PETER SAGAL, HOST:
In the fall of last year, we reached a milestone - our 1,000th show. It's amazing we ever made it this far.
BILL KURTIS: It feels like it's just been 970 or so.
SAGAL: To mark the occasion, we went back to Salt Lake City, where we did our first-ever show in front of a live audience. And there, we talked to a remarkable woman, a professor of biology at the University of Utah.