I'd like to add my name to E's roll of non-theists. Atheist, agnostic...I go back and forth. While I do not have evidence proving specific supernatural beings described in the ancient myths of our earliest civilizations do not exist, currently existing religions have no problem claiming the vast majority of those old religions are fictional. Of course, most of them claim this based on their own ascendance and special relationship with their deity of choice.
When I think about all of the crap I've been personally dragged through in my life thanks to religion, and the crap others that I love and care for have suffered through because of religion, I have a strong personal bias against it. And while there may be no empirical way to disprove through science of the natural world things that supposedly exist in the supernatural...science can disprove claims by religions that are founded in the natural world. There are more than enough claims in the Bible that are patently false...just take the sun standing still in the sky during Joshua's seige of Jericho. If we can prove numerous claims in religious texts false, why should we assume that any of the others are true?
Furthermore, there is a blatant assumption going on just with the term supernatural. There is no evidence that anything supernatural exists. Again, refer to all of the many colorful examples based on said Flying Spaghetti Monster and his Noodly Appendages. An appeal to authority for the existence of anything deemed supernatural is no more believable than a two year old child explaining to their parents about their imaginary friend. If something supernatural really existed, how could it interact with a universe in which nothing inherent to this universe could measure it through our senses or tools? How did these ancient peoples manage to interact with the supernatural if they are a part of our universe that cannot interact with the supernatural?
We may not have direct proof, but we do have logic, which serves in the absence of our five senses delivering us data. If it does not pass logical proofs, then I say it has been proved just as nonexistent as if we had physical evidence to prove it. I mean, if something does not exist, there isn't going to be proof that it doesn't exist, because something that doesn't exist has no proof of anything because it doesn't exist. In the absence of physical proof, logic shows us that the supernatural cannot exist.