Tracy Morgan -- Good Genes or Good Docs?!

Tracy Morgan has been looking good from his first Sunday to this Sunday!

Here is a 32-year-old "30 Rock" comedian rockin' a stache at the premiere of Comedy Central's "Crank Yankers" in New York City back in 2001 (left).

And, 18 years later ... the now 51-year-old father of four -- who is celebrating his birthday today -- supporting his fellow "Saturday Night Live" alum, Eddie Murphy, at the premiere for his Netflix film, "Dolemite Is My Name," in Los Angeles last week (right).

If he keeps this up, he will definitely be the last O.G.

The question is ...