Why are testicles on the outside of the male body? what is the evolutionary advantage of this? Wouldn't they be better off inside where they would be more protected?

the testicles are temp sensitive, that`s why the scrotum material and hairs are designed in such a way as to maintain a constant and even temp, the scrotum skin is special in that it can Move, and either bring the testes closer to the body (in cold) or lower them for max surface area evaporation (when hot).

 

basicly it`s a self regulating incubator for spermatazoa production

Spermiogenesis, the process of producing sperm, is more efficient at temperatures below the body's core temperature.

ahh that explains a bit

 

edit: any mods out there want to close this before it gets ruined by some joker

Good point! closed