According to the creation myth in The Way to Rainy Mountain, how did the Kiowa enter the world?

In N. Scott Momaday's The Way to Rainy Mountain, the Kiowa are portrayed as a mysterious "tribe of hunters" who came from the mountains of western Montana and eventually came to control a broad swath of the American Great Plains. Throughout the book Momdaday traces, in his imagination, the history of the Kiowa. He learns much of what he knows from his grandmother. He states that the Kiowa believed themselves to have emerged, one by one, from a hollow log:

According to their origin myth, they entered the world through a hollow log...they emerged from a sunless world.

In fact, the Kiowa name means "coming out." It's left uncertain as to where they ultimately came from and what was at the entrance of the log. The exit place, of course, were the mountains, plains, and valleys of middle America. This myth seems to strengthen the mystery of the tribe.
Other myth stories are included in Momaday's narrative, such as the origin of the stars in the night sky. Kiowa legend says that seven sisters and their brother were playing near the slopes of Devils Tower in the Black Hills of northeastern Wyoming. It seems the boy is suddenly "struck dumb" and turned into a ferocious bear which chases his sisters up a tree. The sisters are "borne into the sky, and they became the Big Dipper."
https://public.wsu.edu/~delahoyd/momaday.html