I'd go further even... To say that religion developed under a cultural shock brought by, perhaps accidental, extraterrestrial contact with us as a less civilised species... Some 2000-5000 years ago. (can't be bothered to figure out the exact time when someone wrote the bible/q'ran/shem up...)

Seeing there was no possibility to live with humans on an equal basis, or perhaps deeming them not yet ready for further contact, the aliens left thereafter... Probably annihilating every trace of their existance. To a prehistoric commoner, that would have looked like a higher power...

Angels, demons... Ach, the images were all drawn up later. An angel was a good alien, one who liked to assist the "native" earth population, a demon was one who would try and scare them off... (probably just a security guard or such).

A theory, nothing more... But a possible one imo. And one that would render a few religions obsolete... when they find out... God was but the name of the captain of the crashed ship...