Or maybe it is just familiarity. You could have a village where everyone knows everyone else and most people have never travelled more than ten miles from wher

Or maybe it is just familiarity. You could have a village where everyone knows everyone else and most people have never travelled more than ten miles from where they were born. Or a city of thousands. Of course one will be more trusting than the other because people trust the people they are familiar with. And understandably more isolated communities will have more unique culture. Culture and ultimately race are more a consequence than a cause.