Maybe there's a recessive gene that causes some tone difference. Maybe there's some historical war that caused the blahblahblah migration of the whoseits to the whatsits. Or maybe it's not part of the story at all and doesn't need to be.
When I meet a new black person they don't spend a bunch of time explaining to me why they're black. That would be pretty weird. It sounds like you have some real hangups about race that just isn't shared by the writers.
When I meet a new black person they don't spend a bunch of time explaining to me why they're black. That would be pretty weird. It sounds like you have some real hangups about race that just isn't shared by the writers.