Climatologist Gavin Schmidt of NASA's Goddard Institute for Space Research and astrophysicist Adam Frank of the University of Rochester put forward the "Silurian hypothesis" according to which the ancient advanced civilizations of the Earth should have left traces of their stay on the planet. The article was published in the International Journal of Astrobiology.
The researchers named their hypothesis after the Silurians - intelligent reptiles from the British science fiction series Doctor Who, who, according to the plot, were the first evolved creatures on Earth.
Scientists did not try to present accurate evidence of the existence of other intelligent life forms before humanity, but only to show that such a possibility exists. The Silurian Hypothesis is a thought experiment that should help answer the question of whether it is possible to find evidence of the existence of advanced civilizations that died millions or billions of years ago.
According to Schmidt and Frank, humanity has entered the era of the Anthropocene, when the biosphere is significantly influenced by civilization. Thus, the activities of people are "recorded" in geological deposits, and these traces can be found and studied by researchers of the distant future.
However, in this case, according to scientists, a paradox arises. A civilization that can survive for a long time must create a sustainable economy that will not overload natural ecosystems. On the contrary, a noticeable geological footprint can be left by those civilizations that quickly reached the peak of development and fell into decay due to the depletion of resources and global changes in the biosphere.
Thus, the "Silurian hypothesis" suggests that geological footprints such as those that humanity is leaving now could be found, since it is far from embarking on a sustainable path. Such evidence includes, for example, mass extinctions of animals, plastic debris, synthetic pollutants and steroids that can persist for millions of years, as well as fluctuations in the ratio of different isotopes, indicating an increase in atmospheric carbon from the burning of fossil fuels.
At the same time, the creation of synthetic substances cannot be regarded as a common feature of all intelligent civilizations. The rest of the tracks can be attributed to natural causes, such as increased volcanic activity and other tectonic processes, an asteroid fall or fluctuations in the global carbon cycle. Therefore, scientists come to the conclusion that only more thorough studies than those carried out so far can detect traces, if any.
