All mainstream religions believe in a higher power. What if this "higher power" isn't an ultimate controller of the universe, what if our ancestors misinterpreted what they heard and saw simply because it was so "out of this world". It is quite possible and more logical that what society sees as God is actually a more intellectual being then themselves.
You know how if you start a story and pass it on, it will come back to you differently? Well the ancient Sumerians, the creators of the first written language, believed that a group of extraterrestrials visited Earth and influenced humanity. The story in Christianity is God, his son, and angels taught humanity how to act in order to go to Heaven. Two sentences written about the same thing, with a different choice of words...