No we don't, the word of jim that talked about this only said he did a rite of ascension to get to where he is. It never said he was a human before. it might turn out that he was human but it isn't proven at this point yet.
Im calling 'shenanigans' on this one; the quote from JB came out from the question of what would have happened to cowl had he succeded in casting the ascension ritual; the implication of ' he would have become a god, just like the erlking did. How do you think the erlking bacame that way in the first place?'
seems fairly clear to me that the erlking was hum,an at one point.
as he appears very not human now, it is allso obvious to me that his appearance or nature changed via the ritual or what happens afterward. Or conversely, he changed his appearance to suit.
futhermore, Mab can change her appearance at will,and has done sop in the books; why cant erl?
as to the next objection, it allso seems clear to me that such rituals require human sacrifice. Of the three we have seen so far, all three would have drawn their power from large scale human death. To assume Mab was a little fairy who went around sacrificing lots and lots and lots of other little fairies seems unlikely when Kemmler started world war 1 to jump start his ritual.
and having Molly dropped at the later part of the ice age actually makes some sense- she did the ritual to become Mab to restore balance to the world, thus saving it.
and not to get into TT subjects like global warming, but look up snowball earth. its rather fascinating. You used to be able to ski from the north pole to the south without much problem.
PS: Ducks dont care about the names of water bodies. We just crap in them.