Silurian Hypothesis

Let's have some fun today and do some speculation, talk science and science fiction, and discuss the possibility of other intelligent life out there in the vast expanses of outer space...

To start this wild and fun thought experiment we're going to make the assumption that we, human beings, are quite successful in terms of evolutionary success. What's made us so successful, and placed us on top of every food-chain on the planet, is undoubtedly our intelligence, our complex brains. You see, phenomena that are successful in evolution tend to be repeated many times; they evolve time and time again and independently of previous iterations. The concept of flight, for example, has evolved in insects, birds and reptiles, in completely different branches on the tree of life. So has sight, with many different kinds of eyes. Or slime; nature has deemed it useful to put it in many mouths, on many skins and under a snail's foot.

Building on that idea of success repeating in evolution, the Silurian Hypothesis asks the question if intelligent life could have evolved right here on earth, many millions of years before our earliest ancestors stood upright. This is not that far-fetched if you ask me. Look around at what we've accomplished in only a few thousand years. And then imagine that, if we become extinct, all we've build, the factories, the machines, the houses, the streets, all of it, will disappear in just a few millennia, leaving next to nothing to uncover for any alien visitors in the very far future. Could not the same have happened to a civilization of intelligent beings that went extinct a couple of hundred million years ago? You see, fossilization is quite rare, and earth is a planet that's in constant motion, due to climate change, tectonic activity and so on.

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. After a great time span, the researchers concluded, contemporary humans would be more likely to find indirect evidence such as rapid changes in temperature or climate (as occurred during the Paleocene–Eocene Thermal Maximum ~55 million years ago); evidence of tapping geothermal power sources; or anomalies in sediment such as their chemical composition (e.g., evidence of artificial fertilizers) or isotope ratios (e.g., there is no naturally occurring plutonium-244 outside a supernova, so evidence of this isotope could indicate a technologically advanced civilization).
_{source: Wikipedia}

The hypothesis is named after the Silurians, a race of reptilian humanoids in the long-running British science fiction television series Doctor Who. The first Silurians introduced, in Doctor Who in the 1970 serial Doctor Who and the Silurians, are depicted as prehistoric and scientifically advanced sentient humanoids who predate the dawn of man. This hypothesis was introduced by Adam Frank, an astrophysicist at the University of Rochester, and Gavin Schmidt, director of the Goddard Institute for Space Studies, in a 2018 paper. They argue that there was enough fossil carbon on the planet to fuel a civilization comparable with our own as early as 350 million years ago. They also speculate that such a civilization could have left the planet and may have left artifacts on other celestial bodies in our solar system, like the Moon or Mars, where evidence of such artifacts would be easier to find than on Earth, where erosion and tectonic activity would erase much of it.

Finding out, and thinking about preceding intelligent civilizations on earth could also teach us a lot about the probability of intelligent life evolving elsewhere in the universe. It's a fascinating subject, if you ask me. So watch the below linked video from Anton Petrov; he's a great resource for anyone who has an interest in anything relating to the universe and our endeavors to learn more about it.

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