Villain That Nearly Killed All Life on Earth Is ... Tiny

Name your favorite culprit for the mass extinction that wiped out nearly every life form on Earth 250 million years ago. A spectacular asteroid, perhaps? Massive volcanic eruptions? Both are popular theories, but a new study encourages sleuths of the Permian era to think much, much smaller, reports the Guardian. As in microscopically smaller. MIT scientists propose that a microbe called Methanosarcina proliferated in the oceans, disgorging huge amounts of methane into the atmosphere and making life in the water and on land all but impossible for most species.

"In short, a microbial innovation may have tipped over the balance to cause the Great Dying," explains Ars Technica. So what caused the microbes to explode in numbers? That's where those volcanoes may have played a role, though a lesser one than has been long surmised. Scientists think a flurry of eruptions in Siberia resulted in a huge increase in nickel, upon which Methanosarcina happens to thrive. An estimated 90% of marine species were wiped out in the changed atmosphere, along with 70% of land vertebrates. It took millions of years for both to recover, with the first dinosaurs showing up about 20 million years later, reports Reuters. (Scientists recently determined that the Permian mass extinction happened really, really quickly.)