Very little accounts of written history in the Bible, Quran or Torah can be corroborated with the written history of pagan civilizations during the same time periods. What does this tell you?
Also, nearly all monotheistic religions began by 1 man claiming to talk to an angel (who is talking to god), by talking to god himself, or by being god (or his son).
It was only later in these religions history that duality was accepted. (good vs bad). This most likely happened during the rise of Zoroastrianism.