Robert Downey Jr. getting older or younger???

Robert Downey Jr.

GOOD GENES OR

GOOD DOCS?

Robert Downey Jr.'s good looks have been resurrected!

Here's a 21-year-old version of the "Back To School" stud leaving a movie premiere in New York City back in 1986 (left) and 29 years later ... the "Iron Man" -- who turned the big 50  -- at an awards show earlier this year (right).

Robert Downey Jr.

•  Good Genes
•  Good Docs

It's a mystery dear Watson!

The question is.