We may not be not the universe's first advanced civilization.
University of Rochester astrophysicist Adam Frank is the co-author of a new paper that puts some numbers on how likely it is that humans are unique. His conclusion? Other intelligent life has very likely come before us. How often?
We discuss how Frank modified the famous "Drake Equation" of 1961, and why it's so likely that other intelligent life is either out there -- or has been out there, at one time or another.