The Silurian hypothesis is a thought experiment,[1] which assesses modern science's ability to detect evidence of a prior advanced civilization, perhaps several million years ago.
Astrophysicists Adam Frank and Gavin Schmidt proposed the "Silurian Hypothesis" in a 2018 paper,[2] exploring the possibility of detecting an advanced civilization before humans in the geological record.
[1] 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.
[4] Frank first approached Schmidt to discuss how to detect alien civilizations via their potential impact upon climate through the study of ice cores and tree rings.
When discussing this theory with a Voth scientist, Chakotay speculates that their ancestors evolved on an isolated continent that was destroyed by cataclysm, with all traces buried under oceans or kilometers of rock.