There was a moment in the not-so-distant past when we learned what drove the dinosaurs extinct — and that discovery, made during the Cold War, may have helped save humans from the same fate. David Sepkoski, Thomas M. Siebel Chair in History of Science at the University of Illinois and author of Catastrophic Thinking: Extinction and the Value of Diversity. Alec Nevala-Lee, novelist, critic, and biographer and author of the forthcoming book Collisions: A Physicist's Journey from Hiroshima to the Death of the Dinosaurs.