Justin Long -- Good Genes Or Good Docs?!

Justin Long's looks are nothing to dodge!

Here is a 23-year-old version of the actor and comedian sporting a smooth shave at a benefit in New York City back in 2001 (left). This was the same year he was cast in two break-out film roles, "Happy Campers" and "Jeepers Creepers."

And, 21 years later ... the handsome "Dodgeball: A True Underdog Story" star -- and father of two -- recently rocked a pretty sweet 'stache while hanging around San Diego, California (right).

He certainly isn't looking long in the tooth!

The question is ...