I think you could test religion experimentally.
If you were to drop a load of kids on an island secluded from outside influence and left them to their own devices, 1 of 3 things should happen.
1. They spontaneously develop a major religion proving that there is a god
2. They don't develop any religion proving that there isn't a god
3. They develop their own religion proving that the development of religion is a basic factor in the human condition.
I think 3 is the most likely to happen, it's in human nature to attribute the unknown to some malevolent entity as a way to get some sort of mental handle on it. When cavemen worshiped the sun and the moon and the stars and things that went bump in the night it gave them a framework to turn the unknown into the known, as nature abhors a vacuum the brain can't handle the unknown and will do what it can to rationalise it's experiences, it's basically a delusion generator.
On a different note I thought this was quite funny