Look at Noel’s clothing. Had you not known anything of his game, you probably would have thought he was from Oerba. Of course, he comes from an undefined farseer tribe. According to the Final Fantasy XIII-2 Datalog:
Oerba is an abandoned village located in the northern reaches of Pulse. The sand that covers the ground is powdered crystal that fell during the War of Transgression.
In recent times, large numbers of Cie’th have been seen in the area. Presumably, they were created from living humans to serve some mysterious fal’Cie purpose. Cie’th are former l’Cie who failed to complete their Focus.
Oerba remains an abandoned village before Noel’s time. Yet, this doesn’t mean that the Oerban people couldn’t have migrated to other areas in Pulse, creating a new tribe. Living on the harsh plains of Pulse would explain the need for hunters.
If Fang and Vanille could survive, why not Noel’s ancestors?
Fang’s original conception was male. For all we know, Fang’s original conception could have inspired Nomura when designing Noel. And Toriyama supposedly had the idea of a trilogy, including a couple of themes and characters. Perhaps Noel would have carried the Oerban line, as Fang and Vanille’s distanct descendant. Yet, only in an alternative Final Fantasy XIII game.
Had this been true, Noel would have still been an anomaly in the timeline. Only here, the reason would have been vastly different. Etro wouldn’t have summoned Noel, and his existence would be in danger. In the same way Lightning disappeared from the timeline, Noel would have entered Vanhalla.
A Time Gate would have opened during 700 AF. Upon Lightning explaining to Noel the situation, his motivation would have been to save Fang and Vanille. Along with Serah, his mission would have stayed the same: resolve the paradox and save Fang and Vanille. Of course, he and his foil Caius would have had the same motivation as in the original game: save Yeul.
Yet in development, things change. Summoning Ragnorak and encapsulated in crystal would have raised the question of how Noel came about. Of course, this would have been the reason for his anomaly status. Yet, once Fang became female, Noel as her and Vanille’s descendants wouldn’t have been an option.