"the original accounts" ..... these would not in fact be the original stories as those stories would have not been recorded in permanent form, instead they would have been part of an oral tradition.
Here in Australia we have ample evidence of this loss of lore, culture and religion being a result of lack of permanent records. It was assumed that the indigenous people had no 'real' (as in European) culture as there were no writings and the sacred drawings were deemed to be primitive and worthless.
I'm not sure we are much more enlightened now, but much has been lost of indigenous belief, not least because christians insisted it be destroyed or ignored.
I suggest the original stories on which Genesis was based would reach back further than permanent recording can go and they have survived because at some remote time (well before the writing of the bible) some scribe preserved the traditional tales by writing them down.
