JP often refers to the "Kuzari principle", first mentioned by R. Yehuda HaLevy, and often mentioned in other variations by contemporary rabbis, such as R Lawrence Keleman. Basically this argument states that Judaism is the only religion that claims to have had a public revelation experience, and since such a claim in ancient times would be hard to promote if it were a hoax, it must be true. There have been many rebuttals to this argument, which I won't go into here. But it does raise an interesting question that is as relevant now as it was then: how does a religion begin? How does it come to be that somebody starts a tradition that others come to accept as being true? We can believe that ancient man was gullible, didn't understand nature, and the like, but that doesn't explain how people have come to accept modern invented religions such as scientology or mormonism. Once a religion has become established, its easier to explain the phenomenon, but how does it all begin?
I think in many cases, some beliefs may have begun from a story that had a kernel of truth to it, and then became embellished. In other cases traditions may be "borrowed" from surrounding cultures. This is obviously true of the Abrahamic faiths. Judaism itself borrowed from other surrounding cultures, as demonstrated by the Ugaritic texts.
Perhaps the same question can be asked of culture itself. How does a culture begin?
I am eager to hear commentors thoughts on this subject.