What is the theme in The Source; a Novel by James A. Michener?

The Source is basically a journey through the history of the development of Judaism, from the days of paganism to the 1960s. It begins at Makor when Ur lives in a cave and is a pagan. After Ur, there are a variety of different pagan gods at the site, including Baal. When the god El-Shaddai appears, the emphasis begins to shift to monotheism and the beginnings of Judaism as he evolves into the god Yahweh. As Yahweh develops, paganism becomes the strength of the Greek and Roman empires and the followers of the one god have to find ways to exist within these frameworks as many Jews are killed during these times.