“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?”
That’s the opening question asked by Gavin A. Schmidt and Adam Frank in their new research paper, “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?”, in which they look for geological fingerprints of advanced civilizations that may have lived on Earth before our own and been wiped out by some sort of extinction cataclysm. Did they find it?
Adam Frank, professor of physics and astronomy at the University of Rochester, describes the jaw-dropping research proposal presented to him by Gavin Schmidt, the director of the NASA Goddard Institute for Space Studies, in an excellent article in the current edition of The Atlantic. It follows the publication of the study (also an excellent read) in the International Journal of Astrobiology.
“Humans are the only example [of an industrial civilization] 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.”
However, it’s big enough to have a physical impact on the surface of the Earth – an impact that would be evident to future researchers digging thought the layers of the planet’s crust millenniums from now. Frank and Schmidt start here, because that industrial civilization evidence may be the same thing we need to be looking for to find past civilizations.
But first … the name.
“We name the hypothesis after a 1970 episode of the British science fiction TV series Doctor Who where a long-buried race of intelligent reptiles "Silurians" are awakened by an experimental nuclear reactor. We are not however suggesting that intelligent reptiles actually existed in the Silurian age, nor that experimental nuclear physics is liable to wake them from hibernation.”
Of course, you Doctor Who fans already knew this. A name you may not recognize is “Anthropocene,” which is the moniker proposed for our current geological period. What would identify the Anthropocene age to future geologists? The study points to evidence of fossil fuel usage, plastics (our garbage), agriculture (fertilizers and erosion), pollutants, unusual radioactive isotopes (from nuclear war or meltdowns) and climate change (variations in carbon dioxide, methane, etc.). While these are indicators of the existence of an industrial civilization, they may also be indicators of what killed it.
Then again, what if the advanced civilization was more advanced than we Anthropocene beings. If they no longer used fossil fuels, would we find dead batteries instead? There’s also the question of how long the civilization was industrial. We’ve only been there for 300 years. Even if it lasted 100,000 years, after millions of years, would there be any evidence left? How thin would that layer be?
As you may have guessed, Frank and Schmidt didn’t find evidence of a past advanced civilization yet … nor did they find the Silurians (which may be good news because they’d probably want royalties (or something more painful) for the use of their name). However, they point out that looking for evidence of past industrial civilizations on Earth provides knowledge that will help determine if other planets had similar now-extinct advanced life forms. They also warn that, while they have found clear evidence of other periods of global warming/climate change that match what we’re going through (the Paleocene-Eocene Thermal Maximum 56 million years ago, for example), that period did not match “the speed at which we’re dumping fossil carbon into the atmosphere … never before in the planet’s multibillion-year history has so much buried carbon been dumped back into the atmosphere so quickly.”
Will the only evidence of the Anthropocene age be a thin black residue in the Earth’s crust? Maybe we should stop looking for past civilizations and start looking in the mirror.