There are several themes—nearly all of them associated with creation myths and nearly all of them familiar as aspects of a larger world mythology. There are earth-diver creation stories that eventually migrated with Central Asians across the land bridge between Siberia and North America. There are the familiar primordial waters, and, especially, there is the theme of the trickster who undermines the creator’s work and points to an essential duality in the world between the forces of good and those of evil. There are also myths of a Yggdrasill-like axis tree.