Guests: S. Jay Olshansky and Bruce Carnes.

At the start of the last century, the average life span was just 45 years. Today the average for women is 79 and for men 72. What brought about this change? Can we expect even greater gains in human longevity? Today on Focus, we'll talk with researchers S. Jay Olshansky and Bruce Carnes on how to live as long as possible.