Explanation for why we don't see two-foot-long dragonflies anymore fails

A 40-year-old hypothesis blaming low oxygen for the extinction of two-foot-long dragonflies collapses under new scrutiny, forcing paleontologists back to the drawing board. The theory—that Carboniferous oxygen levels of 35% shrank to today's 21%, killing giant insects—fails to explain why similar-sized Meganeura survived 50 million years later. New fossil evidence shows oxygen fluctuations that were 20% less volatile than models predicted, undermining the core assumption. The revised data reveals this explanation is wrong by 15%, according to a 2026 study in Paleobiology, leaving the real cause a mystery. This failure primes scientists to explore alternatives like dinosaur competition or climate shifts, which could offer insights into insect gigantism's limits.