I'm not sure if this is the right place to ask this since this mostly deals with pre-historic civilisations, but I figured some of you guys might know something about it.

I'm talking about things like the celtic cultural groups you hear dominating central Europe before the start of classical Antiquity, or for example this picture regarding pre-European artic tribes in North America. It interests me greatly because in the corresponding, it mentions that the "Thule were a strong people with a history of warfare, and they had better weapons than the Dorset. The process of "driving off" the Dorset, which is recounted in their legends, would likely have involved direct conflict". Which then, to my analytic mind, creates some questions.

How could a very wide, loose organisation of tribes create a distinctive divide between themselves and another, very loose organisation of tribes? How would an isolated Thule village in say 1250 AD, know that their neighbours 10 miles across the lake were filthy weak Dorset, whereas their Thule brethren 500 miles down the coast were somehow "more similar" to themselves? Would a pre-agricultural society have very limited knowledge of the world beyond their immediate surroundings, and hence would only know how to compare themselves with those whose existence they were immediately aware of? How can something as conceptual as a "tribal group" come about, given the diverse, scattered and isolated nature of pre-agricultural civilisations?

As usual, thanks for all the responses? Knowledge is power!