I came across this info in my reading of ancient Roman times. Apparently some ancient authors (Pliny and Plato) spoke of this.

The legend of the werewolves comes from the practice of ancient secret cults which would live in the wilderness. They would capture humans and eat their flesh as part of their rituals. But if the diner accidentally ate some of the human entrails, they were forced to live among the packs of wild wolves. They had to refrain from eating human flesh for nine years before they would be turned back to human form and allowed to return.

Wild, huh?