Let's assume that cultures, in all their fractal variety, do in fact "evolve" -- that is, they change over time in ways that enhance their environmental fitness, and in a way that's analogous to (though certainly not identical with) the way biological organisms do. The question then is, in light of the previous post, what model better explains this phenomenon, the Darwinian or the Lamarckian?
Many people might be inclined, in this case, to say Lamarckian, and it's easy to see why: culture is acquired, after all. Thus, if we take Lamarckism to be simply the notion that acquired characteristics are passed on to (inherited by) later generations, it seems natural to assume that this is the model to explain cultural evolution. But, as the previous post discussed, the Lamarckian model leaves the actual mechanism of adaptive change unexplained -- it seems, instead, to require that there be an agent able to determine what constitutes environmental fitness, and then generate the required adaptation. Still, while that may have been a problem for biological evolution, such a requirement might seem entirely in keeping with cultural evolution, since cultures, after all, are made up of agents -- namely, us. And aren't we smart enough to figure out what our environment demands, and then produce our own cultural adaptations?
My answer, in short, is no. I don't say that out of any disdain for human intelligence, though I do think that we have a long-standing, if understandable, tendency to exaggerate the specialness of our situation in that regard -- in our scientific age, this tendency might be seen as the secular equivalent of the religious tendency to see human beings as having a special relationship to the divine. But our "intelligence", such as it is, and whatever it is, has no more ability to lift us out of nature than our "soul" or "spirit" had or has. That means, among many other things, that we can't simply avoid the question of how culture changes by handing it off to the mysteriously transcendent processes of agency. We need, in other words, a way of grasping how change can come about without having to postulate an agent that can step out of itself, so to speak, apprehend what sort of change the environment requires, and then step back into itself and make that change.
And once again, a Darwinian model can provide just such mechanism, despite having to deal, in the case of cultural evolution, with acquired characteristics that are inheritable or transmissible. We can remove agency from the picture simply by assuming that there are incessant (daily, hourly) microchanges in an individual's cultural imprint, some of which are more "effective" than others and are consequently reinforced at the expense of the others. The changes themselves stem from the individual's daily, hourly, moment-by-moment encounter with the world, which is automatically incorporated into the individual's cultural imprint as fresh experiential content. The "effectiveness" of those changes refers to environmental feedback, and has two primary forms -- one in communicative encounters, in which the feedback always results in some degree of increased semantic alignment (in fact, this just is the transmission of culture); the other in planning or thinking about intentional or purposeful behavior in the world, in which the feedback pertains to the degree to which the change helped attain the purpose. The key point to note is that both change and feedback -- variation and selection -- are independent of the conscious will or purpose of the individual herself, just as they are in biological evolution. No agent necessary.
None of this is to deny that there is such a thing as "knowledge", of course. And that knowledge, to the extent that it's "true" (meaning, to the extent that it's effective), can certainly be used to help plan and guide cultural change, including individual change, in ways that are purposeful or agent-driven. But we can think of the knowledge contained in culture as representing the potential of that culture for change, much as the development of organs through use -- which Lamarck took to be representative of species change generally -- represents the potential inherent in a given species. But, just as true biological evolution, contra Lamarck, marks a change in species potential, so real cultural evolution as such, involving the summed result of a myriad microvariations and reinforcements over time and geography, pertains to changes in cultural potential, which is inherently outside of our control or agency. In the last five hundred years or so, it's true, we've developed a kind of meta-level of knowledge, called science, which, (along with its derivative, technology), is a systemization of the process of acquiring new knowledge -- and which quite obviously has revolutionized our global culture, expanding its potential for change by orders of magnitude. Nevertheless, nature itself -- to give a name to that impassive, implacable, indifferent environment -- remains outside of all cultural potential, no matter how potent it appears to us, and nature's judgment is final.