The Silurian Hypothesis: Researchers Discuss The Chances Of Intelligent Life Existing Before Humans

The thought of dinosaurs and other prehistoric creatures having proper names, working jobs to feed their families, and enjoying the trappings of technology is one that’s fueled many a children’s cartoon or fantasy story through the years. But with the proof of an intelligent civilization bound to get destroyed forever after millions of years, there might be an outside chance that humans were not the first intelligent, industrialized civilization in Earth’s history. That’s the gist of the so-called “Silurian Hypothesis,” which was explored by a pair of researchers in a recent thought experiment.

In a new paper written by University of Rochester astrophysicist Adam Frank and NASA Goddard Institute for Space Studies director Gavin Schmidt and published in the International Journal of Astrobiology, the two researchers sought to answer several questions about the human race as we know it, and the possible ways in which civilizations can prove the existence of mankind millions of years into the future, should humans be completely extinct at that time.

“Gavin and I have not seen any evidence of another industrial civilization,” Frank clarified, in a statement quoted by Science Daily.

“[But] These questions [asked in the study] make us think about the future and the past in a much different way, including how any planetary-scale civilization might rise and fall.”

Although it shares a name with a prehistoric era that took place well before the rise of amphibians and reptiles, the Silurian Hypothesis, which was also the name Frank and Schmidt used for their paper, was inspired by a completely different source. According to Newsweek, the inspiration came from the Silurians, an intelligent reptilian race from Doctor Who that, per the popular science fiction series’ narrative, existed on Earth several hundreds of millions of years ago, and walked on two feet, much like today’s humans do.

In order to determine the answers to the questions posed by the study, Frank and Schmidt elected to define civilizations by their use of energy, which is relevant as humanity’s influence on Earth’s climate and environment is a key feature of the Anthropocene period. Although the Anthropocene has yet to be listed as an official geological era, Schmidt told Newsweek that humans are leaving quite a footprint on our planet’s geological record, as evidenced by animal extinctions linked to man-made factors, and the existence of plastics and synthetic chemicals, among other factors. The researchers also stressed that this is also manifested through global warming, which is largely driven by the burning of fossil fuels.

“We are already a geophysical force, and our presence is being recorded in carbon, oxygen and nitrogen isotopes,” Schmidt commented.

Keeping that in mind, Schmidt and Frank presented their “Silurian Hypothesis,” pondering the chance that another intelligent species lived on Earth hundreds of millions of years ago. According to Schmidt, it is indeed “possible” that intelligent civilizations existed before we did, though there’s no tangible proof of that being the case.

“It might also be that all such traces [of previous civilizations] have been ground to dust and that the only remaining traces are in the more subtle perturbations in geochemistry,” Schmidt told Newsweek, adding that it’s also possible evidence “could have been missed” in the case of a civilization that lasted only a few thousand years.

Given the ongoing problem of man-made climate change, Science Daily cited Schmidt, who believes there could be an ironic twist in play if cleaner and more environmentally safe forms of energy become prevalent — the chance that less evidence of our existence would be left behind should humans go extinct in the very distant future.

In all, the main takeaway of Schmidt and Frank’s “Silurian Hypothesis” might be how it could be used to guide scientists as they search for intelligent extraterrestrial life. As planets like Mars and Venus are believed to have been more habitable in the distant past than they currently are, Schmidt stressed that exploring each planet’s geological sediments could help researchers “think about what [they] should be looking for.”