The worst mass extinction in known history happened 250 million years ago, wiping out an astonishing 96% of all marine life. Scientists have offered many theories on how this could have happened, from meteors to volcanoes--but a research team may have finally cracked the code, and it doesn't bode well for our own future. Charlie brings in a paper that takes a grim dive into the world's most lethal time period. Read the paper and news articles here.