So after watching this series from day one and having worked on several episodes as a background and principal actor I have formed a theory. I believe the island is the original island of Atlantis. Although history and legend states the island disappeared into the Atlantic Ocean, in reality, it was "moved" by the residents of the island in response to some kind of catastrophe. Possibly the failed attempt at invading Athens. After the failure, the leaders of Atlantis feared massive retribution and therefore used the underground wheel to move the island to safety.
The stone statue that is seen in whole in the past but with only the one four-toed foot later on most likely was a statue in honor of Poseidon, the God who was given possession of Atlantis and who gave his son Atlas rule over the island. Furthermore, I believe the "smoke monster" is one of Poseidon's children left on the island to "judge" the inhabitants as it sees fit, allowing those who are worthy to live and those it deems "bad" or unworthy sentenced to death (as in Eko, the pilot of flight 815, etc.)
The hieroglyphs seen in several places on the island including in the temple and in Ben's doorway to the holding place of the "Smoke Monster" most likely refer to the Egyptian hieroglyphs found by the Greek philosopher Crantor in Egypt which refer to Atlantis and the Egyptian priests who claimed to have visited it. From wikipedia: In Plato's myth Poseidon fell in love with Cleito, the daughter of Evenor and Leucippe, who bore him five pairs of male twins. The eldest of these, Atlas, was made rightful king of the entire island and the ocean (called the Atlantic Ocean in his honor), and was given the mountain of his birth and the surrounding area as his fiefdom. Atlas's twin Gadeirus, or Eumelus in Greek, was given the extremity of the island towards the Pillars of Heracles. The other four pairs of twins — Ampheres and Evaemon, Mneseus and Autochthon, Elasippus and Mestor, and Azaes and Diaprepes — were also given "rule over many men, and a large territory."
Poseidon carved the mountain where his love dwelt into a palace and enclosed it with three circular moats of increasing width, varying from one to three stadia and separated by rings of land proportional in size. The Atlanteans then built bridges northward from the mountain, making a route to the rest of the island. They dug a great canal to the sea, and alongside the bridges carved tunnels into the rings of rock so that ships could pass into the city around the mountain; they carved docks from the rock walls of the moats. Every passage to the city was guarded by gates and towers, and a wall surrounded each of the city's rings. The walls were constructed of red, white and black rock quarried from the moats, and were covered with brass, tin and the precious metal orichalcum, respectively.
According to Critias, 9,000 years before his lifetime a war took place between those outside the Pillars of Hercules at the Strait of Gibraltar and those who dwelt within them. The Atlanteans had conquered the parts of Libya within the Pillars of Heracles as far as Egypt and the European continent as far as Tyrrhenia, and subjected its people to slavery. The Athenians led an alliance of resistors against the Atlantean empire, and as the alliance disintegrated, prevailed alone against the empire, liberating the occupied lands.
I think that Jacob, Richard Alpert and the smoke monster are three of these sons of Poseidon who still occupy the island to this day.
As for the events we are currently seeing happen on Lost, I believe it is a sort of self-fulfilling prophecy version of time travel. Consider that if Locke hadn't gone to Richard Alpert in the 50's, he wouldn't have later been visited by Richard and eventually chosen as the new leader of the Others. Also, if Sawyer and Kate had not taken Ben to the Others after Sayid had shot him, he wouldn't have become the bastard he is today. I believe that we will learn that the corpses "Adam and Eve" that are found in the cave by the flight 815 survivors are really either Sawyer and Kate, Jack and Kater or Jin and Sun. Considering the twists of irony that we see so often on Lost, I would venture to guess it's Jack and Kate from 1973 that are in the cave since it's Jack and Kate from 2004 who find the corpses. Judging from the white and black stones found on them, I would guess that one of them was voted out of the Dharma initiative sometime before the purge and the other joined them out of love and loyalty.
According to the Novikov self-consistency principle of time travel asserts that if an event exists that would give rise to a paradox, or to any "change" to the past whatsoever, then the probability of that event is zero. In other words, even if you traveled back in time and killed your own grandfather, you would still be born through some other means since you were still able to exist and go back in time to kill your own grandfather.