A little over 250 million years ago, our planet experienced a mass extinction the likes of which have never been seen before or since. About 90% of all species were suddenly wiped out. And new study suggests it wasn't caused by an asteroid or super-volcano — but rather methane-spewing microbes.
About 250 million years ago, the world suffered through an extinction event that makes the death of the dinosaurs look like a minor hiccup by comparison. And now we have our best understanding yet of what caused the Great Dying.