Lycan

Back when food wasn't as 'safe' as now. People would ingest fungus and what not on their grains. Gave them all sorts of visions etc. Back in the day of no television their imaginations were fertile grounds for lots of things. Some people believed with the moon that they went wolf like. Wolves were fearsome things and when an oppressed peasant got the notion then he would believe with the help of ergot or whatever that became wolf. As things go, the ideas flourished and now we have movies and all sorts of things. Even Indians believed in skin walkers.