The alternate timeline scenes are JACOB'S flashbacks by CruzaderJC

Keep an open mind, I'm purely speculating a FANTASTIC way for the series to play out.

The Alternate Timeline scenes we are watching this season are JACOB'S flashbacks... a biography if you will. Imagine we watch all the original characters bump heads and meet each other in this alternate reality. But in this reality, somehow Jack and Kate end up together, get married, and have a child... Jacob.

Now before you roll your eyes, hear me out. Imagine there is a coming apocalypse, and Jacob and Aaron (Claire's baby) are friends who are working for the Dharma Initiative, trying to prevent the world from ending. In doing so, they unlock the secret to time traveling, and in desperation, travel back in time to save their parents, and their parents' friends (Sawyer, Locke, etc.)

The time traveling "device" is actually the Island as a whole, and Jacob and Aaron have several mishaps, landing in incorrect time periods (Egyptian, 1800's, 1970's, etc.) thus many civilization come across this time traveling machine.

They finally arrive in their parents' time period and summon them to the Island in a desperate attempt to alter the future. They will not allow any children to be born, so those children will not experience the horror they did in their apocalypse.

Imagine the Alternate Reality scenes leading up to the apocalypse, with Jacob being sent back in time to prevent it, leaving behind his parents, Jack and Kate. In the Standard reality (the one we've been watching all along), Jacob reveals he is Jack and Kate's son from an Alternate Future.

{Damon and Lindelof have stated there is a significance to the title being LA X, instead of LAX. In several science fiction series, most notably X-Men, there tends to be an alternate reality miniseries, usually called Future X, or something like that. In all of these alternate reality series, the X future shows a pre- or post-Apocalyptic setting, possibly where the Alternate Timeline scenes could be leading to}

The final twist could be that one, or some, of the main characters is RESPONSIBLE for the Apocalypse, thus Jacob interested in this specific group of people. In the alternate reality, it is not clear who exactly is responsible, or which of this group can possibly prevent it.

I think a final climax could be them realizing Jack is the reason for the Apocalypse, and so Jack and Kate decide to sacrifice themselves at the end of the series, in order to save the world... Jacob's mission successful, all the while allowing his parents and their friends recognizing their own flaws during this adventure, and overcoming their own personal quests.

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