Climatologist Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, together with Adam Frank, a scientist at the University of Rochester, decided to investigate this assumption and wrote together an article called “The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?”.
The term “Silurian” was borrowed from the British science fiction series “Doctor Who,” which refers to a reptilian race that lived on Earth millions of years before the emergence of our own society.
Published in the International Journal of Astrobiology, the work describes the type of signature that a technologically competent species can leave behind.
Schmidt and Frank use projected traces of the Anthropocene, the current era in which human activity is influencing planetary processes such as climate and biodiversity, as a guide to what we might expect from other civilizations.
It is worth remembering that any massive telltale structures are unlikely to remain preserved over tens of millions of years of geological activity, this is true both of human civilization and any possible “Silurian” precursors on Earth.
Instead, Schmidt and Frank propose looking 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 delve into a lot of different fields and gather what you can see. It involves chemistry, sedimentology, geology and all these other things. It’s really fascinating,” says Schmidt.
Drake Equation
The scientists’ article relates the Silurian hypothesis to the Drake equation, which is a probabilistic approach to estimating the number of intelligent civilizations in the Milky Way, developed by astronomer Frank Drake.
One of the main variables in the equation is the time that civilizations are able to transmit detectable signals.
One proposed reason why we have not achieved contact with an alien species is that this “length of time” variable may be extremely short, either because technologically advanced civilizations self-destruct or because they learn to live sustainably on their home worlds.
“It is possible that the detectable period of a civilization is much shorter than its actual longevity, because you, the humanity, cannot last very long doing the types of things we are doing. You either stop because you screwed up, or you learn not to. Either way, the explosion of activity, waste and massive amounts of trails is actually a very short period of time. Maybe this has happened 1 billion times in the Universe, but if it only lasted 200 years every time, you would never see it,” Schmidt explained.
Silurian Hypothesis
The same logic holds true for any previous civilizations that may have arisen on Earth, only to collapse into ruins or curtail activities that threaten their lifespan.
There are definitely some not-so-subtle lessons that humans can take away from this forked path that is, after all, an industrial version of the law of evolution: adapt or die.
This, for Schmidt and Frank, is one of the central themes of the Silurian hypothesis. If we can reflect on the possibility that we may not be the first Earthlings to produce a technologically advanced civilization, perhaps we can better appreciate the precariousness of our current situation.
“The idea about our place in the Universe has been this progressive distancing of ourselves. It’s like a gradual withdrawal from a totally self-centered view, and the Silurian hypothesis is really just an extra way of doing it. We need to be objective and open to all types of possibilities that the Universe really has to offer us”, said Schmidt.
