Boltar and the hot blonde (#6) could only have a baby together (she made this very clear to him that it is their baby) if she is real (cylon) and he is real (human).
This means that a sample of his sperm or same sample they could of cloned him from is on a mothership somewhere with a #6 female serving as an incubator - perhaps the very same number 6 which transmits images into his head. Remember something sets off the sleeper Cyclons and gives them instructions from afar.
Stargate, Atlantis, BSG and soon Firefly............somebody likes us Sci-Fi geeks.
