It's interesting that Momaday prefaces his account of the Kiowa creation myth with the words "You know." The full sentence is "You know, everything had to begin, and this is how it was: the Kiowas came one by one into the world through a hollow log." This tells us that the story is a familiar one, one that has been handed down orally from generation to generation.
As regards the substance of the Kiowa creation myth, it's notable that only a relative few were able to emerge from the hollow log. This is supposed to explain why the Kiowa is such a small tribe. According to the story, a pregnant woman got stuck in the log, preventing anyone else from escaping. So those who did manage to escape were very fortunate indeed. None of this is to suggest that the original members of the tribe were some kind of morally superior elite; they just got lucky.