What we now call the Christian religion existed amongst the ancients, and was from the beginning of the human race, until Christ Himself came in the flesh; from which time the already existing true religion began to be styled Christian.
— Saint Augustine, Retractationes, I, xiii, 3
Most modern historians of religion disagree with Augustine. The very title of Religion in Human Evolution, the recent magisterial magnum opus of that archon of latter day sociology of religion, the late Robert N. Bellah, aptly indicates their perfectly contrary hypothesis: that monotheism is a late development in a long process of evolution from early and metaphysically confused animism, nature worship, magic, ancestor worship, or the like. Their presumption seems to be that early man was rather dim, compared to themselves, and that any abstract notion he had not derived rather immediately from the rudimentary components of his everyday life was quite beyond him.
But this is of course only a prejudice. As Paul Radin pointed out in Primitive Man as Philosopher, we have on the contrary good reason to think that our earliest ancestors were just as intelligent and percipient as we are.