The interpretation is that the Yana community — or at least the population from which the Yana individuals were drawn — was large enough to maintain genetic diversity through outmarrying with other groups.

They were not a single isolated band of perhaps thirty individuals who never interacted with outsiders.

They were connected to a broader network of people, a meta-population distributed across some larger geographic area, within which individuals moved and married and contributed genes to communities beyond their immediate birth group.

This makes intuitive sense for a hunting community in the Pleistocene Arctic.

A single band of thirty people could not hunt mammoths effectively — the animal is too large, the risk too high, the infrastructure of processing and storage too demanding.