My theory on the clues they’re dropping so far, flame away at it:

Sometime in the 21st century, humanity on Earth destroyed itself. Somehow, technology was developed that would allow these five people to be reborn thousands of years later and thousands of light-years away. Ref: Tyrol and Tigh’s flashbacks—in Tigh’s, the words of Ellen make this point explicit. Tory and Anders' earlier statements make it clear that these five people knew each other; Anders had played “All Along The Watchtower” for them when they were alive back then.

Possibly there was some plan or technology to re-boot humanity, which happened on Kobol with a stop at the algae planet, where the Temple of Jupiter was made. Then from Kobol, the exodus to the Colony planets happened, and humanity once again began to repeat the pattern that took place on 21st-century Earth: the development of AI and artificial life, which led to an apocalypse. Ref 1: the slight variations on Centurion bodies that are found, which aren’t Centurions as they’re “currently” known, but are indeed Centurions. Ref 2: the episodes on the algae planet, and the episode where the ancient Earth satellite is found, which contained a disease that Colony humans developed immunity to long ago.

The obvious inference is that a Cylon-creating society happened on Earth, and this led to the destruction. In fact, it could be that the development of Cylons was explicitly pursued as a means to cheat death, as the Five did; in the previews for “Caprica”, the prequel series in production, this is explicitly stated as being the case—a scientist is pursuing a way to replace his dead daughter.

By the time the Five are reborn, a Cylon apocalypse is happening yet again, just in a slightly different form in this rebooted human society. Because, guess what, this has all happened before, and it will all happen again.

The Final Five are therefore “Cylons” only in the sense that they’re a form of artificial life that’s allowed them to cheat their original deaths; note that all the skeletons on Earth are declared to be humanoid "Cylons".

Viewed this way, the current “humans” are also artificial life forms or, more properly, their descendants. They’re different only in that they’re just not engineered copies of humans that once existed on 21st century Earth.

Is Starbuck a “Cylon”? Probably not. No other “Cylon” of either the pure replicant style or these reborn humans have ever recognized her as such. Also, as other posters noted, the identity of the Fifth Cylon was made explicit in the last minute of the episode anyway.

If the above is true, Starbuck’s been copied, probably using the same tech that set this whole thing in motion. And there’s some third party out there utilizing this tech to manipulate events for this end, another point that was made explicitly clear by Starbuck herself in the midseason finale.

The final 9 episodes, as was set up in this episode, are therefore about answering these questions. Who’s manipulating events, and how, and what exactly did happen thousands of years ago that caused the events of today. And what ultimately happens to the Galacticans and Cylon characters of today, et cetera.

As I see it, this whole plot is heavily at play in the fields of Philip K. Dick, which is a place I’ve been waiting for them to explore ever since the opening minute of the first episode, when the new Cylons were seen to be PKD-style replicants.

In fact, viewed through this lens (assuming any of this is true) the whole thing’s a PKD wet dream—the themes of questioning what it means to be human (or, for that matter, what it means to be a Cylon), what it means to be alive or dead, the idea of what artificial evolution might lead to, the idea of infinite loops, the idea of godlike forces manipulating events behind the scenes.

So, yeah, if this holds, “All Along The Watchtower” REALLY IS the “All Along The Watchtower” that we know.

Where people seem to be stumbling is that the original cheeseball series implied that this was the story of how life began on Earth, capitalizing on the “ancient astronaut” thing that was all the rage at the time in the late 70s. Thus these character names were the origin of our myths, and so forth.

But no such claim was made about the time frame of this series. Makes perfect sense to me that this is actually our far future, not our distant past, and that Moore reimagined it flipped—they’re not our ancestors in this version, we’re theirs.

And hold water this theory may not, I’ll be the first to admit. It has a lot of holes. But it explains to me a lot of the clues that have been dropped along the way.

Moore claims to have known how he wanted to end the series since sometime in the middle of the first season, so this is not the typical “Lost” or “X-Files” situation where they’re desperately trying to tie up crap that they put together randomly to hold viewer attention in the first three seasons.

Whatever. Clearly it’s a shitty show because phones have cords and there’s too much melodrama in one single episode. Whatever was I thinking?

Actually what I’m thinking is that HH did way too much E at Burning Man and fried some of the synapses that would otherwise enable one to speculate on BSG’s plot like this. Try having this kind of discussion about the plot of, say, Star Trek. Why BSG does in fact rock should become more apparent after that.

http://featuresblogs.chicagotribune.com/entertainment_tv/2009/01/final-fifth-cylon-ellen-tigh-battlestar-galactica-dualla-dee-.html

Answers some questions about the show process and how this episode came to be written, and how they arrived at who the 5 were, et cetera. Pretty interesting.