The Final Five & the modern humanoid Cylons are not the same. The Five were the last five remaining humanoid Cylons from "Earth", capable of procreation, and descended from the original 13th Tribe of humanoid Cylons.
Resurrection Technology was an *old* technology, used way back on Kobol, but long since lost. The Five re-invented/re-discovered it to save themselves, after learning of the upcoming nuclear apocalypse on "Earth".
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Mo's Blog at the Chicago Tribune has now been updated with a Q & A session with the writers of "No Exit", last Friday's exposition-heavy episode:
http://featuresblogs.chicagotribune....omer.html#more