Circumcision presumes to improve upon evolution, yet without evidence and for nothing but cultural reasons.
The genitals evolved on humans and other animals over millions of years, and just a few millennia ago some tribes decided that they should be cut up.
You don't need your appendix either as evolution is far from perfect. - Removal of the foreskin has no deleterious effects, and has small but proven medical benefits.
Evolution produces imperfect designs and there's no reason why we wouldn't be able to modify humans to improve the design.