in most of the songs like this, I always 'suspect' that there was originally one story, but in the days of almost TOTAL oral tradition, the story was mis-rembered, 'improved', shortened...etc..i.e. processed....we can seldom prove it one way or the other, but we still learn a lot about ourselves as we try to find a 'reasonable' explanation for the variants and similarities. (Maybe they changed 'em to get around an early version of Harry Fox? *grin*)