Last night I read that the first five books of the Old Testament were compiled by the residents of Jerusalem when it was ruled (occupied?) by the Persians who allowed the residents more autonomy in exchange for having their own codified set of laws. There were indeed multiple sources representing and merging the abrahamic lineage tradition with that of the desert wanderers (presumably Moses' 12 tribes.)

Is that exactly what happened? Who knows? Like Ken Ham and pete, I wasn't there. But it seems plausible and it seems to shed a little light on the "one indisputable source" theory.