John O'Hurley: Good Genes or Good Docs?

John O'Hurley's good looks are the best in show!

Here's a 43-year-old version of the sexy silver fox livin' it up in Puerto Rico back in 1997 (left) and 19 years later ... the host of The National Dog Show -- a Thanksgiving Day staple -- in Hollywood last month (right).

Doggone handsome.

The question is...