great Unconformity, or GU, the planet went through a snowball event. This process, called glaciation, covered the Earth in glaciers. The entire surface of the Earth was frozen, even the oceans. Whatever caused the GU pulled massive amounts of carbon dioxide out of the atmosphere, setting up the conditions for glaciation. We know how the GU happened, but we don't know what caused it.

Scientists believe it could have been related to the ancient supercontinent Rodinia breaking up into smaller subcontinents. A supercontinent breaks up when an uplift event occurs. This exposes a lot more rock to weathering and erosion. A similar event happened about 225 million years ago.

This time it was Pangea breaking up. But here's the weird part. There are sediment layers from Pangea, but there wasn't another snowball event. There was no change in CO2 levels. During the entire life of the Earth, seven different supercontinents have formed and broken apart. But the great unconformity is completely unique because all that CO2 was removed from the atmosphere. And when you look at a sediment layer and see a massive removal of CO2, you know what that looks like?

It looks a lot like a civilization cleaning up after itself.

There are some discoveries that defy explanation. A civilization has a strict timeline for which technology progresses. You can't forge metals before you harness fire. You can't create the light bulb before you discover electricity. Yet some things don't always follow the timeline and we don't really know why. In 1996, an archaeologist discovered a cave. It had iron pipes running from inside it to a salty lake nearby.

Dating the pipes indicated they were forged at least 150,000 years ago, long before humans discovered fire. Their exact purpose is unknown, but one theory suggests they could have been part of a power plant. In a mine in Africa, physicists discovered uranium ore had gone through the process of nuclear fission.

But this uranium was mined from deep within the Earth. Uranium just doesn't go nuclear on its own. And not only that, chemical analysis of the ore indicated the fission happened nearly 2 billion years ago. Humans didn't build the power plant, and humans didn't cause the nuclear fission. So who did?

Deep below the Earth's crust, more than 40 miles down, is the mantle. The mantle makes up 84% of the Earth's volume. It's 1,800 miles thick. And it's hot down there. The temperature ranges from 1,000 degrees Celsius near the crust to as high as 3,700 degrees near the core.

And as you go deeper into the mantle, the pressure increases, reaching as high as 1.3 million times atmospheric pressure. Even though it's right below our feet, the mantle is a strange and foreign world. In the intense heat and pressure, atoms start behaving differently. Rock becomes flexible, and oxygen acts more like metal than gas.

more than a quadrillion tons of diamonds can be found down there. There could be minerals that we can't even imagine because they're not found on the surface. Among the diamonds and minerals are two massive objects known as Large Low Shear Velocity Provinces, or LLVPs.

LLVP isn't a very descriptive title, so scientists also call them the blobs. And they stretch for thousands of miles and are taller than 200 Mount Everest's stacked on top of each other. These are two absolutely massive structures reaching up from the Earth's core toward the surface.

The shapes of the LLVPs are also very strange. They're not a single round mass of material, but multiple cavernous layers of blob. These caverns are connected in some parts by massive tunnels. If one were to keep an open mind, they would almost look like underground cities.

If there was once a civilization living on Earth millions of years ago, who's to say they didn't make the LLVPs? They could have built great cities made of materials they created, able to withstand even the pressure of the mantle. But they couldn't have predicted the way the crust would shift and the tectonic plates broke apart. Then their cities were destroyed and their civilization ended. Or maybe it didn't.

In the future, humans will be able to travel the solar system with ease. We'll even be able to visit nearby stars. It will be a long trip, but we'll be able to get there with only minor difficulties. But the vast majority of the universe will likely always be beyond our grasp. Space is just too big, and there's too much of it between galaxies.

Even if there is a civilization out there, it's so far away, visiting Earth would be a challenge, if not impossible. But UFOs do exist. People see them all the time. It's clearly advanced technology. What if all this activity is not from extraterrestrials from another planet, but from superterrestrials from our planet? ♪

That's the theory, and the theory is that it's actually their planet, not ours. Superterrestrials developed on Earth as an intelligent species long before humans, and at a certain point, whether to escape an ice age or planetary cataclysm, they decided to go underground.

And there's been a lot of UFO activity seen around nuclear weapons facilities. They're interfering with tests and neutralizing weapons. Now, this would make sense if another more advanced species was living on this planet and if they felt it was their planet.

They never destroy the nuclear facilities, so it's really not an act of aggression, but more of a, hey, keep it down up here. We'll let you live on our planet, but, you know, keep it nice. Because the Earth is always changing, anything that was once on the surface eventually ends up beneath it. The likelihood of finding much evidence on the land is pretty slim. But we could find it in the sky.

If an ancient species reached our level of technology, you'd expect them to launch satellites. If their technology exceeded ours, they might still have satellites. Most of the objects we put into space don't last very long. A few years, even decades, but that's about it. At some point, we stop servicing old satellites. They get shot into space, they crash into the ocean or just burn up in the atmosphere. But someday we'll get to the point where satellites could last a long time.

maybe even thousands of years. And when this happens, we'll probably put them in geostationary orbit. This higher orbit is about 22,000 miles above the surface. At this height, an object could orbit the Earth forever. As long as nothing bumped into it, it would just keep going and going. In 1954, the Air Force reported something strange.

two satellites were orbiting the Earth. The problem was, satellites hadn't been invented yet. And this object is still there. It's been seen, heard, even photographed. Nikola Tesla received transmissions from it in 1899. Tesla's signals were analyzed in 1973. The data indicated this object was orbiting the Earth during the Stone Age and possibly even longer.

It's called the Black Knight satellite. And I've covered the Black Knight in detail before. And there's good reason to be skeptical. But there's something else in orbit that could be evidence of an advanced civilization. Because there's something very wrong with the moon.

The Moon has been around since before recorded history, but its existence still can't really be explained by scientists. They can't tell us how it formed, they don't have an answer for its unusual orbit, and they don't know why it's so close to Earth. The Moon's density, composition, and structure are all mysteries to science, and the more we learn about the Moon, the more problems we find. There are scientific models that solve some of these problems, but not all.

Only one theory explains every problem with the moon, that the moon is artificial, it's hollow, and was put into its orbit around Earth by someone. I have an entire episode on the hollow moon theory, and to be honest, when I first heard the theory, I thought it was absolutely bonkers. And after a little research, I started thinking, okay, the moon is kind of weird. But by the time my research was finished, I was fully moon-pilled. The moon is wrong, it's weird, and it shouldn't be there.

So if someone put it there, were they from Earth or from somewhere else? Is the moon actually evidence of an earlier civilization? Well, to be honest, most scientists believe that we are the first civilization. But they do admit that if an advanced species only existed for as long as we have, they would be really hard to detect.

Even the authors of the Silurian Hypothesis admit, if you're not specifically looking at the right time in history and for the right details, you probably miss it. But the Silurian Hypothesis does give us an interesting set of tools. Tools that might not help us find ancient civilizations on our planet, but could help us find them on other planets.

The Drake equation is a well-known formula for estimating the number of advanced civilizations in our galaxy. It boils down to this. Take the number of stars that have planets, take the fraction of those that have the conditions to support life, then take the fraction of those planets that develop life, and finally the fraction of those that can develop intelligent life.

This number fluctuates as new discoveries are made, but still, the number of civilizations out there could be anywhere from 150,000 to 1.5 billion.

What's interesting is, now that we have the Silurian hypothesis, any planet that can develop intelligent life can maybe develop it again and again over millions or billions of years. And this was the original premise of Frank and Schmidt's paper. Yes, they wondered about life on other planets in the galaxy, but they also considered civilizations that may have existed right here in our own solar system.

There was a time when Mars was much warmer and had giant oceans of water. There was a time when the conditions on Venus could have supported life. One of Jupiter's moons, Europa, is covered by a saltwater ocean.

When we finally get core samples from these planets, we may realize that though civilizations don't exist there now, the distant past could tell a very different story. Our species hasn't been here very long, and we're in the process of cleaning up the evidence of our impact on the planet. But what about human fossils? There's a lot of people. Surely there will be a lot of fossils of us.

Probably not. The way we care for the dead makes fossilization almost impossible. Being buried in the ground, at sea, or cremated means that long-lasting remains are highly unlikely. There are 8.1 billion people on the Earth right now, each with about 206 bones. Of our more than 1.7 trillion bones, it's estimated only 60 will be fossilized. Not

Not 60 million, not 60,000, just 60 out of 1.7 trillion. Sure, we've found fossils of humans already, but how old are they? 10,000 years? 100,000? The odds of anything being left in millions of years is actually pretty low.

Now, we've talked about a lot of pretty wild theories today, and it's healthy to be skeptical, but it's just as important to keep an open mind. Sometimes the ridiculous theory is going to be right. It's already happened time and time again. And the authors of the Silurian hypothesis don't believe there were ancient civilizations on Earth before humans. And our civilization may be unique in the universe.

But they do lay out an exciting possibility that there could be millions of civilizations out there. And now we have the tools to find them.

Thank you so much for hanging out with me today. My name is AJ. This has been the Y-Files. If you had fun or learn anything, do me a favor, leave the podcast a nice review. That lets me know to keep making these things for you. And like most topics I cover on the Y-Files, today's was recommended by you. So if there's a story you'd like to learn more about, go to the Y-Files.com slash tips.

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