Asams10, I'm not sure if you are trying to debate me or U&M.; All I am trying to do is represent what U&M; write in their book. I never wrote that I personally agreed with their hypothesis; it is their hypothesis, not mine. If you think I have incorrectly summarized I&M;'s position, let me know.  But I won't defend whether that position is correct or not; it is their point-of-view, not mine. -