It states that Yahweh was a sort of war god in Canaanite polytheism alongside other gods, such as Asherah & Baal. A cult arose that worshiped him above all others, but they only gained power during conflict. They were a form of monolatrism, meaning that they acknowledged other gods, but only allowed for worship of one (Yahweh). Over the centuries, this became monotheism and the modern big three religions... at least, that's what I got from it. I only watched it yesterday, so my understanding is rough.
These videos describe it better than I: (I realize they could be biased due to the atheism of the videos creator, but it made me curious. He lists his sources and a few corrections in the video description.)
Edit: I should mention these videos are a part of a series on a mans deconversion from Christianity to atheism, so some of the things mentioned will be unrelated to the above theory.
Edited by Penumbra, 04 January 2012 - 05:21 PM.