Ethnic group defined
The term ethnic group is generally understood in anthropological literature (cf. e.g. Narroll 1964) to designate a population which:
1. is largely biologically self-perpetuating 
2. shares fundamental cultural values, realized in overt unity in cultural forms
3. makes up a field of communication and interaction
4. has a membership which identifies itself, and is identified by others, as constituting a category distinguishable from other categories of the same order.
This ideal type definition is not so far removed in content from the traditional proposition that a race = a culture = a language and that a society = a unit which rejects or discriminates against others. Yet, in its modified form it is close enough to many empirical ethnographic situations, at least as they appear and have been reported, so that this meaning continues to serve the purposes of most anthropologists. My quarrel is not so much with the substance of these characteristics, though as I shall show we can profit from a certain change of emphasis; my main objection is that such a formulation prevents us from understanding the phenomenon of ethnic groups and their place in human society and culture. This is because it begs all the critical questions: while purporting to give an ideal type model of a recurring empirical form, it implies a preconceived view of what are the significant factors in the genesis, structure, and function of such groups.
Most critically, it allows us to assume that boundary maintenance is unproblematical and follows from the isolation which the itemized characteristics imply: racial difference, cultural difference, social separation and language barriers, spontaneous and organized enmity. This also limits the range of factors that we use to explain cultural diversity: we are led to imagine each group developing its cultural and social form in relative isolation, mainly in response to local ecologic factors, through a history of adaptation by invention and selective borrowing. This history has produced a world of separate peoples, each with their culture and each organized in a society which can legitimately be isolated for description as an island to itself.
- 1969. Ethnic groups and boundaries. The social organization of culture difference. Oslo: Universitetsforlaget.