Sahlins, Evolution and Culture, 1960

"[T]o Earth's recent demonstration of the development and perpetuation of cultural differences by ethnic segmentation and economic interdependence among the Pathans, Kohistani, and Gujars of North Pakistan (1956). Significantly, Earth finds a "natural area" approach inadequate, and uses instead the idea of ecologic niche as "the place of a group in the total environment, its relation to resources and competitors," Sahlins, Evolution and Culture, 1960:49