What myth explains why the Kiowas are such a small tribe?

The Kiowa story of creation explains why the Kiowas are such a small tribe. According to this story, every Kiowa came into the world through a hollow log.
The Kiowas essentially originated from a "sunless" world into a world brightened by the light of the sun. Because of this, the Kiowas forever worshiped the sun deity through their yearly Sun Dance rituals. It was said that, despite the Kiowa desire to emerge into the world, not all of the tribe were so fortunate to make their way through. Many had become stuck in a dark world because a pregnant woman had gotten lodged in the log. 
After her, no one else could get through, and this is said to be the reason Kiowas are such a small tribe of people. Upon coming out into the world, the Kiowas had originally called themselves Kwuda, which means "coming out." Later, they called themselves Tepda and Gaigwu. Kiowa is thought to have been derived from the Comanche form of Gaigwu.