Billy Bob Thornton -- Good Genes or Good Docs?

Billy Bob Thornton's good looks are award-winning!

Here's a 42-year-old version of the "Fargo" star making an appearance on a talk show in New York City back in 1997 (left) and 21 years later ... the now 63-year-old actor was striking a pose at a film festival in Napa in November (right).

No bad news here.

The question is ...