Two astrophysicists thought, “Hey, why not rethink the theories of Doctor Who and publish a paper on it?” Okay, this is not the entire story behind the recently published paper in the International Journal of Astrobiology. Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, and Adam Frank, an astrophysicist from the University of Rochester, conducted a thought experiment and raised several questions about the possibility of civilization as intelligent as humans that lived long before human evolution. For the study, the authors looked at the possible footprints of Anthropoce, the term that is now used to signify current geological age where human activities have huge influence on the environment and climate.

If one looks at the timeline, the Big Bang, took place some 13 billion years ago. The solar system existed at around 4.5 billion years ago and the first life form was developed around 3.8 billion years ago. Moreover, humans developed industrialization just about 300 years ago. Thus, researchers strongly believe that a civilization could rise and fall before humans could even see a daylight. According to a rendition of Doctor Who, a British science-fiction television program, civilization of reptiles called Silurian evolved before humans, and inspired from this science-fiction theory, scientists published a paper titled, “Silurian hypothesis” that questioned what exactly happened before brainy humans showed up on the earth.

While speaking about his paper, Frank said, “I do not believe that there was a civilization before humans, nor say that there was a well-developed dinosaur civilization; however, I believe that the whole point of science is to ask unasked questions and see where they lead. That’s what this study is all about.”

According to him, artifacts of any species are hard to find after billion years as very small fraction of life gets fossilized. For instance, dinosaurs wandered on the earth about 200 million years ago and only thousands of complete fossils are recovered. Furthermore, the oldest human fossil recovered is approximately 300,000 years old, which suggests that even human species will not appear in the fossil records after million years in future. Therefore, the two scientists thought about the signs that our civilization would left behind after a passage of aeon, and based on that, one can search for the similar signs of the pre-human civilization.

According to the pair, evidences of the pre-human civilization might include presence of plastic in the oceans or distribution of fertilizers in agriculture. Furthermore, the detailed study and evidences might suggest that multiple cultures on a single planet are fueled by remains of the predecessors. Furthermore, the civilization on the verge of extinction might trigger the geological conditions required for the formation of oil, gas, and other natural resources, which future civilizations could use for their industrialization. From the beginning of time to the advancement of one culture, and from discoveries of human history to the predictions about the human civilization, the thought experiment touches all aspects of astrophysics. And, in a way, the study proves that a demise of one civilization can sow seeds for new culture in future.