The Silurian Hypothesis
Could ancient aliens have built an advanced civilization before our own? Will future civilizations ever find traces of humans?
If an advanced civilization had existed on Earth many millions of years prior to our own era, what traces would it have left behind and would they be detectable today?
What would be the geological fingerprint of the Anthropocene, and would it differ compared to other known events in the geological record? Would it be possible to distinguish an industrial cause from a climate event?
Modern humans have been around for approximately 300 000 years, but life has existed on this planet for 3,5 billion years. That leaves 3 499 700 000 pre-human years unaccounted for — more than enough time for the rise and fall of not one, but several pre-human industrial civilizations.
The Silurian Hypothesis speculates that it’s possible for civilizations to have gone completely extinct and that their relics have been buried for a long time. Could we find evidence that ancient aliens built an industrial civilization long before our own?
It’s not as absurd as it sounds. On the geologic time scale, we’ve only been here for an instant, and industrial civilization has only existed for a fraction of that instant. If humans went extinct tomorrow, the relics of our society wouldn’t last very long.
Homo sapiens means “wise man” in Latin and as far as we understand evolution, humans have existed for roughly 300 000 years. 1% of that time we proudly refer to as “history” and during a fraction of the “history” we have possessed the technology to leave the planet but also to destroy ourselves and wipe out other species.
Our impact is so great and varied that we have introduced a new geological time period in Earth’s history. Its name is the Anthropocene — the human epoch. But what traces of human civilization would future scientists find from the Anthropocene epoch?
Recent research from NASA suggests that humans will not leave fossil traces in the same way as dinosaurs and for multiple reasons. The remains of most people are cremated or buried in soil where the bones are decomposed. The research even suggests that there will be basically no human fossils after a few million years.
Other research material concludes that the PETM periods (like the one 56 million yrs ago) would leave similar traces as a long gone civilization, for example higher levels of coal and oxygen. Andre Norton’s “The Time Traders” discusses the idea that most physical evidence of ancient advanced civilizations on Earth could be removed by glaciers, volcanic eruptions and decay.
Would it be possible that future intelligent species will walk the Earth without finding traces of us? If so, would it be possible that we (humans) are not the first civilization with comparable intelligence?
The Silurian hypothesis is a thought experiment by Adam Frank and Gavin Schmidt that assesses the modern science ability to detect evidence of a prior high technological civilization that existed millions of years ago. It’s a nerdy reference to Doctor Who, which posits a race of intelligent reptiles that predate humans.
Their conclusion is that our probable impact on the planet will be palpable but in many ways hard to distinguish from other events in the geological record. The chances of finding direct evidence from a civilization such as ours are small but there may be indirect evidence by anomalies in the sediments such as microplastics and nuclear waste.
But future races do not necessarily produce the same type of waste or leave the same traces as humans of today. Same thing if we look back in time. Ancient civilizations were not humans and they did most likely not use plastics or master nuclear technology. Hence we would have to look for something else.
The late astronomer Peter Nilson speculates that “humans” and similar intelligent species may exist many times after our current civilization has gone. Some will be stuck on stone age level and some will travel between the stars. But, if there is enough time between the “civilizations” there won’t be any traces left.
Mountains grow and are then grinded away, oceans flood the continents and comets and asteroids create global destruction, the ground is worn down by rain, frost and wind, continents drift around and are pushed down on the seabed and melted into the core and pushed back to the surface again.
According to Peter Nilson, time will wipe out all (or most?) of our traces. Some new civilizations or races will find traces of previous ones and some will not find anything and hence not know anything about the existence of humans.
Anything organic would decay and become part of the soil, and durable materials would slowly weather away. Glass and ceramic would become sand; steel girders would become unusual ore deposits. Satellites would deorbit and burn up in the atmosphere. Shipwrecks on the ocean floor would slowly dissolve.
Is it reasonable to believe that “humanoids” will come and go over the coming hundreds of millions or even billions of years? And if so, can civilizations re-generate elsewhere in the universe and wouldn’t this increase the chance for intelligent life in the universe?
One could speculate about the need for “intelligent life” — is intelligence really favorable from an evolutionary point of view? Evolution going forward is to better fit your niche and hence not needed in a stable environment, only during rapid changes such as for example climate changes.
This view suggests that it may take a long time for a new intelligent race to come forward and for that reason humans may be the first, last and only intelligent high technological species that will ever evolve on Earth. This means that there will be no one looking for our fossils regardless of whether they are here or not.
