The paper can be found here:<p><a href="https://www.researchgate.net/publication/381041896_The_cryptoterrestrial_hypothesis_A_case_for_scientific_openness_to_a_concealed_earthly_explanation_for_Unidentified_Anomalous_Phenomena" rel="nofollow">https://www.researchgate.net/publication/381041896_The_crypt...</a><p>Without the Harvard affiliation I don't think this would make news. It's not been peer reviewed and I don't think the first author is (or claims to be) an expert on the relevant topics. (Hard to say what the relevant topics would be, maybe archeology or geology?)
> This paper has made the case for taking seriously the CTH [“cryptoterrestrial” hypothesis] as a potential explanation for UAP, while noting that it probably ranks lower than other hypotheses, such as the extraterrestrial explanation, although such calculations are hard to quantify.<p>Even the paper admits it's reaching.