Cultural materialism?

In the previous post I mentioned the possibility that a very significant change in cultural evolution may have been brought about by a purely cultural development -- i.e., not by a new technology, or the development of a new technique or mode of production, but rather through the emergence of a new cultural form, or through, in a sense, a purely cultural mutation. The change in this case referred to the rise of urban civilizations, usually associated with the advent of farming. But what if farming, at least at low levels of intensity, had been around for some time, many thousands of years perhaps, without giving rise to cities? What if that development, instead, hinged on the idea that the charisma of a god-like ruler was attached to the office rather than to the office-holder, and was supported or maintained by an increasingly powerful class of priests/scribes/administrators, with their associated ritual and mystique? What if it was only through such a purely cultural development, in other words, that significant numbers in the more densely populated regions could be organized and mobilized to supply the labor that not only built the cities, carried on the increasingly complex commerce, and developed more systematic farming practices, but also conquered the surrounding people who lacked such an awe-inspiring "meme" (though, of course, once conquered, didn't lack for long)?

Well, that particular idea, however interesting, might well be wrong. The point I want to make, however, is that such an explanation, were you to make it, would appear to expel you from the camp of the cultural materialists and force you in with cultural idealists. And then I want to make the point that that appearance might be wrong -- first, because the explanation doesn't involve the idealist implication that human agency or will is what directs cultural evolution; and second, because culture itself -- even considered as an imprint on the mental apparatus or neural structure of language-using primates -- is a material thing, with at least as much material affect on the world as a practical technique like irrigated farming. What's important here isn't so much the labels or the disciplinary camps, but the understanding that culture isn't a mere abstraction (nor a matter of conscious choice) but has a real, concrete, and material presence in the world.