But, I digress. I intend to write on a hypothesis of mine concerning the evolution of the concept of the supernatural, and I want to commit myself before reading the books on religion. Obviously, this hypothesis will probably be subject to subsequent modification.
Humans appear to be distinguishable from other animals not by curiosity, but by a propensity for concocting explanations for that which we investigate. Obviously, I am assuming that your average kitty does not concoct metaphysical explanations for objects examined during fits of curiosity.
By UPA, I refer to Unidentified Physical Agencies, which I use to indicate those physical mechanisms that are not immediately obvious to the human observer. Grant LaFleche posted an interesting mention of Al Hazen's 10th century overturning of the notion that our eyes see by emitting rather than receiving light. It is extraordinary that none of those who viewed the eyes as actors rather than perceivers had never wondered why they could not see in the dark at the same time that others could not see in the dark! Surely, such miraculous eyes could have acted as the earliest flashlights – much more convenient than barking one's shins after nightfall.
The simplistic, animistic UPA meme was amplified into the notion of Unifying Physical Agencies (deities) and ultimately into the notion of the Ultimate Physical Agency (Yahweh et al.) Now the UPA has come to be called the 'supernatural', a term that embodies both the purported supremacy of this 'ultimate physical agent' and the fact that this agent has proven physically undetectable.
One wonders why a loving God – who wished to be feared, obeyed, and worshipped and who had accordingly dictated an admittedly inconsistent tome – would not have understood the frailties of his special creation and made matters clearer. He could have saved the discoverers a great deal of trouble.