I must admit that I had never heard of the Silurian Hypothesis until I recently read an article which referred to it. I decided to look it up and was fascinated by the possibility it presents. Again, I have never seen, or heard, anything like it, despite being an avid student of history. I hope you enjoy it as much as I did and, perhaps, it will make you think a little harder about the origins of homo sapiens.
The Silurian hypothesis is a thought experiment, which assesses modern science’s ability to detect evidence of a prior advanced civilization, perhaps several million years ago. The most probable clues for such a civilization could be carbon levels, radioactive elements or temperature variations. (The name “Silurian” derives from the BBC science fiction series Doctor Who.)
Astrophysicists Adam Frank and Gavin Schmidt proposed the “Silurian Hypothesis” in a 2018 paper, exploring the possibility of detecting an advanced civilization that existed before humans in the geological record. They argued that there has been sufficient fossil carbon to fuel an industrial civilization at least since the Carboniferous Period (~350 million years ago). However, finding direct evidence, such as technological artifacts, is unlikely, due to the rarity of fossilization and Earth’s exposed surface. Instead, they argued, researchers might find indirect evidence, such as climate changes, anomalies in sediment, or traces of nuclear waste.
However, they also wrote: “While we strongly doubt that any previous industrial civilization existed before our own, asking 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 studies of homo sapiens (us).”
According to Frank and Schmidt, since fossilization is relatively rare and little of Earth’s exposed surface is from before the Quaternary time period (~2.5 million years ago), there is low probability of finding direct evidence of such a civilization, such as technological artifacts.
I should add here that there is also the phenomenon of continental drift to take into consideration (picture above): Those movements could easily have taken evidence of previous civilizations below the current sea levels. (Remember 70% of the Earth’s surface is covered by water).
Frank and Schmidt speculate such a civilization could have gone to space and left artifacts on other celestial bodies, such as the Moon and Mars. Evidence for artifacts on these two worlds would be easier to find than on Earth, where erosion and tectonic activity would erase much of it.
Frank first approached Schmidt to discuss how to detect alien civilizations via their potential impact upon climate through the study of ice cores and tree rings. They both realized that the hypothesis could be expanded and applied to Earth and humanity since humans have been in their current form for only the past 300,000 years, and have had sophisticated technology for only the last few centuries.
The Silurians on Doctor Who are a race of reptilian humanoids from Earth’s past, made their first appearance in the show in 1970. Frank and Schmidt cite Inherit the Stars, a 1977 novel by J. P. Hogan as containing a similar hypothesis, but also say they were surprised by how rarely the concept was explored in science fiction. Some attempts have been made, but they are few and far between. Examples would be:
In Larry Niven‘s 1980 short story “The Green Marauder”, an alien over 700 million years old (due to relativistic travel) tells a human about the last time it visited Earth, and the hopeless plea from the Earth’s civilization for help against the growing environmental threat of chlorophyll.
The Star Trek Voyager 1997 episode “Distant Origin” has the crew encounter the Voth, a spacefaring race that appear to have evolved on Earth from dinosaurs. When discussing this theory with a Voth scientist, Chakotay speculates that their ancestors evolved on an isolated continent that was destroyed by cataclysm, with all traces buried under oceans or kilometers of rock.
Crazy ideas, perhaps but, given the fact that our current “civilization” has existed for less than the blink of an eye in the history of planet Earth, they are certainly not outside the realms of possibility. Perhaps we should spend more time and effort investigating the Silurian Hypothesis, we might learn something about our own fragile existence. It is certainly intriguing to contemplate.
