Jester Canuck said:
Everyplace has "city folk" and "country folk"
Ah, so you replace racism with classism. "You see, the reason we live in cities and you live in the backwoods is because
we're better suited to it than you. See, you're SUPPOSED to be poor dirt farmers. And we're SUPPOSED to be urban elites. It's in our natures!"
No no no no no no.
Any way you slice it, dividing the human race into "subraces" is potentially
vastly problematic. Because unlike any of our fantastic species of never-existing human-esque critters, humans actually exist, and any division you put on them in the game is going to be interpreted (even unfairly) as something the designers believe about humanity to some degree.
Being human is not about
what you are, it's about
who you are. In a fantasy setting where the lines between "archetype" and "stereotype" are not nearly as boldly drawn as they are in the real world, that's even more true. You cannot say anything about a group of humans that is going to be a fair generalization. The stuffiest of stuffed-shirt noble jagoffs can come from a cowplop farm, and the ragingest barbarian who ever swung an axe could've been born with a silver spoon in her mouth. You can say "dwarves are stout," and sure, what with their Con bonus, you can see that. You shouldn't be able to say the same thing about humans. Even a category of humans. The fantasy archetype of humanity is variety, possibility, potentiality, and flexibility.
While I'm all for cultural signifiers, even mechanically (in Backgrounds, for intsance), dividing people into mechanically distinct "from birth" groups is not something that D&D can in general get away with.
As always, you should do what you'd like in your own games, and if that means adding human subraces, well, whatever. I think it should be fairly easy for you to do so. I DON'T think these should be official. There's nothing but problems in dividing up people like that.