In a flash of inspiration; it suddently occurred to me what happens.
Sawyer, Locke, Juliet and the others are time travelling, when they are chased by the 'other others'. In the timeline we have seen, they escape, and manage to shoot someone in the outrigger chasing them.
BUT... what would happen if Jack had been there when the time travelling started? Could he have stopped Sawyer, and Locke from turning the wheel? he will now have a second opportunity, and this time Jack stops the group. He prevents Locke from turning the wheel, he prevents the whole Dharma times from occurring, and he changes the past. He even stops Jacob from interfering. Everything so far we have seen actually happened. As soon as Jack stops Locke from turning the wheel, it changes everything, we are thrust into the new scenario, into the FS, because if the wheel never got turned by Locke, none of the events in the Dharma times, including Ben in the pool, becoming leader, Jughead, incidents, purging Dharma, Swan, button pressing, none of it happens.
Brilliant. Why have we never thought of this before!!!