Throughout human history, people have warned that the end of the world is coming. If it does, it won’t really be all that unique. You see, the world has already ended five times. Life on earth has been broiled, frozen, gassed, smothered, and asteroided out of existence. And scientists believe that those previous mass extinctions can teach us something about the one happening right now. Monday, science writer Peter Brannen joins us to explore the Earth’s past dead ends and what they mean for the future.