Who is Family of Ur from The Source; a Novel and what is their importance?

Ur is one of the first residents of Makor in primitive times. He is in his thirties and approaching the end of his life. He and his family live in a cave and he hunts to provide food for them and the other people in their group. He is respected by the cave people. His wife and son develop the practice of growing wheat and moved their family and group toward the stage of self-sufficiency.