Do you realize what you're presuming? Do you realize what the title of the game is?? Myth. This is—if you truly MUST put rhyme or reason to it, saying that this world might exist in an alternate reality—a timeline which developed, likely, LONG BEFORE the creation of Earth or even the Solar System. This being the case, a completely different world, which happened to be just like Myth, evolved.
My advice: Keep to trying to work out oddities in the game itself. There are more than enough things to debate within the giving framework of the game without trying to expand beyond that framework first. If you're looking for answers and ideas, I personally suggest you read the Poettic Edda. Once again, this world is MYTHICAL :-). It can work however it wants to work, as long as the basic stuff, which is normally covered, makes sense :-).
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