Also, in that Episode, it seems that it's the first time we've seen colonials with what they think is direct information on Earth itself.
Not quite, the first time they saw what they think is direct information on Earth itself was the constellations at the Temple of Athena I believe on Kobol itself. Thats why Adama tells Gaeta to take his time verifying that they are in their correct spots.
Surely this means that there was contact between Earth and Kobol before the 12 tribes left. And it seems to me, that Earth might already have been established before the 13th left Kobol too. So to me it discounts the idea of Earth not being the point of origin within this BSG's mythos.
Can't leave breadcrumbs to somewhere you've never been so yeah either someone left Kobol settled Earth then returned to the 12 colonies with the "prophecies" of Pithia leaving clues to it's location on the return trip or Earth was the starting point and Kobol was second.
What I meant about the colonials understanding of Earth, is that it was the first time we've seen info they've had from before the escape from Caprica et al.
The Hybrid also said that they should not follow Kara.... as far as I can see, that's exactly what they have all done.
The viper was pointing the way to Earth, but then, so was the arrow of Apollo, and the Temple of Jupiter and the Ionion Nebula etc.... this world could be another guide to that place, another stepping stone.
I don't think it would take much to make it so. You just need them to find a temple or sealed documents saying the world is called Terra, and that some kind of cataclysm is occurring, and we've decided to return to humanities birth place... .Earth. This would cause major upset for the colonials because they think they originated on Kobol.... and I think it would then be a good lead to the idea that the Colonials were the Kobol version of Cylons, and they caused the destruction, and that the 12 tribes were based on 12 models of Cylons that existed. Where as the 13th tribe were the surviving Humans who fled back to Earth. So all of this has happend before and it will again......