“Whether the apparent cycle reflects a genuine feature of Earth’s history remains an open question.”
An NYU geologist ran 89 geological events across 260 million years and found a 27.5 million year beat. The paper itself lists the problem: the record is full of holes, ancient dates get fuzzier the further back you go, and statistics will hand you a cycle in noise if you ask it politely. Periodicity claims in the fossil record have been made and withdrawn since the 1980s. The proposed mechanisms include dark matter, which is where these arguments usually end up.