Ashton Kutcher: Good Genes or Good Docs?!

Ashton Kutcher's chiseled good looks haven't changed since the "'70s!"

Here's a 21-year-old version of the "Dude, Where's My Car" actor at an awards show back in 1999 (left) and 16 years later ... the "Two and a Half Men" star -- who celebrated his 37th birthday this weekend -- at a movie premiere earlier this month (right).