The Dragonborn, emerging from the swamplands of the Baja peninsula, hardly look human at all. They claim their clans were blessed by a rainbow-colored serpent flying across the sky, but that's silly... right?
Still, though. There's something more to these creatures. They survived the Crap Times in the full exposure of everything terrible, and emerged with their minds seemingly intact. But whether that was the result of the blessing of an ancient Aztec god, one of the mythical dragons, or just mutated by the fallout is a matter for faith.
As for the dragons themselves, some believe they are merely lizards turned massive through the effects of the arcane fallout, but legend attributes much more to them. It's no surprise that the simple, wild folk from the swamps would claim something so grand. No post-human has been able to prove the existence of a gigantic, intelligent, flying, element-breathing reptile, though the bounds of what is possible have certainly been pushed to their utter limits since the Big Wake Up. You'd be hard-pressed to find any post-human who would claim that dragons can't exist, but it is a lot easier to say that the strange Dragonborn made up their heritage.
Nonetheless, the Dragonborn are proud and self-sufficient people. They believe they were created for a purpose, and though what exactly that purpose is varies from clan to clan, their actions out in the world prove it. They fear little and are as unwilling to back down from an opinion as they are from a fight. They tend to hate asking for help, especially from anyone who isn't also Dragonborn, but they can still function well with others. Dragonborn live to help others, even the races they view as somewhat inferior.