"At one time social anthropologists used to complain that their archeologist colleagues had no sense of the overall coherence of human societies. Now [prehistorians] have become committed to a functionalism of a wholly naive sort. They seem to assume that cultural systems and language systems are bonded together and intrinsically stable over long periods of time. If societies are left alone, they stay put; otherwise, they roll across the landscape like impermeable billiard balls. If the archeological record shows that in fact changes have occurred, their occurrence is always explained as the conse­quence of a movement of population that carries with it the products (both material and immaterial) of a preexisting, alien, self-contained culture. As a rule, the alleged movement of people takes the form of a military conquest."