I recommend watching the above video of a presentation by Mark Passio on sexual repression in societies around the world today. Based on my own research, I can tell you that he’s very, very close to the truth. He doesn’t talk about the origins of sexual repression, but does mention its purpose, which quickly becomes obvious once you understand what’s going on. For the origins you can read my post “Sexual Suppression and Repression I: Definition and Origin”.