If You Are a “Doctor Who” Fan Then You Know About the Silurians

In the seventh season of the British science fiction television drama “Doctor Who,” the writers introduced a bipedal intelligent reptilian species they called Silurians.

Named after a period in early Earth history spanning 444 to 419 million years ago, the Silurian Era, unbeknownst to the writers of Doctor Who, had no reptiles, or at least there is no fossil record of them. The dominant species of the time were arthropods (think lobsters and crabs, insects and spiders), molluscs (think octopus, squid and snails), and the first fishes. So no bipedal intelligent reptilian existed in the Silurian. This was a period in Earth’s history that indicates much warmer land and sea temperatures, and carbon dioxide (CO2) atmospheric levels that reached 4,500 parts per million, more than ten times the number that is of such great concern to climatologists presently.

The Silurian geological record indicates repeated extinction events, little in the way of land ice anywhere, and the forming of a supercontinent near the equator when continental plates converged.

Think about what evolution working through 25 million years might have produced. We are talking about a period 100 times greater than our species’ existence on Earth. So could in that amount of time another intelligent species have evolved in the oceans or on land here on Earth and yet we have no record of its existence after 419 million years?

Think about it. Modern industrial civilization is 150 years old. The period we live in has recently been named the Anthropocene indicating the era where evidence of human existence is now in the geological record. And what is that evidence? It isn’t the monuments, bridges, buildings, and other accoutrements of civilization but rather, microscopic pieces of plastic embedded in sediments being laid down in today’s oceans, lakes, and rivers which will someday turn into sedimentary rock, and a bit of radioactivity in those rocks should our existence be wiped out in a thermonuclear war. Will this evidence persist for 20, 50, or even 100 million years? Will anything remain in 400 million years that indicates there was an advanced civilization, or will there only be fossilized bones?

Back in the Silurian, or even more recently in any other geological period of time, would we see evidence of sentience, civilization or advanced technology left by an intelligent lobster or octopus? Would we even know where and what to look for when seeking evidence of sentience? Would we only find what we see in the geological record, fossil imprints?

The Silurian Hypothesis

The Silurian Hypothesis is not a work of science fiction. It was proposed by two scientists: Gavin Schmidt, a NASA climatologist studying exoplanets, and Adam Frank, an astrophysicist from the University of Rochester.

Schmidt’s work on exoplanets looks at the gaseous composition and thermodynamics within their atmospheres. The presence of some gasses might indicate the existence of an advanced civilization. A warming of the atmosphere might do so as well just as we are seeing today with anthropogenic global warming.

Schmidt argued that a hyperthermal jump in atmospheric temperature as well as the presence of gasses produced by industrial activity might be the only evidence we ever find to indicate the existence of an intelligent alien species elsewhere. But why look elsewhere when he could look here on Earth and seek evidence of a past intelligent civilization?

The hypothesis chose to look at one specific period in Earth’s geological record, only 55 million years ago, called the Paleocene–Eocene Thermal Maximum when atmospheric temperatures increased from 5 to 8 Celsius (9 to 14 Fahrenheit) degrees. This warming coincides with a period when CO2 atmospheric levels were much higher confirmed by the geological record. Could a sentient, technically advanced species of Silurians be responsible for the evidence? Or maybe it was just a piece of space rock or a massive volcanic eruption that could explain it away.

Anything short-lived such as our present industrial civilization would likely be undetectable in the geological record seen 20 million years or more in the future. The Earth’s shifting continents, weathering, and other dynamics would bury the evidence. An ancient civilization would be unremembered and unknown. Both Schmidt and Frank noted that we haven’t the tools to detect past civilizations that far back in time. At best we can find the bones of our ancestors at sites in Africa. As for other sentient species that create an advanced civilization, take the octopus for example, what kind of constructs would we see in the geological record to tell us that story? Schmidt and Frank believe that it may be the fate of all intelligent species that build a civilization, that their rise and fall will in the end be undetected. There will be no legacy to study even as a civilization like ours studies to uncover the mysteries of a Universe in which we are just a voyager passing.