How/why did monotheism evolve?

From what I know, many early religions involved multiple deities. But then it seems that in what we now call the West and the Middle East, a very definite change toward monotheism occurred. What brought that on? Was there some functional reason? Did someone decide it worked better? What was the impetus to discredit polytheism?



I know a little bit about how it came to dominate Roman thought, but the changes I'm thinking of occurred earlier than that.

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