If an industrialized civilization had existed on Earth millions of years before our era, what traces would it have left, and could they be detectable today? That is the astounding premise that led Adam Frank, an astrophysicist at the University of Rochester, and Gavin Schmidt, director of NASA’s Goddard Institute, to write an article in 2018 proposing what is known as the Silurian Hypothesis.

The term Silurian Hypothesis was inspired by an episode of the TV series Doctor Who, featuring intelligent reptiles, and the study was published in the International Journal of Astrobiology.

In the article, both scientists wondered how the existence of a civilization preceding ours by several million years could be detected. Fossilization is a relatively rare process; otherwise, we would be finding dinosaur fossils every day. Combined with the fact that the Earth’s crust is renewed and modified due to tectonic activity, and that very little of the current surface was exposed before the Quaternary, it becomes very difficult to find physical traces or direct remains of a possible civilization from such ancient times.

Therefore, their conclusion is that we would most likely encounter indirect evidence, such as anomalies in the chemical composition or isotopic ratios in sedimentary layers, due to the use of fossil fuels and nitrogen-based fertilizers, for example, which could be detectable in the fossil record for eons.

As for objects that could indicate possible evidence of past civilizations, they include plastic waste and nuclear waste buried in the depths of the subsoil or on the ocean floor, making them very difficult to find. It would be simpler if these civilizations had ventured into space and left artifacts on the Moon or Mars, where they would be easier to find due to less erosion and tectonic activity.

Of course, both authors are aware that what they are proposing is highly improbable:

We are aware that suggesting the possibility of a previous industrial civilization as a driver of events in the geological record could lead to quite unlimited speculation. One could adjust any observation to an imagined civilization in ways that would be essentially unfalsifiable. Therefore, one must be careful not to postulate such a cause until positive evidence is available. The Silurian hypothesis cannot be considered probable simply because no other valid idea is presented.

Frank and Schmidt conclude their article by stating:

Perhaps unusually, the authors of this article are not convinced of the accuracy of the proposed hypothesis. If true, it would have profound implications not only for astrobiology. However, most readers do not need to be told that deciding on the truth or falsehood of an idea based on the consequences of it being true is always a bad idea. Although we doubt very much that there was a previous industrial civilization, the act of formally posing the question and explicitly articulating how evidence of such a civilization could be raises its own useful questions related to both astrobiology and anthropocenic studies. Therefore, we hope that this document serves as motivation to improve the limitations of the hypothesis so that in the future, we may be better equipped to answer our question in the title.

As an experiment, it is an interesting hypothesis, but only that, as there is currently no evidence of Silurians or other intelligent beings predating humans on planet Earth.

This article was first published on our Spanish Edition on June 19, 2019. Puedes leer la versión en español en La Hipótesis Siluriana: ¿sería posible detectar una civilización avanzada en el registro geológico?


The Silurian Hypothesis: Would it be possible to detectó an industrial civilization in the geológica record?, Gavin A.Schmidt and Adam Frank, International Journal of Astrobiology, doi: 10.1017/S1473550418000095 / Was There a Civilization On Earth Before Humans? (Adam Frank)

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