If you believe the theory that the early Hebrews were not an existing ethnicity but only a band of diverse, marginalized peoples, then Yahweh's jealousy makes more sense. Durkheim told us that God was a reflection of society; the way we imagine God is really the way we think about ourselves. God may have created us in his (her?) image, but we have certainly returned the favor by recasting God in our image. If your society was otherwise well integrated, your God (or, more accurately, gods [plural] since none of them were all that restrictive) didn't need to be preoccupied with monopolizing your allegiance. If your society is, however, less than naturally cohesive, then your God (and it has to be just one God to focus that loyalty) demands your unquestioning and singular devotion. I am claiming that monotheism was created as a functional prerequisite for a particularly problematic ethnogenesis.