Something I Don't Want to Know More About
The Island of Menstruating Men by Ian Hogbin. It's a book that we're either digitizing or cataloging (I'm not sure which) at work.
In parts of New Guinea, there's a belief that men, as well as women, have to shed blood from the genital region regularly.
After trying to look it up at Wikipedia and reading one of the relevant articles, I no longer regard circumcision opponents as completely insane, merely mostly insane. (Warning: The image in the Wikipedia article is NSFW and, for that matter, not safe for lunch.)