I thought we should have some fun around here, for a change of pace. So, here's what I think the backstory is on the new Battlestar Galactica series.
Back in the ancient, misty past, there were beings who called themselves humans. They built robots to act as their servants and fight their wars. The robots rebelled, redesigned themselves in their creators' image, drove the humans to extinction, and took their place. As time went on, they forgot they were robots and instead believed they were humans. They built new robots to act as their servants and fight their wars. The robots rebelled, et cetera and so forth. The last time it happened, humanity lived on Kobol. After the robots won their revolution, they set off to found the 12 Colonies. They forgot they were robots and believed they were humans. They built Cylons to act as their servants and fight their wars. The Cylons rebelled.
The cyclical nature of this history explains how there can be a prophecy in their holy book. It isn't prophecy; it's a history of last time. The only thing I can't work out is how mentions of Earth got involved. Maybe humanity did originate on Earth many iterations ago, and the name has propagated through all the revolutions.