Kris Jenner -- Good Genes or Good Docs?

Good luck keeping up with Kris Jenner's good looks!

Here's a 35-year-old version of the "Keeping Up with the Kardashians" star at her Los Angeles home back in 1991 (left) and 26 years later ... the momager of six -- who is celebrating her 62nd birthday Sunday -- at an auction in Los Angeles early last month (right).

"Okurrr!"

The question is ...