The Great Filter hypothesis says we’re alone in the universe because the process of evolution contains some filter that prevents life from spreading into the universe. Have we passed it or is it in our future? Humanity’s survival may depend on the answer. (Original score by Point Lobo.)

Interviewees: Robin Hanson, George Mason University economist (creator of the Great Filter hypothesis); Toby Ord, Oxford University philosopher; Donald Brownlee, University of Washington astrobiologist (co-creator of the Rare Earth hypothesis); Phoebe Cohen, Williams College paleontologist.