Ray Romano shared an interesting theory about evolution and growing old, on 'Late Show With David Letterman' (Weeknights, 12:37AM ET on CBS).

Romano told host David Letterman about how a recent game of hoops with his kid resulted in him "taking a shot to the groin."

As Letterman grimaced and the men in the audience groaned in sympathy, Romano came out with one surprising benefit to getting older. Having said that a shot in the groin is the worst pain imaginable for a man, he said that this one, well, "It didn't hurt as much."

And here's Romano's explanation why: Evolution. Yep, the 50-something actor reckons that when a guy gets hit "down there" in his 20s or 30s the ensuing agony is nature's way of telling him to be careful with his man parts because he and the species needs them.

However, once you reach a certain age, he said, they become a bit redundant. To gales of laughter from Letterman, he concluded: "When you're older, they're kind of like tonsils."