Those are interesting questions. Some forms of SI were sanctioned in earlier periods of history. Like self-flaggelation for penance during medieval times. And blood letting used to be considered cleansing, although usually the doctor would do it. I'm sure that people have always sometimes thrown themselves into their physical labors and occasionally overdone it when they felt a need to work off some emotions, but didn't have an outlet for talking about it. I bet that while methods and perceptions and interpretations have probably varied a lot, there have probably been people who felt better through pain of some kind.

Rap