The last big question really. The most interesting idea I have heard is that some sort of being created the island, around the time of the Egyptians perhaps due to the hieroglyphs. That they put all the evil in the world and buried it in the island, then used some of the worlds goodness to seal in the evil.
Others have apparetnly looked at the markings on the stone "cork" and found out this "The runes on the cork were in enochian script. a sort of language of angels,A proto-proto hebrew: the highest order of angels who have animal heads -Egyptian gods-"
So what does anybody else think? Or does it even matter, is what the island stands for more important than where it came from?