There's also horizontal "translation" -- as a child I had a book which was plainly European fairy tales translated linguistically and culturally into India (e.g. a princess whose wicked stepmother forced her to separate rice and sand).
I wonder how many stories suffer "mutations" that break them from their previous incarnations. The article mentions "The Smith and The Devil", and speculates that metal-working technology would have been around at the time of its origin, but I'm not sure if that's any more likely than the profession of the protagonist changing over time.<p>At the very least, in Russia there are many tales of Ivan outwitting the Devil, regardless of his profession. Maybe that's just a horizontal transfer and the story taking advantage of a previously unoccupied memetic niche...