This is, perhaps, the strongest introduction I've ever read to an academic paper:

"In the tropical forests of New Guinea, the Etoro believe that for a boy to achieve manhood he must ingest the semen of his elders. This is accomplished through ritualized rites of passage that require young male initiates to fellate a senior member (Herdt 1984/1993; Kelley 1980). In contrast, the nearby Kaluli maintain that male initiation is only properly done by ritually delivering the semen through the initiate’s anus,not his mouth. The Etoro revile these Kaluli practices, finding them disgusting. "