Kim Kardashian's Big Ass: Good Genes or Good Docs?

Kim Kardashian's backside is a growing sensation.

Here's a 26-year-old version of the budding sex-tape tush in a polyester little black dress back in 2006 (left) and 9 years later -- a 34-year-old version of the reality rump in a pair of industrial strength mom jeans arriving at an L.A. studio Monday (right).