Could a Civilization Vanish without a Trace? The Silurian Hypothesis

If an advanced industrial civilization had existed on Earth one hundred million years ago, a civilization with cities, roads, energy systems, and technology, would we be able to find any evidence of it today?

According to two astrophysicists who explored this question in 2018, the answer is: probably not much.

The Thought Experiment

In 2018, Gavin Schmidt and Adam Frank published what they called the Silurian Hypothesis, a nod to the intelligent reptilian Silurians of Doctor Who, not the geological period. The paper was not an argument that ancient civilizations existed. It was a scientific thought experiment that asked a deceptively simple question: what traces would a past industrial civilization leave in the geological record, and how detectable would those traces be?

Their answer is sobering. Human civilization has existed for only a few thousand years. Our industrial age spans roughly 250 years. In a few million years, the cities, roads, satellites, and monuments of the modern world will have eroded, been buried, or been recycled by plate tectonics. What would remain?

The Fingerprints of Industry

Schmidt and Frank identified several potential geological signatures:

·        unusual carbon isotope ratios from burning fossil fuels

·        rapid temperature spikes in ancient sediments

·        concentrations of heavy metals from industrial processes

·        nitrogen cycle disruptions from large-scale agriculture, and

·        trace quantities of synthetic materials that do not occur naturally.

These are subtle signals — the kind that a careful geochemist might find interesting without immediately concluding that someone was once running a factory.

Schmidt and Frank argue that the shorter the civilization and the longer the time since it existed, the harder it becomes to detect. A civilization lasting only a few centuries, millions of years ago, would leave faint chemical whispers at best. Remember Gollum’s famous riddle in The Hobbit, the one that Bilbo eventually got, albeit accidentally. Time ultimately devours all things.

The Paleocene-Eocene Thermal Maximum, a natural warming event 56 million years ago, already produced the kind of carbon isotope signature that an industrial civilization might leave. Although the PETM produced some of the same carbon-isotope signatures that an industrial civilization might leave, its carbon release occurred over thousands of years rather than centuries. Combined with extensive evidence for volcanism and other natural processes, most geologists conclude that natural causes remain by far the most likely explanation. Think of Occam’s razor (the simplest explanation requiring the fewest assumptions is generally preferred).

The 1968 film Planet of the Apes offers a vivid dramatization of this idea. The scene that resonates in my mind is not the famous Statue of Liberty ending, but an earlier one. Cornelius leads a dig into an ancient cliff face and unearths human artifacts buried deep in the rock strata: fragments of technology, remnants of a civilization so thoroughly erased that the apes who now rule the planet have no memory of it whatsoever. The evidence is there, compressed into geological layers, invisible without a careful excavation. Were we to make a similar discovery about an ancient civilization, would our governments choose to bury the information as Dr. Zaius did or make it public? A similar question arises in the debates around the existence of UFOs (which is the subject of a future newsletter).

Ruins at Cobá in Mexico’s Yucatán Peninsula. Cobá’s power declined after about A.D. 1000, although portions of the city remained in use for centuries. In this tropical environment, roots and vegetation have already begun reclaiming its massive stone structures. Photograph by John Topping.

What This Means for Atlantis

The Silurian Hypothesis is often cited by Atlantis enthusiasts, but Schmidt and Frank were careful to clarify: their paper is not an argument for any ancient civilization. It is an argument about detectability.

But here is where the hypothesis becomes genuinely interesting: it demonstrates that the absence of obvious ruins is not, by itself, proof that no ancient civilization ever existed. Absence of evidence is not evidence of absence — and the Silurian Hypothesis provides a scientific framework for understanding exactly why. Occam’s razor, while useful, is not the be all and the end all. History is replete with cases where new evidence ultimately proved the more complex explanation to be correct.

Plato’s Atlantis is said to have been destroyed roughly 9,600 BC — about 11,600 years ago. That is recent enough, on geological timescales, that evidence should still be findable. But are we looking in the right places? And, if we find evidence, will we recognize it for what it is?

If Atlantis had existed one million years ago (as it does in my Atlantis Universe) instead of roughly 12,000 years ago, how much evidence would remain? Perhaps more than we might think—but probably far less than most people imagine.

Source: “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?” Gavin A. Schmidt & Adam Frank, International Journal of Astrobiology, 2018. Legacy of Atlantis by John Topping, published by The Story Plant / Gramarye Media.