Schmidt and Frank (2019) propose the "Silurian Hypothesis," which states that an industrial civilization may have existed prior to modern civilization, likely between the Devonian and Pliocene (~5 - 420 million years ago). They propose several geochemical and paleontological tests that could provide evidence for the hypothesis, though whether such a civilization would even be detectable in the geologic record remains uncertain.
This question will resolve yes if at least three papers in high-impact peer-reviewed journals (including the Astrophysical Journal, Science, Astrobiology, and Nature family of journals) present evidence supporting this hypothesis by Dec. 31, 2050.
1,000According to wikipedia this is more of a thought experiment to discuss whether a human-like civilization could be detected in the geological record than a hypothesis. A yes resolution seems highly unlikely.
@VAPOR I'd recommend reading Schmidt and Frank (2019) for an overview of some possible evidence [link: https://www.cambridge.org/core/services/aop-cambridge-core/content/view/77818514AA6907750B8F4339F7C70EC6/S1473550418000095a.pdf/silurian_hypothesis_would_it_be_possible_to_detect_an_industrial_civilization_in_the_geological_record.pdf]. Evidence could include the presence of radiogenic isotopes or CFCs within ocean sediments that are not produced by natural processes.