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We think we’re the first advanced earthlings—but how do we really know?

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Imagine if, many millions of years ago, dinosaurs drove cars through cities of mile-high buildings. A preposterous idea, right? Over the course of tens of millions of years, however, all of the direct evidence of a civilization—its artifacts and remains—gets ground to dust. How do we really know, then, that there weren’t previous industrial civilizations on Earth that rose and fell long before human beings appeared?

It’s a compelling thought experiment, and one that Adam Frank, a professor of physics and astronomy at the University of Rochester, and Gavin Schmidt, the director of the NASA Goddard Institute for Space Studies, take up in a paper published in the International Journal of Astrobiology .

“Gavin and I have not seen any evidence of another industrial civilization,” Frank explains. But by looking at the deep past in the right way, a new set of questions about civilizations and the planet appear: What geological footprints do civilizations leave? Is it possible to detect an industrial civilization in the geological record once it disappears from the face of its host planet? “These questions make us think about the future and the past in a much different way, including how any planetary-scale civilization might rise and fall.”

In what they deem the “Silurian Hypothesis,” Frank and Schmidt define a civilization by its energy use. Human beings are just entering a new geological era that many researchers refer to as the Anthropocene, the period in which human activity strongly influences the climate and environment. In the Anthropocene, fossil fuels have become central to the geological footprint humans will leave behind on Earth. By looking at the Anthropocene’s imprint, Schmidt and Frank examine what kinds of clues future scientists might detect to determine that human beings existed. In doing so, they also lay out evidence of what might be left behind if industrial civilizations like ours existed millions of years in the past.

Human beings began burning fossil fuels more than 300 years ago, marking the beginnings of industrialization. The researchers note that the emission of fossil fuels into the atmosphere has already changed the carbon cycle in a way that is recorded in carbon isotope records. Other ways human beings might leave behind a geological footprint include:

• Global warming, from the release of carbon dioxide and perturbations to the nitrogen cycle from fertilizers
• Agriculture, through greatly increased erosion and sedimentation rates
• Plastics, synthetic pollutants, and even things such as steroids, which will be geochemically detectable for millions, and perhaps even billions, of years
• Nuclear war, if it happened, which would leave behind unusual radioactive isotopes

Light of the Stars Read more about Professor Frank’s latest book and other work

“As an industrial civilization, we’re driving changes in the isotopic abundances because we’re burning carbon,” Frank says. “But burning fossil fuels may actually shut us down as a civilization. What imprints would this or other kinds of industrial activity from a long dead civilization leave over tens of millions of years?”

The questions raised by Frank and Schmidt are part of a broader effort to address climate change from an astrobiological perspective, and a new way of thinking about life and civilizations across the universe. Looking at the rise and fall of civilizations in terms of their planetary impacts can also affect how researchers approach future explorations of other planets.

“We know early Mars and, perhaps, early Venus were more habitable than they are now, and conceivably we will one day drill through the geological sediments there, too,” Schmidt says. “This helps us think about what we should be looking for.”

Schmidt points to an irony, however: if a civilization is able to find a more sustainable way to produce energy without harming its host planet, it will leave behind less evidence that it was there.

“You want to have a nice, large-scale civilization that does wonderful things but that doesn’t push the planet into domains that are dangerous for itself, the civilization,” Frank says. “We need to figure out a way of producing and using energy that doesn’t put us at risk.”

That said, the earth will be just fine, Frank says. It’s more a question of whether humans will be.

Can we create a version of civilization that doesn’t push the earth into a domain that’s dangerous for us as a species?

“The point is not to ‘save the earth,’” says Frank. “No matter what we do to the planet, we’re just creating niches for the next cycle of evolution. But, if we continue on this trajectory of using fossil fuels and ignoring the climate change it drives, we human beings may not be part of Earth’s ongoing evolution.”

The Silurian Hypothesis: A nod to Doctor Who

Adam Frank and Gavin Schmidt call their study the Silurian Hypothesis after a race of intelligent, bipedal reptiles—known as the Silurians—introduced in a 1970 episode of the British science fiction series Doctor Who . The Silurians supposedly evolved on Earth during the eponymous era, a geological time period lasting from 443 million to 416 million years ago. To avoid any kind of catastrophe, the reptiles went into hibernation for millions of years before being awakened by secret nuclear experiments in a Welsh mine.

“When we were writing this paper,” Schmidt says, “I tried to find examples of terrestrial, non-human civilizations in the science-fiction literature, but I wasn’t able to find anything earlier than the 1970s. Despite it being exceedingly unlikely that there were any civilizations in the Silurian period—this was before the land plants and animals had really established themselves—it seemed fitting to name our idea after the first example that people thought about, even if this is fiction.”

Astrophysicist Adam Frank

A self-described “evangelist of science,” Frank regularly writes   and speaks about subjects like intelligent life forms in the universe, high-energy-density physics, space exploration and missions, climate change, and more.

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Was There a Civilization on Earth Before Humans?

A look at the available evidence

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It only took five minutes for Gavin Schmidt to out-speculate me.

Schmidt is the director of NASA ’s Goddard Institute for Space Studies (a.k.a. GISS), a world-class climate-science facility. One day last year, I came to GISS with a far-out proposal. In my work as an astrophysicist, I’d begun researching global warming from an “astrobiological perspective.” That meant asking whether any industrial civilization that rises on any planet will, through its own activity, trigger its own version of a climate shift. I was visiting GISS that day hoping to gain some climate-science insights and, perhaps, collaborators. That’s how I ended up in Gavin’s office.

Just as I was revving up my pitch, Gavin stopped me in my tracks.

“Wait a second,” he said. “How do you know we’re the only time there’s been a civilization on our own planet?”

It took me a few seconds to pick up my jaw off the floor. I had certainly come into Gavin’s office prepared for eye rolls at the mention of “ exo-civilizations .” But the civilizations he was asking about would have existed many millions of years ago. Sitting there, seeing Earth’s vast evolutionary past telescope before my mind’s eye, I felt a kind of temporal vertigo. “Yeah,” I stammered. “Could we tell if there’d been an industrial civilization that deep in time?”

We never got back to aliens. Instead, that first conversation launched a new study we’ve recently published in the International Journal of Astrobiology . Though neither of us could see it at that moment, Gavin’s penetrating question opened a window not just onto Earth’s past, but also onto our own future.

We’re used to imagining extinct civilizations in terms of sunken statues and subterranean ruins. These kinds of artifacts of previous societies are fine if you’re only interested in timescales of a few thousands of years. But once you roll the clock back to tens of millions or hundreds of millions of years, things get more complicated.

When it comes to direct evidence of an industrial civilization—things like cities, factories, and roads—the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. It’s “just” 1.8 million years old—older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. Go back much further than the Quaternary, and everything has been turned over and crushed to dust.

And, if we’re going back this far, we’re not talking about human civilizations anymore. Homo sapiens didn’t make their appearance on the planet until just 300,000 years or so ago . That means the question shifts to other species, which is why Gavin called the idea the Silurian hypothesis, after an old Doctor Who episode with intelligent reptiles.

So could researchers find clear evidence that an ancient species built a relatively short-lived industrial civilization long before our own? Perhaps, for example, some early mammal rose briefly to civilization building during the Paleocene epoch, about 60 million years ago. There are fossils, of course. But the fraction of life that gets fossilized is always minuscule and varies a lot depending on time and habitat. It would be easy, therefore, to miss an industrial civilization that lasted only 100,000 years—which would be 500 times longer than our industrial civilization has made it so far.

Given that all direct evidence would be long gone after many millions of years, what kinds of evidence might then still exist? The best way to answer this question is to figure out what evidence we’d leave behind if human civilization collapsed at its current stage of development.

Now that our industrial civilization has truly gone global, humanity’s collective activity is laying down a variety of traces that will be detectable by scientists 100 million years in the future. The extensive use of fertilizer , for example, keeps 7 billion people fed, but it also means we’re redirecting the planet’s flows of nitrogen into food production. Future researchers should see this in characteristics of nitrogen showing up in sediments from our era. Likewise our relentless hunger for the rare-Earth elements used in electronic gizmos. Far more of these atoms are now wandering around the planet’s surface because of us than would otherwise be the case. They might also show up in future sediments, too. Even our creation, and use, of synthetic steroids has now become so pervasive that it too may be detectable in geologic strata 10 million years from now.

And then there’s all that plastic. Studies have shown that increasing amounts of plastic “ marine litter ” are being deposited on the seafloor everywhere from coastal areas to deep basins, and even in the Arctic. Wind, sun, and waves grind down large-scale plastic artifacts, leaving the seas full of microscopic plastic particles that will eventually rain down on the ocean floor, creating a layer that could persist for geological timescales.

The big question is how long any of these traces of our civilization will last. In our study, we found that each had the possibility of making it into future sediments. Ironically, however, the most promising marker of humanity’s presence as an advanced civilization is a by-product of one activity that may threaten it most.

When we burn fossil fuels , we’re releasing carbon back into the atmosphere that was once part of living tissues. This ancient carbon is depleted in one of that element’s three naturally occurring varieties, or isotopes. The more fossil fuels we burn, the more the balance of these carbon isotopes shifts. Atmospheric scientists call this shift the Suess effect, and the change in isotopic ratios of carbon due to fossil-fuel use is easy to see over the past century. Increases in temperature also leave isotopic signals. These shifts should be apparent to any future scientist who chemically analyzes exposed layers of rock from our era. Along with these spikes, this Anthropocene layer might also hold brief peaks in nitrogen, plastic nanoparticles, and even synthetic steroids. So if these are traces our civilization is bound to leave for the future, might the same “signals” exist right now in rocks just waiting to tell us of civilizations long gone?

Fifty-six million years ago, Earth passed through the Paleocene-Eocene Thermal Maximum (PETM). During the PETM, the planet’s average temperature climbed as high as 15 degrees Fahrenheit above what we experience today. It was a world almost without ice, as typical summer temperatures at the poles reached close to a balmy 70 degrees Fahrenheit. Looking at the isotopic record from the PETM, scientists see both carbon and oxygen isotope ratios spiking in exactly the way we expect to see in the Anthropocene record. There are also other events like the PETM in Earth’s history that show traces like our hypothetical Anthropocene signal. These include an event a few million years after the PETM dubbed the Eocene Layers of Mysterious Origin, and massive events in the Cretaceous that left the ocean without oxygen for many millennia (or even longer).

Are these events indications of previous nonhuman industrial civilizations? Almost certainly not. While there is evidence that the PETM may have been driven by a massive release of buried fossil carbon into the air, it’s the timescale of these changes that matter. The PETM’s isotope spikes rise and fall over a few hundred thousand years. But what makes the Anthropocene so remarkable in terms of Earth’s history is the speed at which we’re dumping fossil carbon into the atmosphere. There have been geological periods where Earth’s CO 2 has been as high or higher than it is today, but never before in the planet’s multibillion-year history has so much buried carbon been dumped back into the atmosphere so quickly. So the isotopic spikes we do see in the geologic record may not be spiky enough to fit the Silurian hypothesis’s bill.

But there is a conundrum here. If an earlier species’s industrial activity is short-lived, we might not be able to easily see it. The PETM’s spikes mostly show us Earth’s timescales for responding to whatever caused it, not necessarily the timescale of the cause. So it might take both dedicated and novel detection methods to find evidence of a truly short-lived event in ancient sediments. In other words, if you’re not explicitly looking for it, you might not see it. That recognition was, perhaps, the most concrete conclusion of our study.

It’s not often that you write a paper proposing a hypothesis that you don’t support. Gavin and I don’t believe the Earth once hosted a 50-million-year-old Paleocene civilization. But by asking if we could “see” truly ancient industrial civilizations, we were forced to ask about the generic kinds of impacts any civilization might have on a planet. That’s exactly what the astrobiological perspective on climate change is all about. Civilization building means harvesting energy from the planet to do work (i.e., the work of civilization building). Once the civilization reaches truly planetary scales, there has to be some feedback on the coupled planetary systems that gave it life (air, water, rock). This will be particularly true for young civilizations like ours still climbing up the ladder of technological capacity. There is, in other words, no free lunch. While some energy sources will have lower impact—say solar versus fossil fuels—you can’t power a global civilization without some degree of impact on the planet.

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Once you realize, through climate change, the need to find lower-impact energy sources, the less impact you will leave. So the more sustainable your civilization becomes, the smaller the signal you’ll leave for future generations.

In addition, our work also opened up the speculative possibility that some planets might have fossil-fuel-driven cycles of civilization building and collapse. If a civilization uses fossil fuels, the climate change they trigger can lead to a large decrease in ocean oxygen levels. These low oxygen levels (called ocean anoxia) help trigger the conditions needed for making fossil fuels like oil and coal in the first place. In this way, a civilization and its demise might sow the seed for new civilizations in the future.

By asking about civilizations lost in deep time, we’re also asking about the possibility for universal rules guiding the evolution of all biospheres in all their creative potential, including the emergence of civilizations. Even without pickup-driving Paleocenians, we’re only now learning to see how rich that potential might be.

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The Silurian Hypothesis

*We may not be the first Anthropocene.

And if so, how would we even know

Today we get an answer thanks to Gavin Schmidt at the NASA Goddard Institute for Space Studies in New York city and Adam Frank at the University of Rochester. These guys have a name for the idea that an industrial civilization may have predated humanity: the Silurian hypothesis. They study the signature that our own civilization is likely to leave behind and ask whether it will be detectable millions of years from now. Their conclusion is that our probable impact on the planet will be palpable but in some ways hard to distinguish from various other events in the geological record.

Their work has some interesting implications for how we should study Earth and the impact we have on it. The research should also help astrobiologists decide what to look for elsewhere in the universe.

Schmidt and Frank begin by setting out just how little we know about ancient Earth. The oldest part of Earth’s surface is the Negev Desert in southern Israel, which is 1.8 million years old. Older surfaces exist only in exposed areas or as a result of mining and drilling operations. Given these constraints, the evidence of activity by Homo sapiens stretches back some 2.5 million years — not really that far in geological terms. The ocean floor is relatively young too, because ocean crust is constantly recycled. As a result, all ocean sediment post-dates the Jurassic Period and is therefore less than 170 million years old.

In any case, say Schmidt and Frank, the fraction of life that gets fossilized is tiny. Dinosaurs roamed Earth for some 180 million years, and yet only a few thousand near-complete specimens exist. Modern humans have existed for just a few tens of thousands of years. “Species as short-lived as homo sapiens (so far) might not be represented in the existing fossil record at all,” say Schmidt and Frank.

What of human artifacts — roads, buildings, baked-bean tins, and silicon chips? These, too, are unlikely to survive long, or to be found even if they do. “The current area of urbanization is less than 1% of the Earth’s surface,” point out the researchers.

“We conclude that for potential civilizations older than about 4 million years, the chances of finding direct evidence of their existence via objects or fossilized examples of their population is small,” they say. But there is another type of evidence: our civilization also leaves a chemical footprint....

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If a technologically advanced species existed on Earth before us, they may have left a trace.

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If an advanced species lived on Earth before us, would we know?

Image Credit: Liu zishan/Shutterstock.com

In Doctor Who,  an alien species called the Silurians exists – technologically-advanced humanoid reptiles who lived long before humans, going into hiding and being basically undiscovered again until everyone's favorite time-traveling alien came along in his phone box. So far, so not science. However, in 2018 two University of Cambridge scientists named their paper – The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record? – after the fictional species.

Published in the Journal of Astrobiology, the paper does not argue that there was a technologically-advanced species long before humanity, but proposed the interesting hypothetical question of whether it would be possible to find "geological fingerprints" of a bygone civilization that expired millions of years ago.

"One of the key questions in assessing the likelihood of finding such a civilization is an understanding of how often, given that life has arisen and that some species are intelligent, does an industrial civilization develop?" they  write in the paper . 

"Humans are the only example we know of, and our industrial civilization has lasted (so far) roughly 300 years (since, for example, the beginning of mass production methods). This is a small fraction of the time we have existed as a species, and a tiny fraction of the time that complex life has existed on the Earth's land surface."

"This short time period raises the obvious question as to whether this could have happened before."

As well as being an interesting hypothesis to ponder, seeking to answer the question could also help us search for signs of advanced civilizations on exoplanets. As the paper points out, humans have left notable marks on the planet that will certainly last for many years in our (relatively short) time altering the planet's climate and ecosystems. However, that doesn't mean that these changes will be detectable millions of years from now. In fact, the record we leave – for instance, in the sediment – may only be a few centimeters thick. This may be true even if we survive for much longer than our current age.

"The longer human civilization lasts, the larger the signal one would expect in the record," the team write. "However, the longer a civilization lasts, the more sustainable its practices would need to have become in order to survive. The more sustainable a society (e.g. in energy generation, manufacturing or agriculture) the smaller the footprint on the rest of the planet. But the smaller the footprint, the less of a signal will be embedded in the geological record."

The team discuss other markers we could leave for a species millions of years from now (or that may have been left for us). Some will be indistinguishable from naturally occurring phenomena such as the Cretaceous and Jurassic ocean anoxic events – but others would be clear signs that we were here, and we absolutely trashed the place.

"We speculate that some specific tracers that would be unique, specifically persistent synthetic molecules, plastics and (potentially) very long-lived radioactive fallout in the event of nuclear catastrophe," the team write. 

"Absent those markers, the uniqueness of the event may well be seen in the multitude of relatively independent fingerprints as opposed to a coherent set of changes associated with a single geophysical cause."

The team does not give a definitive answer in the paper, but suggest that if there were other ancient advanced species to be found, they would be discovered through exploration of elemental and compositional anomalies in the sediment record.

"While we strongly doubt that any previous industrial civilization existed before our own, asking the question in a formal way that articulates explicitly what evidence for such a civilization might look like raises its own useful questions related both to astrobiology and to Anthropocene studies," they conclude. 

"We hope that this paper will serve as motivation to improve the constraints on the hypothesis so that in future we may be better placed to answer our title question."

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Schmidt, G.A. , and A. Frank, 2019: The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record? Int. J. Astrobiol. , 18 , 142-150, doi:10.1017/S1473550418000095.

If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event.

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April 23, 2018

Could an Industrial Prehuman Civilization Have Existed on Earth before Ours?

A provocative new paper suggests some ways to find out

By Steven Ashley

How could we really know if industrial civilizations existed on Earth long before human beings appeared? That is the question posed in a scientific thought experiment by climate scientist Gavin Schmidt and astrophysicist Adam Frank.

Michael Osadciw University of Rochester

One of the creepier conclusions drawn by scientists studying the Anthropocene—the proposed epoch of Earth’s geologic history in which humankind’s activities dominate the globe—is how closely today’s industrially induced climate change resembles conditions seen in past periods of rapid temperature rise.

“These ‘hyperthermals,’ the thermal-maximum events of prehistory, are the genesis of this research,” says Gavin Schmidt, climate modeler and director of the NASA Goddard Institute for Space Studies. “Whether the warming was caused by humans or by natural forces, the fingerprints—the chemical signals and tracers that give evidence of what happened then—look very similar.”

The canonical example of a hyperthermal is the Paleocene-Eocene Thermal Maximum (PETM), a 200,000-year period that occurred some 55.5 million years ago when global average temperatures rose by five to eight degrees Celsius (nine to 14 degrees Fahrenheit). Schmidt has pondered the PETM for his entire career, and it was on his mind one day in 2017 when University of Rochester astrophysicist Adam Frank paid him a visit.

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Frank came to his office to discuss the idea of studying global warming from an “astrobiological perspective”—that is, investigating whether the rise of an alien industrial civilization on an exoplanet might necessarily trigger climate changes similar to those we see during Earth’s own Anthropocene. But almost before Frank could describe how one might search for the climatic effects of industrial “exocivilizations” on newly discovered planets, Schmidt caught him up short with a surprising question: “How do you know we’re the only time there’s been a civilization on our own planet?“

Frank considered a moment before responding with a question of his own: “Could we even tell if there had been an industrial civilization [long before this one]?“

Their subsequent attempt to address both questions yielded a provocative paper on the possibility that Earth might have spawned more than one technological society during its 4.5-billion-year history. And if indeed some such culture arose on Earth in the murky depths of geologic time, how might scientists today discern signs of that incredible development? Or, as they put it in the paper: “If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today?“

Schmidt and Frank began by forecasting the geologic fingerprints the Anthropocene is likely to leave behind—such as hints of soaring temperatures and rising seas laid down in beds of sedimentary rock. These features, they noted, are very similar to the geologic leftovers of the PETM and other hyperthermal events. They then considered what tests could plausibly distinguish an industrial cause from otherwise naturally occurring climate changes. “These issues have never really been addressed to any great extent,” Schmidt notes. And that goes not only for scientists but evidently for science-fiction writers as well, he adds: “I looked back into the science-fiction literature to try to find the earliest example of a story featuring a nonhuman industrial civilization on Earth. The earliest I could find was in a Doctor Who episode.“

That 1970 episode of the classic TV series involves the present-day discovery of “Silurians”—an ancient race of technologically advanced, reptilian humanoids who predated the arrival of humans by hundreds of millions of years. According to the plot, these highly civilized saurians flourished for centuries until Earth’s atmosphere entered a period of cataclysmic upheaval that forced Homo reptilia to go into hibernation underground to wait out the danger. Schmidt and Frank paid tribute to the episode in the title of their paper: “The Silurian Hypothesis.”

Lost in Strata

Any plausibility of the Silurian hypothesis stems chiefly from the vast incompleteness of the geologic record, which only gets sparser the further back in time you go.

Today less than 3 percent of Earth’s surface is urbanized, and the chance that any of our great cities would remain over tens of millions of years is vanishingly low, says geologist Jan Zalasiewicz of the University of Leicester in England. A metropolis’s ultimate fate, he notes, mostly depends on whether the surrounding surface is subsiding (to be locked in rock) or rising (to be eroded away by rain and wind). “New Orleans is sinking; San Francisco is rising,” he says. The French Quarter, it seems, has much better chances of entering the geologic record than Haight-Ashbury.

“To estimate the odds of finding artifacts,” Schmidt says, “the back-of-the-envelope calculation for dinosaur fossils says that one fossil emerges every 10,000 years.” Dinosaur footprints are rarer still.

“After a couple of million years,” Frank says, “the chances are that any physical reminder of your civilization has vanished, so you have to search for things like sedimentary anomalies or isotopic ratios that look off.” The shadows of many prehuman civilizations could, in principle, lurk hidden in such subtleties.

But exactly what we would look for depends to some degree on how an Earthly but alien technological culture would choose to behave. Schmidt and Frank decided the safest assumption to make would be that any industrial civilization now or hundreds of millions of years ago should be hungry for energy. That means any ancient industrial society would have developed the capacity to widely exploit fossil fuels and other power sources, just as we did. “We’d be looking for globalized effects that would leave a worldwide trace”—planetary-scale physical-chemical tracers of energy-intensive industrial processes and their wastes, Schmidt says.

Next comes the issue of longevity—the longer a civilization’s energy-intensive period persists and the more its demands increase, the more obvious its presence should become in the geologic record. Consider our own industrial age, which has existed for only about 300 years out of a multimillion-year history of humanity. Now compare that minuscule slice of time with the half a billion years or so that creatures have lived on land. Humanity’s present rapacious phase of fossil-fuel use and environmental degradation, Frank says, is unsustainable for long periods. In time, it will diminish either by human choice or by the force of nature, making the Anthropocene less of an enduring era and more of a blip in the geologic record. “Maybe [civilizations like ours] have happened multiple times, but if they each only last 300 years, no one would ever see them,” Frank says.

Taking all this into consideration, what remains is a menu of diffuse long-lived tracers including fossil-fuel combustion residues (carbon, primarily), evidence of mass extinctions, plastic pollutants, synthetic chemical compounds not found in nature and even transuranic isotopes from nuclear fission. In other words, what we would need to look for in the geologic record are the same distinctive signals that humans are laying down right now.

Signs of Civilization

Finding signs of an altered carbon cycle would be one big clue to previous industrial periods, Schmidt says. “Since the mid-18th century, humans have released half a trillion tons of fossil carbon at high rates. Such changes are detectable in changes in the carbon isotope ratio between biological and inorganic carbon—that is, between the carbon incorporated into things like seashells and that which goes instead into lifeless volcanic rock.”

Another tracer would be distinctive patterns of sediment deposition. Large coastal deltas would hint at boosted levels of erosion and rivers (or engineered canals) swollen from increased rainfall. Telltale traces of nitrogen in the sediments could suggest the widespread use of fertilizer, fingering industrial-scale agriculture as a possible culprit; spikes in metal levels in the sediments might instead point to runoff from manufacturing and other heavy industry.

More unique, specific tracers would be nonnaturally occurring, stable synthetic molecules such as steroids and many plastics, along with well-known pollutants, including polychlorinated biphenyls (toxic chemical compounds from electrical devices) and chlorofluorocarbons (ozone-eating molecules from refrigerators and aerosol sprays).

The key strategy in distinguishing the presence of industry from nature, Schmidt notes, is developing a multifactor signature. Absent artifacts or convincingly clear markers, the uniqueness of an event may well be seen in many relatively independent fingerprints as opposed to the coherent set of changes that are seen to be associated with a single geophysical cause.

“I find it amazing that no one had worked all this out before, and I’m really glad that somebody has taken a closer look at it,” says Pennsylvania State University astronomer Jason Wright, who in 2017 published “a fluffy little paper” exploring the counterintuitive notion that the best place to find evidence of any of Earth’s putative prehuman civilizations may well be off-world. If, for instance, dinosaurs built interplanetary rockets, presumably some remnants of that activity might remain preserved in stable orbits or on the surfaces of more geologically inert celestial bodies such as the moon.

“Look, 200 years ago the question of whether there might be a civilization on Mars was a legitimate one,” Wright says. “But once the pictures came out from interplanetary probes, that was settled for good. And that view became ingrained, so now it’s not a valid topic for scientific inquiry; it’s considered ridiculous. But no one’s ever put the actual scientific limits on it—on what may have happened a long time ago.”

Wright also acknowledges the potential for this work to be misinterpreted. “Of course, no matter what, this is going to be interpreted as ‘Astronomers Say Silurians Might Have Existed,’ even though the premise of this work is that there is no such evidence,” he says. “Then again, absence of evidence is not evidence of absence.”

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Title: the silurian hypothesis: would it be possible to detect an industrial civilization in the geological record.

Abstract: If an industrial civilization had existed on Earth many millions of years prior to our own era, what traces would it have left and would they be detectable today? We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event.

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The ‘Silurian Hypothesis’ Debate: Could Earth Have Once Harbored a Pre-Human Industrial Civilization?

It might seem like something from Ancient Aliens , but it’s an important thought experiment.

• The astrobiologists who developed the thought experiment concluded that there is not strong evidence in Earth’s geologic record to support such a claim.
• However, we still lack the scientific methods that would allow us to dive deep into Earth’s behaviors over such a long time span, so we may want to keep an open mind.

Complex life on our planet has existed for at least 400 million years . Yet as a species, we only managed to create an industrial civilization around 300 years ago. But, what if an earlier industrial civilization existed on Earth millions of years ago? If that were so, how would we be able to prove it—or disprove it? This is the crux of the Silurian hypothesis, a fascinating thought experiment that appeared in a study published in 2018 in the International Journal of Astrobiology .

The possibility of life elsewhere in the universe and its parallels with the Anthropocene — the current geological epoch, during which humans have impacted Earth to the point of no return—has long puzzled Adam Frank , Ph.D., a professor of astrophysics at the University of Rochester, New York, and one of the two authors of the study.

“Is it common for any civilization that reaches our level of energy use to trigger their own version of climate change? I was wondering. If there are alien civilizations , would they also trigger climate change?” Frank ponders. With this whirlwind of thoughts in mind, Frank visited the NASA Goddard Institute of Space Sciences (GISS), an elite climate-science facility at the University of Columbia, New York. He wanted to share his thoughts with climate researchers, and surely expected lots of raised eyebrows and skeptical stares in the process.

“I went into the meeting with Gavin A. Schmidt [a climatologist and the director of NASA GISS with a Ph.D. in applied mathematics], and started talking about aliens. And then Gavin stopped me and said, ‘Wait a second. How do you know we’re the only time there’s been a civilization on our own planet?’’’ Frank tells Popular Mechanics . The question was an “Aha!” moment for Frank, mostly because it allowed him to consider revisiting facts he had taken for granted.

Evidence in Earth’s Geologic Record

Homo sapiens first appeared on Earth about 300,000 years ago . In the unlikely case that such an old industrial civilization had existed, it would predate the species to which we all belong. It was then that Schmidt called the idea the Silurian hypothesis, paying homage to the sophisticated reptilian humanoids awoken by nuclear testing after 400 million years of hibernation in a 1970s episode of the British science fiction television series Doctor Who. The study authors decided to laser in on the time period from 4 million years ago to 400 million years ago.

But going back hundreds of millions of years to find traces of a potential pre- Homo Sapiens civilization is not a piece of cake.

“After a few million years, Earth is pretty much resurfaced. You’re not going to have any statues , buildings , or anything left,” Frank says. Fossil records will be virtually nonexistent as everything will have crumbled to dust. The only evidence would come in the form of chemical imprints. “You’d have to look at each layer of rock, and then try and detect trends—look for changes in things like the carbon or oxygen isotopes, which are tracers of things like carbon dioxide. An industrial civilization would dump lots of carbon dioxide into the atmosphere, just like we do,” Frank says. Plastic or nanoparticles would also be good indicators of an industrial civilization that occurred in time immemorial.

Schmidt and Frank were intrigued by the period of geological history known as the Paleocene-Eocene Thermal Maximum (PETM), because something peculiar happened on our planet during it, 56 million years ago: Earth’s average temperature soared to 15 degrees Fahrenheit above what we have today, and the world became a temperate and iceless place. They investigated the carbon and oxygen isotope ratios from the PETM and indeed saw spikes, but they also saw declines, and all of these over a few hundred thousand years, which is nowhere near the speed at which carbon is currently suffocating the atmosphere. Frank says the PETM’s chemical differences pointed to a long-term climate change .

They also reviewed other “abrupt events” throughout time that are visible in the geologic record, including ocean anoxic events—when an ocean becomes depleted of oxygen—and extinction events . Unsurprisingly, and perhaps slightly disappointingly, they were not indicative of an industrial civilization, either.

Applying Occam’s Razor

“The hypothesis that Earth may have harbored long-extinct industrial civilizations and that existence may be recorded in the geologic record associated with climate change signatures is fascinating, however, even the authors are not sold on the likelihood of it being true,” Stephen Holler, Ph.D., an associate professor of physics at Fordham University in New York City, tells Popular Mechanics .

.css-2l0eat{font-family:UnitedSans,UnitedSans-roboto,UnitedSans-local,Helvetica,Arial,Sans-serif;font-size:1.625rem;line-height:1.2;margin:0rem;padding:0.9rem 1rem 1rem;}@media(max-width: 48rem){.css-2l0eat{font-size:1.75rem;line-height:1;}}@media(min-width: 48rem){.css-2l0eat{font-size:1.875rem;line-height:1;}}@media(min-width: 64rem){.css-2l0eat{font-size:2.25rem;line-height:1;}}.css-2l0eat b,.css-2l0eat strong{font-family:inherit;font-weight:bold;}.css-2l0eat em,.css-2l0eat i{font-style:italic;font-family:inherit;} If an earlier industrial civilization did exist, and its extinction was the result of catastrophic climate change due to industrial activities, then we should heed the warnings.

A great rule of thumb exists in science, and it goes by the name Occam’s razor . In the 14th century, English Franciscan philosopher and theologian William of Ockham proposed that the likeliest solution to a problem is the simplest one. “That is very likely the case here,” says Holler. “We can largely explain the geologic record in terms of natural phenomena, so there is no need to invoke lost civilizations .”

However, if an earlier industrial civilization did exist, and its extinction was the result of catastrophic climate change due to industrial activities, then we should heed the warnings because, as a civilization, we stand at the precipice. “It will be a hard landing when we go over the edge, and we very well might not survive,” says Holler.

Greater Sustainability Leads to Fewer Signs

There is an oxymoron to the Silurian hypothesis: the more sustainable a society is in the way it generates energy and manufactures resources—arguably, the more advanced a society is—the smaller the footprint it will leave on the planet. Yet, this smaller footprint would translate to few markers on the geologic record for that period.

For example, the more plastic or persistent synthetic molecules we produce, the higher the chances future civilizations will find traces of us. (Our society produces 300 million tons of plastic each year worldwide—almost the equivalent of the weight of the entire human population!). Even if we wipe ourselves off the face of Earth with a nuclear catastrophe, long-lived radioactive particles will endure in the soil eons later, signaling we had existed.

“With the Silurian hypothesis, we articulated the kinds of signals that our civilization would leave if we disappear and somebody looks for our civilization 10 or 20 millions of years from now,” Frank says.

But most of all, the experiment demonstrated certain shortcomings in our current scientific apparatus. “In case an earlier species’s industrial activity was particularly short-lived, we would not be able to detect it in ancient sediments with the tools and methods we have now,” Frank explains. “If you want to look for evidence of a previous civilization, you’d have to do studies that nobody’s done and develop novel methods—for example, you’d have to figure out ways to look at the rock record on a much finer timescale.”

Remember, we are talking about millions of years of evolution of complex life and an unsparing Earth that grinds down everything in its wake. And though both Frank and Schmidt don’t really believe an industrial civilization existed before our own, the main takeaway of the Silurian hypothesis, Frank says, is that if you’re not explicitly looking for something, you might not even see it.

Stav Dimitropoulos’s science writing has appeared online or in print for the BBC, Discover, Scientific American, Nature, Science, Runner’s World, The Daily Beast and others. Stav disrupted an athletic and academic career to become a journalist and get to know the world.

.css-cuqpxl:before{padding-right:0.3125rem;content:'//';display:inline;} Pop Mech Pro .css-xtujxj:before{padding-left:0.3125rem;content:'//';display:inline;}

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RealClimate

Climate science from climate scientists...

The Silurian Hypothesis

17 Apr 2018 by Gavin

One of the benefits of working for NASA is that the enormous range of science the agency covers – from satellite records for the present day, to exoplanet climates, from early Mars and deep time on Earth to the far future – and the opportunity to think ‘big’. This week sees the publication of a paper I wrote with Adam Frank that we hope might provoke some ‘big’ thinking.

The Silurian Hypothesis ( preprint ) is the idea if industrial civilization had arisen on Earth prior to the existence of hominids, what traces would be left that could be detectable now? As a starting point, we explore what the traces of the Anthropocene will be in millions of years – carbon isotope changes, global warming, increased sedimentation, spikes in heavy metal concentrations, plastics and more – and then look at previous examples of similar events in the geological record. What is unique about our presence on Earth and what might be common to any industrial civilization? Can we rule out similar causes?

Adam had a nice piece in the Atlantic and there is also a good write up on Motherboard .

The naming of this idea comes from a 1970 Dr. Who episode where an ancient race of reptilians (“Silurians”) who had put themselves in hibernation to avoid a global catastrophe were awakened by experimental nuclear physics experiments. (I tried to find ‘prior art’ on pre-human terrestrial civilization that wasn’t based on notions of panspermia or ancient astronauts, but I haven’t yet been successful – anyone?). Needless(?) to say, we aren’t proposing any such occurrence (not least because the Silurian period is too early for the development of complex life on land).

The ideas in the paper lead naturally to many lines of speculation, some of which are relevant to us today, and some of which are just interesting (to us at least). For instance, given that the more sustainable a civilization is, the smaller its geophysical footprint might be, what does that imply for the detectability of long-term civilizations? Does the onset of ocean anoxia at the end of many of these events suggest a possibility of cycle where the collapse of one civilization provides the seeds (fossil fuels) for the next?

The whole idea is so intriguing that I wanted to do more with it than is possible in a journal article. Other scientists have occasionally dabbled in science-fiction (notably Carl Sagan and Fred Hoyle) and so, following their lead, I wrote a short story “Under the Sun” about the consequences for finding such a signal.

Literary as well as scientific criticism welcomed!

• G.A. Schmidt, and A. Frank, "The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?", International Journal of Astrobiology , vol. 18, pp. 142-150, 2018. http://dx.doi.org/10.1017/S1473550418000095

About Gavin

Reader interactions, 112 responses to "the silurian hypothesis".

17 Apr 2018 at 9:45 AM

Some additional comments and links on twitter:

https://twitter.com/ClimateOfGavin/status/985926956771430401

17 Apr 2018 at 10:39 AM

The pseudoscience folks refer to these as “Legacy Civilizations,” usually from the idea that the Pyramids are much, much older than they really are and various other objects are really “legacy artifacts” from vanished civilizations–Atlantis, Mu, etc. I think Asimov (1980) speculated that intelligence might repeatedly arise and be destroyed on a habitable planet, so that another term would be needed for the Drake equation–fraction of time an intelligent civilization actually exists during the habitable period.

I wonder what might succeed us if we wipe ourselves out. Rats and raccoons are pretty close to having hands.

17 Apr 2018 at 11:10 AM

Gavin, as surely as the stone age never ran out of stone, the anthropocene won’t hit Peak Prior Art any time soon-

https://vvattsupwiththat.blogspot.com/2013/02/postmodern-geochemistry-semiotic-carbon.html

17 Apr 2018 at 11:23 AM

Prior art… I can think of Harry Harrison’s “West of Eden”.

https://en.wikipedia.org/wiki/West_of_Eden

17 Apr 2018 at 11:35 AM

Interesting speculation. Since the larger the geophysical disruption, the easier it is to detect a previous civilization, there are a couple of interesting followups–what would be the change in our detectability following the different RCP’s over the next century or so, and what would minimize detectability? Is it possible to detect a “sustainable” civilization after a few million years?

17 Apr 2018 at 11:39 AM

There was an episode of Star Trek Voyager where they had an encounter with sentient dinosaurs from Earth who long ago migrated to a different quadrant in the galaxy. Very good episode, too.

17 Apr 2018 at 11:41 AM

As a Christian I would go so far as to subscribe to an Atlantis and/or a Lemuria. There could possibly be clues that the society that Cain in the Bible built was a very advanced society, intellectually and technologically. And this was 1,500-2,000 years before the Biblical flood.

17 Apr 2018 at 11:50 AM

Nice story (Under the Sun). A not entirely distant cousin to Asimov’s classic Nightfall.

17 Apr 2018 at 12:14 PM

One word: “Fantastic”!

17 Apr 2018 at 12:16 PM

17 Apr 2018 at 1:22 PM

“As a starting point, we explore what the traces of the Anthropocene will be in millions of years – carbon isotope changes, global warming, increased sedimentation, spikes in heavy metal concentrations, plastics and more – and then look at previous examples of similar events in the geological record. What is unique about our presence on Earth and what might be common to any industrial civilization?”

See the International Geosphere-Biosphere Programme’s Great Acceleration”. More here.

https://midmiocene.wordpress.com/2015/01/23/1950/

And now to read your story!

17 Apr 2018 at 1:44 PM

DAVID ALAN JONES RIDGE says: 17 Apr 2018 at 11:41 AM As a Christian I would go so far as to subscribe to an Atlantis and/or a Lemuria.

Could David be one one of the Mid Atlantic Ridges?

While deep time has pretty much caught up with the Old Testament and the New, the present epoch could use some more eras

17 Apr 2018 at 1:48 PM

#8, Ric–

Mmm, yeah. I see what you mean.

17 Apr 2018 at 1:52 PM

Isn’t there a “negative space” aspect to consider? Any civilisation that comes after us will have to contend with a lack of easily-accessible deposits of iron, copper, tin, coal, oil etc.

You argue that anoxic exents leading to mass carbon deposition might form the future fossil fuel beds… how long will it take for anything that’s buried on the ocean floor during the Anthropocene to become near-surface accessible on land? A putative future civilisation won’t start off with access to deep-sea drilling rigs, fracking capability, etc., it needs to work with what’s accessible via open pit shallow mining.

Similarly, the fact that our own Industrial Revolution was build on coal beds dating to the Carboniferous rather seems to suggest that no other intervening civilisation got there first!

17 Apr 2018 at 2:02 PM

“Right. You need to generate really large numbers of free and energetic neutrons. Like in a bomb. Oh…, oh, I see…”

Interesting and well written. I like it and hope you do more fiction. Of course the real evidence would have been if they found an oopart dated 55ma with something stamped on the bottom reading the equivalent of “ Made in Japan .

I’ve teased with a story like that.

https://midmiocene.wordpress.com/2017/11/22/the-last-option/

17 Apr 2018 at 2:53 PM

https://www.facebook.com/photo.php?fbid=10215517097658709&set=gm.1795014140557402&type=3&theater

17 Apr 2018 at 2:56 PM

So, thinking out loud here, wouldn’t there be fossil evidence no matter how squashed in sedimentary rocks: nuclear waste hazards, landfill linings, velociraptors with titanium hip replacements, that sort of thing?

I was sort of intrigued by this in terms of some ‘concurrent art’, Bears Discover Fire , by Terry Bisson. (“The premise is that bears have discovered fire, and are having campfires on highway medians.”* But then I discovered that Michael Bishop was inspired by this to write a story entitled Bears Discover Smut and got distracted.)

Anyway, I know it’s not exactly the point of the exercise, but you have to wonder what would need to happen to lizard brains (and why) in order to make the leap to industrialization. How would that shape the kinds signals they’d leave behind?

Just wondering…

—— *Wikipedia.

17 Apr 2018 at 4:32 PM

I seem to recall a story about finding a gold (?) watch (?) in ancient sediments from a dinosaur civilization, but the details are lost to me.

Minor point:

“It turned out that Audrey III was as well suited to detecting pollution levels in local river mud as she was past climate anomalies.”

Should probably say “…as she was in detecting past climate anomalies.”

Major point:

You apparently are trying to split the story up into two time lines. That is difficult for the best authors, but in your case it’s just confusing. It looks like something you did at the last minute to make the story more “interesting” (it isn’t).

17 Apr 2018 at 9:52 PM

In my own fiction and past-future history it is peopled with other intelligences. Some truly fanciful (like “fairies” are Carboniferous super intelligences) to a Permian civilization that split 3 ways- one left, one stayed and the last one stayed but went into long term stasis. Based off the mammal-like reptiles as they were called. I chose the Therocephalians which are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic. Therocephalians (“beast-heads”) are named after their large skulls, which, along with the structure of their teeth, suggest that they were successful carnivores. Like other non-mammalian synapsids, therocephalians are described as mammal-like reptiles, although in fact, Therocephalia is the group most closely related to the cynodonts, which gave rise to the mammals. The earlier therocephalians were in many respects as primitive as the gorgonopsids, but they did show certain advanced features. The discovery of maxilloturbinal ridges in some specimens suggests that at least some therocephalians may have been warm-blooded. (And at one point they gift us an easy to build FTL drive globally.)

Not counting any we create there could be more to appear some based off of elephant offshoots and even further in the future to arboreal terrestrial cephelopods onward even greater time to creatures that wouldn’t look out of place in the Silurian arthropods with god-like powers.

As with the answer is there intelligent life out there? When and where? Say if only 2 such appear there in our galaxy say every 15 million years are so many pitfalls involved as we have found in our own species experience. It is a matter of timing. Wouldn’t have to be millions of years it could be by thousands of years and distances too great for us to ever travel at our present knowledge.

We are a lowly Type 0 civilization yet our accidental wrecking of our whole climate is Type 1 level. But it is a mess and ultimately deleterious to us and all life on our planet. My hypothesis is that that a civilization can cause disaster in the next level of development. Which means the trials and tribulations of intelligence, should be mature and fix our coming Hot House Earth sooner than Nature can do there will be others for other generations to contend with.

Gene Roddenberry understood the dilemma of intelligence and showed other species who also fell though they were thousands of years further in technology and intelligence. Thought experiments done as tv drama.

17 Apr 2018 at 11:39 PM

Well, it won’t last millions of years into the future, but, frankly, I think our longest-lived Legacies will be (a) the Carbon Dioxide we emit, and (b) our plastics.

After all, in terms of our collective influence on the planet, we are Carbon Dioxide.

18 Apr 2018 at 12:20 AM

As a sxity year old geologist I’ve spent a good part of my life looking at sedimentary, metamorphic and igneous rocks in all parts of N. America. The “past civilizations” questions is a tough one.

18 Apr 2018 at 1:24 AM

I7:”wouldn’t there be fossil evidence no matter how squashed in sedimentary rocks: nuclear waste hazards, landfill linings, velociraptors with titanium hip replacements, that sort of thing?”

Here you go, Roger —

https://vvattsupwiththat.blogspot.com/2014/11/petrology-for-poets.html

18 Apr 2018 at 1:55 AM

I enjoyed the story very much, although I concur with Greg that a double timeline in a short story is a little confusing.

18 Apr 2018 at 3:41 AM

>I think Asimov (1980) speculated that intelligence might repeatedly arise and be destroyed on a habitable planet, so that another term would be needed for the Drake equation–fraction of time an intelligent civilization actually exists during the habitable period.

Intelligence may well have arisen repeatedly, but it has to be linked with the ability to manipulate the environment in order to produce technology. Dolphins may be as intelligent, and have similar communication skills, as humans but the chances of them producing a metalworking technology seem to be vanishingly slim.

18 Apr 2018 at 6:44 AM

Some of the more environmentally aware dinosaurs were worried about the consequences of an accident with the new Iridium enriched fusion reactor. “If it goes off only the cockroaches and mammals will survive…” they said.

18 Apr 2018 at 7:15 AM

The Silurian Hypothesis? Given the state of the real climate of the world this ‘big thinking work’ by Gavin is very sad. This article and the paper says a lot but not a word about climate science or how to improve the world and focus on sustaining life.

I find it a disgrace to everyone at Nasa/Giss and to anyone who has ever lifted a finger to support climate science.

Because it is all Ego all the way down.

18 Apr 2018 at 7:28 AM

I’ve had a variety of speculations around the related topic of the Fermi Paradox. My most recent one is here.

https://broadspeculations.com/2017/09/24/im-still-here-where-are-the-aliens/

I think life is probably abundant in the universe but complex life not so much. It takes a lot of planetary good fortune over a long period of time combined with fortuitous evolutionary sequences to get a big brained organism with ability to significantly manipulate the environment. I suppose some dinosaurs might have evolved this capability but then they had the planetary misfortune of the asteroid strike. The octopus, if it evolved to be out of the water and to live longer, might develop a civilization but that would need quite a bit of fortuitous evolutionary sequences.

So, all in all, I would say technological civilizations are probably rare in the universe and, even if they do not wipe themselves out, probably suffer some sort of cosmic misfortune. That only leaves a few fortunate (and wise?) civilizations to survive and it is unlikely ours will be in that group.

18 Apr 2018 at 8:19 AM

The Silurian Hypothesis by Dumb and Dumber?

This is what happens when non-experts who have no clue what they are doing think they know it all when they do not.

Ancient civilisation? Was prehistoric global warming caused by pre-human species

AN ANCIENT civilisation may have rose up and died out quickly scientists have said after discovering a short-lived but massive peak in global warming in pre-historic times.

A new study from a climatologist and a professor of astrophysics has revealed a massive spike in global warming 56 million years ago.

This spike was discovered in a dramatic change in the geological composition buried deep beneath Earth’s surface in an era known as the Paleocene-Eocene Thermal Maximum (PETM).

To investigate the idea of a possible pre-historic intelligent civilisation, the duo, Professor Adam Frank, of the University of Rochester and Gavin Schmidt, director of Nasa’s Goddard Institute for Space Studies (GISS), examined what evidence we, as humans, would leave behind if we were to become extinct.

Writing in The Atlantic, Professor Frank said: “There is a conundrum here. If an earlier species’s industrial activity is short-lived, we might not be able to easily see it.

https://www.express.co.uk/news/science/947879/ancient-civilisation-global-warming-life-climate-change

Some people have way too much spare time on their hands when they should be doing something more constructive and useful with the power of their Scientific position.

I expect calls for Gavin’s resignation as Lab Director for GISS to be coming thick and fast.

[ Response: I wouldn’t use the Express as a primary source for information on new scientific papers. Or indeed anything beyond the day of the week. – gavin]

18 Apr 2018 at 8:23 AM

The Henson TV series Dinosaurs “..is initially set in 60,000,003 BC in Pangaea. The show centers on the Sinclair family: Earl Sinclair (the father), Fran Sinclair (née Phillips – the mother and Earl’s wife), their three children (son Robbie, daughter Charlene, and Baby Sinclair) and Fran’s mother, Ethyl.

Earl’s job is to push over trees for the Wesayso Corporation with his friend and coworker Roy Hess where they work under the supervision of their boss Bradley P. Richfield.”

https://en.wikipedia.org/wiki/Dinosaurs_(TV_series)

18 Apr 2018 at 9:49 AM

Russell @ ~ 22

I’m digging it! (So to speak. And glad that you kept the p-chem to a minimum…) :-)

Now who is Roger?

18 Apr 2018 at 10:12 AM

My stupid iPad hangs whenever I try to access the story at Motherboard. Is it mirrored?

I’ve scanned the paper, and it looks convincing so far–to me at least.

I wonder how far ideas have to spread before they reach critical mass and catch on, spreading even farther–which might increase the strength of the signal and incidence of fossils.

Raccoons do have hands, and if I understand correctly they are even more innervated than humans since they rely on them so heavily for exploring their environment. Life span and amount of time spent learning before adulthood may be limiting factors in developing a material culture… or maybe not. I have great hope for raccoons as a replacement species for humans.

Or maybe lemurs will get it right.

18 Apr 2018 at 10:43 AM

It’s a well-plotted narrative. It reads more like a treatment than a conventional short story.

That’s a hint. It wouldn’t be too tough to get this in front of Netflix, Amazon or Hulu. Disney has a website where you can submit this type of thing online–I think one of the other major studios does too.

18 Apr 2018 at 11:10 AM

Time to call attention to the book “Out of Antarctica” – which uses cultural clues to suggest that humans once lived on that continent and left as the original climate migrants. No proof, only conjecture supported by plausibility. https://www.amazon.com/Out-Antarctica-Reflections-origins-peoples/dp/1902699459

One paper at https://www.sciencedirect.com/science/article/pii/S1055790309004965 mentions the, “Divergence of the Pleurobranchinae into the Antarctic Tomthompsonia and the remaining species in Early Oligocene coincides with two major geological events; namely the onset of glaciation in Antarctica and the opening of the Drake Passage with following formation of the Antarctic Circumpolar Current (ACC). These sudden and dramatic changes in climate probably led to subsequent migration of the last common ancestor of the remaining Pleurobranchinae into warmer regions, while the ACC may have accounted for larval dispersal to the Eastern Atlantic.”

18 Apr 2018 at 11:30 AM

Suppose intelligence had arisen in much earlier life forms, and they determined that their continued emissions of oxygen would have significant consequences on the planet, so they decided to stop their emissions.

18 Apr 2018 at 1:14 PM

https://www.atmos-chem-phys.net/18/5147/2018/acp-18-5147-2018.pdf

global average sfc T anomalies [as] indicative of anomalies in outgoing energy…is not well supported over the historical temperature record in the model ensemble or more recent satellite observations

18 Apr 2018 at 3:23 PM

Excellent little essay. There is almost certainly intelligent life out there in the universe, but what are the chances of such life going through the long series of inventions and discoveries that eventually lead humans to harness electricity? And having all the suitable materials? Not high one would think.

18 Apr 2018 at 5:29 PM

Oh surely you have entertained the notion of finding a little IC or microprocessor chip or the like lying amongst the brachiopods or trilobites every time you visit a sedimentary rock outcrop…

I certainly entertain such thoughts whenever I pick around an outcrop… just for fun of course…

18 Apr 2018 at 5:34 PM

Peter Ellis wrote @14: “ Isn’t there a “negative space” aspect to consider? Any civilisation that comes after us will have to contend with a lack of easily-accessible deposits of iron, copper, tin, coal, oil etc. ”

Coal and oil yes, as they are combustible, but homo sapiens have quite nicely concentrated iron, copper, tin and other metals into multiple deposits of far higher purity than those found in nature. We know them as garbage dumps, scrap yards, factories and cities.

18 Apr 2018 at 6:39 PM

Great story Gavin. Well-written, readable, thought-provoking, meaningful but not preachy. The publication of fiction has can stimulate public awareness nearly as much as the publication of scientific articles. Here’s a poem recently written by a chum, touching on your field. Thanks for your continuing work.

Out on a Record-Breaking Warm Saturday in January by Tim Gillespie

The shocking day: the sun blinding, gloves crammed in my pocket, jacket over my arm, steam rising from the drying-out, early flowering viburnum and daphne in the air— a bounty so unexpected, a slap of joy.

“Beautiful day,” I say to a woman digging in her yard. We’ve nodded other times when I’ve walked by her house a half-mile from mine. “Yes,” she says, “unseasonably warm,” brushing back a strand of hair with her muddy glove. “I wonder what it means, though,” she says, her trowel plunging into the dirt, “and if we should worry.”

The what-it-means: glacial melting, coral reefs bleached of life, tsunami and storm surge, rising seas swamping small villages, drought looming and fire and mudslide to follow—- a small scent of wintersweet punches my nose.

-In Windfall: A Journal of Poetry of Place, spring 2018 issue

18 Apr 2018 at 11:11 PM

“For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much—the wheel, New York, wars and so on—whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man—for precisely the same reasons.”

Douglas Adams

19 Apr 2018 at 1:14 AM

I just skimmed this pre=print in about 60 seconds. Interesting enough that I’ll read it, later. This is what stood out to me:

The longer human civilization lasts, the larger the signal one would expect in the record. However, the longer a civilization lasts, the more sustainable its practices would need to have become in order to survive. The more sustainable a society (e.g. in energy generation, manufacturing, or agriculture) the smaller the footprint on the rest of the planet. But the smaller the footprint, the less of a signal will be embedded in the geological record. Thus the footprint of civilization might be self-limiting on a relatively short time-scale

I’ll need to read it more carefully. But that stood out like a sore thumb in seconds of skimming. Interesting point to spend more time thinking about.

19 Apr 2018 at 1:35 AM

I think Lovecraft’s ‘At the Mountains of Madness” counts.

19 Apr 2018 at 9:33 AM

I really enjoyed reading the story – apart from the drama of the dawning insight into what happened, it’s a great way of talking about the arc of publishing a scientific advance – the trepidation, the cautious publication, the media frenzy and the reactions of colleagues. And then the questions that arise from those new insights … One missing component (next episode, extinction permitting?) would be the story of identification of the technological species. With human geological debris (in the event of a sudden extinction) this would be fairly straightforward – the skulls with the largest brains, the plastic models showing miniature humans using technology, the scale and structural adaptions of the technology (eg cars) … with a much older species, who knows? there might have been many large-brained Eocene bipeds in this alternative world, but depending on the way they disposed of their dead, it might not be easy to find fossils of them. They might not have been as fond of plastic (or similar) models. But the associations between a species and its technology would probably still be reasonably clear. Humans will leave a massive geologial “footprint” – roads, rubbish dumps, graveyards, buildings, shipwrecks – that will still be reasonably clear in a hundred million years’ time – unless we clear up after ourselves … Thanks for the great story!

19 Apr 2018 at 2:19 PM

Any evolving intelligence throughout the Universe will at one point discover the climate trigger. A primary requirement is likely a stable period priori. A species which is unaware of the climate trigger, will likely also not be able to hibernate.

Given these circumstances we could make a metaphor for this climate situation, comparing it with an organisms puberty phase. The question is to what extent we will play with the climate trigger game, and the question is what it entails on longer time scales. For instance does it means dwarfing, wide spread species retardations, chain extinctions …

19 Apr 2018 at 2:46 PM

Sometimes the truth can be stranger than fiction. Judging by the d13C spike, the PETM was caused by the oxidation of organic carbon, just as we are doing now. However, there seems to have been an additional source of CO2, so the oxidation of organic carbon was just the trigger for the release of even more carbon dioxide.

We have already released more CO2 than that which triggered the PETM extinction. Will our emissions trigger further emissions as happened in the PETM? I have evidence to suggest the answer is yes.

Will the scramble for scarce resources when temperatures soar trigger a nuclear war? I hope not.

19 Apr 2018 at 4:23 PM

https://twitter.com/omarvaid/status/987061149693857792

19 Apr 2018 at 7:17 PM

I agree with Radge Havers, #17: where are all the fossils? The fact of a civilisation being sustainable does not exclude recyclable materials leaving a trace. For example, just down the road from where I live we have fossil tree (not really a tree, more like an enormous horsetail) dating from over 300 million years ago, found well preserved in the Durham coal measures, and showing lovely detail of its bark and roots. Well a tree is pretty recyclable, it’s just a load of wood and cells after all, and it has evolved to decompose, but this one still got preserved. Regarding the past civilisations, during their development phase they must have had artefacts, surely? Or tools? Factories? Vehicles? Dwellings? And the creatures themselves of course, maybe wearing some sort of clothing or body protection? Natural processes of weathering, transport and sedimentation can still allow the feather imprints of archaeopteryx to be preserved, or the delicate structures of certain leaves or invertebrates, so I think it is reasonable to expect the ‘people’ of these civilisations would have left something behind, including occasionally fossils of themselves and what they wore, or the things they carried. If they had spread out across the whole planet, one might even expect to find assemblages of them sometimes, rather like the fossil community clusters seen in the Burgess Shale or the Rhynie Chert.

19 Apr 2018 at 11:23 PM

Unless this civilization only occupied a small area, I would think there would be ample fossil evidence. We are calling the present the Anthropocene, we have come to have a huge influence of the planets environment, not just by a CO2 spike, but in many other ways, including enhanced erosion. The current civilization will have left important traces on this planet until such time as the sun becomes a red giant and melts all the rocks.

20 Apr 2018 at 9:22 AM

The astrobiology article on the Silurian hypothesis makes a very good accompaniment to the story – or perhaps the aricle is the main course, and the story is the dessert! Anyway, plenty of food for thought. The article emphasises the difficulties of identifying an unambiguous geochemical marker for industrial activity.While this is probably true of a marine core, any extensive terrestrial exposure of sediments from the period would have lots of evidence of human activity, especially onshore or nearshore uplifted sediments. Objects do not have to survive millions of years to be fossilised, they only need to last long enough for their shape to leave a distinctive geological trace. Otherwise dinosaur footprints and soft-bodied fossils would be non-existent. The remains of human artifacts and structures would be incredibly abundant relative to eg the terrestrial vertebrate record. Interpreting them might not be easy though – and what would they make of the sort of assemblage they would encounter in the debris of a natural history museum? Dinosaurs, trilobites, humans and mammoths all together in a single structure … lets hope the future geologists don’t have a creationist problem! It would be hard to rule out the hypothesis of an alien civilisation arriving (and then departing post-industrially) unless the geological history of the evolution of the industrial species could be reconstructed at least to some extent.

20 Apr 2018 at 3:11 PM

See The Toolmaker Koan by John C. McLaughlin

and his superior novel, The Helix and The Sword

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The silurian hypothesis.

The art and life of Mark di Suvero

In his monthly column,  Conspiracy ,  Rich   Cohen  gets to the bottom of it all. 

When I was eleven, we lived in an English Tudor on Bluff Road in Glencoe, Illinois. One day, three strange men (two young, one old) knocked on the door. Their last name was Frank. They said they’d lived in this house before us, not for weeks but decades. For twenty years, this had been their house. They’d grown up here. Though I knew the house was old, it never occurred to me until then that someone else had lived in these rooms, that even my own room was not entirely my own. The youngest of the men, whose room would become mine, showed me the place on a brick wall hidden by ivy where he’d carved his name. “Bobby Frank, 1972.” It had been there all along. And I never even knew it.

That is the condition of the human race: we have woken to life with no idea how we got here, where that is or what happened before. Nor do we think much about it. Not because we are incurious, but because we do not know how much we don’t know.

What is a conspiracy?

It’s a truth that’s been kept from us. It can be a secret but it can also be the answer to a question we’ve not yet asked.

Modern humans have been around for about 200,000 years, but life has existed on this planet for 3.5 billion. That leaves 3,495,888,000 pre-human years unaccounted for—more than enough time for the rise and fall of not one but several pre-human industrial civilizations. Same screen, different show. Same field, different team. An alien race with alien technology, alien vehicles, alien folklore, and alien fears, beneath the familiar sky. There’d be no evidence of such bygone civilizations, built objects and industry lasting no more than a few hundred thousand years. After a few million, with plate tectonics at work, what is on the surface, including the earth itself, will be at the bottom of the sea and the bottom will have become the mountain peaks. The oldest place on the earth’s surface—a stretch of Israel’s Negev Desert—is just over a million years old, nothing on a geological clock.

The result of this is one of my favorite conspiracy theories, though it’s not a conspiracy in the conventional sense, a conspiracy usually being a secret kept by a nefarious elite. In this case, the secret, which belongs to the earth itself, has been kept from all of humanity, which believes it has done the only real thinking and the only real building on this planet, as it once believed the earth was at the center of the universe.

Called the Silurian Hypothesis, the theory was written in 2018 by Gavin Schmidt, a climate modeler at NASA ’s Goddard Institute, and Adam Frank, an astrophysicist at the University of Rochester. Schmidt had been studying distant planets for hints of climate change, “hyperthermals,” the sort of quick temperature rises that might indicate the moment a civilization industrialized. It would suggest the presence of a species advanced enough to turn on the lights. Such a jump, perhaps resulting from a release of carbon, might be the only evidence that any race, including our own, will leave behind. Not the pyramids, not the skyscrapers, not Styrofoam, not Shakespeare—in the end, we will be known only by a change in the rock that marked the start of the Anthropocene.

It was logical for Schmidt and Frank to turn their attention from the upper to the under, from the cosmos to our own earth. Why look for alien life there when we might find it here, removed not by miles but years. There was indeed a mysterious jump in surface heat; 55 million years ago, global temperatures rose from 9 to 14 degrees Fahrenheit. Called the Paleocene–Eocene Thermal Maximum, it left the same sort of geological evidence that will be left by our current carbon binge. There may have been other jumps, but we wouldn’t know it, as the geologic record only goes back so far. (We live in a compactor, where all things are crushed, recycled, and returned as new.) A meteor could’ve caused the Thermal Maximum, or it could’ve been the eruption of a monster volcano, the sort that presently smolders beneath the Atlantic. Or it could have been caused by the awakening of an ancient civilization, which rose like we rose, then fell as we will. That could be the fate of all advanced species, a rise and fall that flows as naturally as the change of seasons. Such a universe is ironic, continually creating characters whose technology brings on the very end they’re trying to avoid.

When Schmidt and Frank searched, they found a single forerunner to their idea of deep time. It came not from science, but from science fiction. At this level of conjecture, there’s little difference. It was an episode of Dr. Who, in which the time traveler visits an ancient species of advanced, long-extinct lizard people who’d achieved technological mastery 450 million years before modern man. The lizards were called Silurians, hence the Silurian Hypotheses.

It’s not really a new idea. Ancient mystical texts hint at earlier creation, the life that preceded the Garden, prequels to Genesis. These incarnations are not reported in the Bible because they are none of your goddamn business, but the evidence is everywhere. Some students of conspiracy believe there was a time when lizard people shared the earth with modern men, the older race dying as the younger emerged from the forest. The last of the lizards were worshipped as gods; these were the deities of ancient India and Greece. The technology—weapons and machines—created miracles. You can see the lizard kings in carvings from Mesopotamia, the oldest historical records, where humans bow before reptile men. You find them again in the Torah, where they appear as Nephilim, the so-called watchers—“The Nephilim were on the earth in those days and also afterward when the sons of God went to the daughters of humans and had children by them,” according to Genesis, “they were the heroes of old, men of renown”—which no priest, minister, or rabbi can properly explain. Just ask a clergyman and see for yourself. (I asked my rabbi.) There is some weird shit in the Bible.

According to a kabbalah-besotted friend, this world is God’s seventh creation, which explains dinosaur bones and other fossils. “The evidence is everywhere,” he told me one night. “They can say a meteor wiped out the past, but what is a meteor? God.” Some believe there are still Silurians walking the earth, holdovers who share their technology with a hidden elite—possibly Freemasons, possibly Jews. Some pseudoscientists speak of an atomic blast that took place in India 10,000 years ago. It might’ve been a natural phenomenon, or might’ve been the war that wiped out the Silurians or drove them off the earth. A website called Vedic Knowledge reported evidence “of an atomic blast dating back thousands of years. It destroyed most of the buildings and probably a half-million people in Rajasthan, India. One researcher estimates that the bomb used was about the size of the ones dropped on Japan in 1945.”

This ancient catastrophe, which some take as evidence of an ancient nuclear war, shows up in the Mahabharata, a Sanskrit epic, with the appearance of “a single projectile charged with all the power in the Universe … An incandescent column of smoke and flame as bright as 10,000 suns, rose in all its splendor … it was an unknown weapon, an iron thunderbolt, a gigantic messenger of death which reduced to ashes an entire race.”

It’s heartbreaking—the fact that, as we face the nightmare of climate change, some of us have read our own perilous present back into the geological past and have come to see even our apocalypse as unremarkable, something that’s been experienced before and was inevitable from the start. It’s thrilling, too, the idea of a pre-human industrial civilization. It means we don’t know anything: who we are, or where, or even the history of our own home.

Read more of  Rich   Cohen’s Conspiracy column here.

Rich Cohen is the author of  The Last Pirate of New York: A Ghost Ship, a Killer, and the Birth of a Gangster Nation .

Toroidally focused ultrasonic flaw detectors

• Acoustic Methods
• Published: 28 July 2011
• Volume 47 , pages 308–310, ( 2011 )

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• A. V. Shevelev 1 &
• Zh. V. Zatsepilova 2  

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New-type toroidally focused ultrasonic flaw detectors, whose application provides an appreciable increase in the flaw detection rate with retention of high sensitivity to flaws, are considered. The construction of a flaw detector is presented, the sizes of a gauge for the formation of the toroidal surface of a lens are given, and the technology of the manufacturing of a toroidal lens is described.

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Nerazrushayushchii kontrol’ (Spravochnik) (Nondestructive Testing: Handbook), Klyuev, V.V., Ed., vol. 3: Ul’trazvukovoi kontrol’ (Ultrasonic Testing), Moscow: Mashinostroenie, 2006.

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Original Russian Text © A.V. Shevelev, Zh.V. Zatsepilova, 2011, published in Defektoskopiya, 2011, Vol. 47, No. 5, pp. 19–22.

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Shevelev, A.V., Zatsepilova, Z.V. Toroidally focused ultrasonic flaw detectors. Russ J Nondestruct Test 47 , 308–310 (2011). https://doi.org/10.1134/S1061830911050093

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Received : 14 January 2011

Published : 28 July 2011

Issue Date : May 2011

DOI : https://doi.org/10.1134/S1061830911050093

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