How the hell would I know what economists think and do? Or what they wear or what they eat? I threw those terms around from Brenner's article only to indicate that I was too busy struggling with one set of he man concepts to get too deep into the other set of he man concepts from Saussure and Levi Strauss whom MS and Ob discuss in their important debate, and there is no entry into that debate without a very good sense of such theory. Halpike wrote a book on the principle of social evolution which Peter Worsley subjects to some criticism in his book Knowledges, and there is some discussion of it in Tim Ingold's Evolution and Social Life. You have stimulated my interest in the debate between Sahlins and Ob. It will be interesting to see how Sahlins' earlier critique of sociobiology connects with (if I understood you) his critique of Ob's apparent positing of a form of universal rationality hardwired into the human species generally. May I add that I don't know either of the interlocutors.
By the way, I have quoted from Mattick Jr's book Social Knowledge on the need for an anthropological investigation of the discourse of economics as conceptually incoherent, internally contradictory, and empirically disconfirmed but still so vital in the reproduction of a certain form of social life that its absurdity is systematically not questioned.
yours, rakesh