LIFE ON THE EDGE: SURVIVING EARTH'S GREATEST EXTINCTIONS

Two hundred million years before dinosaurs vanished, something worse happened. The Permian extinction. Siberian volcanoes erupted for millennia. Colossal winds of lava and toxic gas. The oceans turned deadly. Ninety-six percent of marine life disappeared. Scientists call it the Great Extinction. Yet even this was not the worst crisis life ever faced. Something more extreme was coming.