I guess it's a question of scale. When you have group A differentiating itself from neighbouring group B (in ways which feel significant but which don't quite add up to a communications barrier), and group B is differentiating itself from group C, and group C is differentiating itself frrom group D, what you end up with when you zoom out is a continuum from A to D.
I guess it's a question of scale. When you have group A differentiating itself from neighbouring group B (in ways which feel significant but which don't quite add up to a communications barrier), and group B is differentiating itself from group C, and group C is differentiating itself frrom group D, what you end up with when you zoom out is a continuum from A to D.