Reese Witherspoon GOOD GENES OR GOOD DOCS?

3/27/2016 12:10 AM PDT BY TMZ STAFF

0322_reese_witherspoon_genes_docs_launchIt's wild how good Reese Witherspoon looks.

Here’s an18-year-old version of the "Legally Blonde" babe at a movie premiere in Hollywood (left) and 22 years later ... the Oscar winner – who celebrated her 40th birthday earlier this week – on the red carpet at the Academy Awards last month (right).

Bend and snap!

The question is…