nadenitza: Well i think it's safe to say it's possible, the religion itself doesn't matter really, given there are medieval tribes in history that had many gods, someone sometime must have came to some supernatural conclusion without being imposed by others - and starting spreading it... hmm
This is pretty interesting because it actually means we are (or at least some of us) genetically dispositioned to believe in the supernatural, if we can come to a supernatural conclusion by our selfs. Does that mean our genes are prone to theism, or more specifically, does that mean that if we are destined to believe in something supernatural in the future, are we are actually theists to begin with? If the medieval guy came to the supernatural conclusion, was it just a blind luck or does it mean something more... gatdaymn... my mind starts to hurt...
The explanation is quite simple, actually. We are curious, seek answers, and have a lot of imagination. The processes which cause most of stuff like rains, lightening etc. are not instantly apparent and are not easily comprehended without a lot of abstraction and understanding of a huge amount of related problems, so instead, people start thinking in terms of what they know. What they do know is their own way of life, and their surroundings - so people start relating to that. They know that by following a certain procedure, they can create fire or forge a sword in more advanced societies, so obviously, there has to be something, much more powerful than them, what is causing all of these things to happen. And there you have it, gods are quite simply the easiest way to explain a problem - and all people are alike in how they think, so they will all eventually come to the same conclusion. Not because they would be 'genetically engineered to believe in gods', but because gods are the most straightforward, most comprehensible and laziest way to explain how the world around them works.