Guest essay by Eric Worrall
Would it be possible to distinguish the fall of a pre-human civilisation destroyed by industrial CO2, from a natural climate upheaval?
A New Study Suggests There Could Have Been Intelligent Life on Earth Before Humans
Looking for aliens across deep space is great, but have we looked hard enough in our own terrestrial backyard—here on Earth?
Apr 17 2018, 1:13am
One author of the new study, leading climatologist Gavin Schmidt, wrote a work of fiction to explore its findings. Read ‘Under the Sun’, which we published at Terraform alongside the following piece.
The human yearning to connect with other intelligent life-forms runs deep, and it has become the driving force behind a dazzling range of scientific pursuits. From the SETI Institute’s radio sweeps of the sky, to the discovery of liquid water on neighboring worlds, to the thousands of exoplanets detected over the past two decades, there have been major gains in chasing one of the ultimate cosmic mysteries—whether or not we are alone in the universe.
Outside of some science fiction stories and a speculative paper by Penn State astronomer Jason Wright, little serious thought has been afforded to the possibility that we humans are not the first species to build an advanced civilization in the solar system’s history.
“It actually hasn’t been explored that much,” climatologist Gavin Schmidt, director of the NASA Goddard Institute for Space Studies in New York, told me over the phone. “It never gets brought up as a potential thing that you want to look for.”
So, Schmidt paired up with University of Rochester physicist Adam Frank to co-author a paper entitled “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?” The hypothesis borrows its “Silurian” title from the fictional reptilian species depicted in the science fiction franchise Doctor Who—these scaly Silurians flourished on Earth many millions of years before the dawn of our own society.
“There’s lots of things that are going well for [human civilization], but there’s a big price that’s being paid in the ecology and biology,” Schmidt told me. He emphasized that many of these consequences can seem to be “out of sight, out of mind” due to conveniences like sewage infrastructure and garbage relocation. But when considered in totality, anthropogenic activities really add up, and impact the geological record. “All of the waste and footprint is being hidden from us, but it isn’t hidden from the planet,” he said.
It’s unlikely that any massive telltale structures would remain preserved through tens of millions of years of geological activity—that holds true for both human civilization and any potential “Silurian” precursors on Earth.
Instead, Schmidt and Frank propose searching for more subtle signals, such as byproducts of fossil fuel consumption, mass extinction events, plastic pollution, synthetic materials, disrupted sedimentation from agricultural development or deforestation, and radioactive isotopes potentially caused by nuclear detonations.
“You really have to dive into a lot of different fields and pull together exactly what you might see,” Schmidt said. “It involves chemistry, sedimentology, geology, and all these other things. It’s really fascinating.”
The abstract of the study;
The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?
Gavin A. Schmidt (a1) and Adam Frank (a2)
https://doi.org/10.1017/S1473550418000095Published online: 16 April 2018
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.
Read more (paywalled): https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/silurian-hypothesis-would-it-be-possible-to-detect-an-industrial-civilization-in-the-geological-record/77818514AA6907750B8F4339F7C70EC6
Sadly the full study is paywalled, but I think we get the idea.
The previous referenced study was by Penn State Astronomer Jason T. Wright, which concluded that it might be easier to detect traces of any previous high tech civilisation by any technical artefacts they left on other planets or on Asteroids.
I’m skeptical of theories of past civilisations, because it is difficult to imagine an event or series of events which would completely finish off an established intelligent species, especially omnivores like humans, unless that species had a specific fragility which made it especially vulnerable.
Consider the hideous aftermath of the Cretaceous–Paleogene extinction event, plants dead or dying, rotting corpses littering the landscape, a bonanza for cockroaches and scavengers. If something similar happened today, the luckiest and most determined humans would more than likely survive; if all else fails, humans can eat cockroaches.
Schmidt has also written a short fictional account about the discovery of traces of a pre-human civilisation which destroyed itself through nuclear war.
If traces of artificial isotopes were discovered, as in Schmidt’s short story, such a discovery would not necessarily end the debate. The presence of artificial isotopes is not necessarily the fingerprint of the nuclear technology of an ancient pre-human civilisation. 1.7 billion years ago a natural nuclear reactor fired up in Africa, creating artificial isotopes as byproducts of an uncontrolled natural fission reaction.
UPDATE: Gavin Schmidt has posted about it on “RealClimate” here