Panspermia - (wiki) is the hypothesis that "seeds" of life exist already all over the Universe, that life on Earth may have originated through these "seeds", and that they may deliver or have delivered life to other habitable bodies.
Now I have no illusions that this theory would ever see the light of day on Lost, nor do I think any theory really explaining the origin of the island or it's properties will be presented on the show. I think the writer's meant it when they had "other Mother" say, "every question will simply lead to another question."
But here's my little attempt to put my need for answers to this puzzle to rest.
I like to imagine that, as stated in the above definition of panspermia, the island is the landing place of a very special meteorite. The meteorite that brought life to the planet.
My evidence: well there's not much.
First, I know that the "life force" in the cave didn't exactly resemble the "seed" of life promoted in the definition of panspermia. But there is a similarity there.
Second, the electromagnetic properties could have possibly been imbued in the island from a very large iron magnetized meteorite.
Third, the ancient Egyptian culture used meteorite materials as part of important or holy items. For instance, 18 items of meteoritic iron have been found in the tomb of Tutankhamen. http://www.gizapyramid.com/meteorite.htm
But lastly, and the most convincing piece of evidence(haha)... The lyrics to "Catch a Falling Star."
"Catch a falling star(meteorite) and put it in your pocket(of magnetism)
Never let it fade away(never let people put out the light)
Catch a falling star and put it in your pocket
Save it for a rainy day (like the day Ben almost dies)
For love(Desmond's key) may come and tap you on the shoulder(like Jacob) some starless night"
I know, I know. It's my first one, cut me some slack. But hey, if a falling star can destroy Hurley's newly purchased Mr. Cluck's fastfood restaurant, you never know.