If a technologically advanced species existed on Earth before us, they may have left a trace.
The Silurians, a technologically advanced species of humanoid reptile that predated humans and went into hiding before being rediscovered by everyone’s favorite time-traveling extraterrestrial in his phone box, are mentioned in the Doctor Who series. Science isn’t working thus far. However, two researchers from the University of Cambridge gave the imaginary species its own paper title in 2018. It was titled The Silurian hypothesis: would it be feasible to discover an industrial society in the geological record?
The article, which was published in the Journal of Astrobiology, did not make the case that a technologically advanced species existed before humans but instead posed the intriguing hypothetical question of whether it would be possible to discover “geological fingerprints” of a long-gone civilization that vanished millions of years ago.
Understanding how frequently an industrial civilisation develops, assuming that life has arisen and that some species are intelligent, is one of the major questions in estimating the possibility of discovering such a civilization, the authors write in the paper.
“The only known example is that of humans, and our industrial civilisation has only existed for about 300 years (since, for example, the beginning of mass production methods). This is a very small portion of the period that our species has existed and of the time that sophisticated life has existed on the land surface of the Earth.”
The obvious question of whether something could have happened earlier is raised by the brief time frame.
In addition to being an intriguing concept, attempting to find an answer may aid in our hunt for evidence of advanced civilizations on extrasolar worlds. According to the research, humans have altered the Earth’s climate and ecosystems, leaving noticeable scars on the globe that will undoubtedly stay for many years. That doesn’t imply that these changes will be obvious after a few million years, though. In actuality, the record we leave may only be a few millimeters thick—for instance, in the sediment. Even if we live considerably longer than our current age, this might still remain the case.
The team writes, “The stronger the signal one would predict in the record, the longer human civilisation lasts.” “A civilization’s customs would have needed to be more resilient to survive the longer it existed. The impact on the rest of the earth is reduced in societies that are more sustainable (in terms of, say, energy production, industry, or agriculture). But the less of a signal will be preserved in the geological record, the smaller the footprint.”
The group discusses additional signs we might leave for another species in a few million years (or that may have been left for us). Others would be blatant indications that we were here and completely destroyed the area, while some will be indistinguishable from naturally occurring phenomena like the Cretaceous and Jurassic ocean anoxic events.
In the event of a nuclear disaster, the team hypothesizes that several specific tracers would stand out, specifically persistent synthetic chemicals, plastics, and (perhaps) very long-lived radioactive fallout.
“Without those markers, the uniqueness of the event may well be recognized in the variety of relatively independent fingerprints rather than a coherent set of changes linked with a single geophysical source,” the study stated.
In the report, the team doesn’t provide a conclusive response, but they do speculate that, if any such ancient advanced species were to be found, they would be detected by looking into elemental and compositional anomalies in the sediment record.
They write, “While we strongly doubt the existence of any prior industrial civilization before our own, posing 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.”
In order to be better equipped to respond to our title question in the future, we hope that our study will serve as inspiration to tighten the limitations on the hypothesis.
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