Motivation no doubt did play a vital role in early human culture. It is not clear, however, how a mutation affecting some component of the motivational system could bring about the origin of culture.
Von Neumann  postulated that any self- replicating system consists of two parts: (1) uninterpreted information - a self-description that is passively copied to offspring, and (2) interpreted information - instructions on how to construct offspring. This turned out to be true of the genetic code; there are genes that provide instructions to the body on how to sustain itself, and genes that provide instructions for how, with the help of someone of the opposite sex, to create a child. But unlike genes, memes do not come prepackaged with instructions for their reproduction. They rely on the pattern- evolving machinery of their hosts' brains to create, select, and replicate them. Since we preferentially spread ideas that satisfy needs, our needs define viable niches for memes to evolve towards. As infants we might cry and kick no matter what need is most pressing, but as children we acquire and continually refine a repertoire of memes that, when implemented, satisfy various needs. We learn that reaching into the cookie jar satisfies one need, shouting "help" satisfies another, et cetera. Our memes, and the behavior they elicit, slide into need-defined attractors (regions of stability) in the memetic fitness landscape.
The fact that memes are not independently self- replicating does not prevent them from achieving reproductive success. In fact it may ironically work in their favor, because the cognitive machinery they depend upon not only actively manipulates them to produce "offspring-memes", but organizes them into a model of the world, or worldview, which it can use to figure out what to do whenever a situation is too complicated for its hardwired instincts. The worldview orchestrates behavior such that a meme gets implemented when it is likely to be useful, and that increases the probability that other hosts will consider it worthy of replication. This also means that there is a continuous coevolutionary interplay between pattern and landscape, which contributes to the often noted rapidity with which culture evolves.
Since many of our needs have a biological basis, e.g., the need for food and shelter, meme generation is largely constrained by our heritage as products of biological evolution. Thus the topology of the memetic fitness landscape largely echoes that of the biological fitness landscape. In the short term, the biological fitness landscape, and thus the memetic fitness landscape, fluctuates continuously as one need is satisfied and others take precedence (Hull , McFarland & Sibly , Gabora & Colgan , Maes ). For example, after eating, ideas that pertain to finding food are less likely. Over the lifetime of an individual, however, the set of biologically-based needs remains relatively constant. The trajectory of survival- motivated thought can be described as a limit cycle (periodic attractor) that moves through the set of stable memes whose implementations satisfy the various biological needs.
Variation-inducing operations restructure conceptual space and thus affect the memetic fitness landscape. Much as the evolution of rabbits created ecological niches for species that eat them and parasitize them, the invention of cars created cultural niches for gas stations, seat belts, and garage door openers. As one progresses from infanthood to maturity, and simple needs give way to increasingly complex needs, the stream of thought acquires the properties of a chaotic or strange attractor, which can be viewed as the formation of crevices in the original limit cycle. The landscape is fractal (i.e., there is statistical similarity under change of scale), in that the satisfaction of one need creates other needs - every crevice when examined closely reveals more crevices. This is analogous to the fractal distributions of species and vegetation patterns described by ecologists (Mandelbrot , Palmer , Scheuring & Riedi ). The endpoint of a cultural evolution trajectory turns out to be not just a point in multidimensional space, but a set of points with their own fitness metric - a "micro-landscape" in its own right. So although the memetic fitness landscape loosely follows the biological fitness landscape, there are places where it deviates, and this effect undoubtedly becomes more pronounced throughout an individual's lifetime. This means that the potential for meme diversity, though constrained by host need, is open-ended.
Or as "Bruno" put it (Gabora, unpublished ms.):
A lot of people in artificial intelligence are modeling how goals give rise to subgoals. The evolution of cars created niches for gas stations and seat belts and garage door openers. This is similar to how filling one ecological niche spawns other ecological niche - the evolution of cats created niches for species that eat cats and species that live in their guts as parasites. And it's a fractal process, in the sense that every time you examine one need, you realize that it can be decomposed into a set of subneeds, which themselves are decomposable into subneeds. Invariance with respect to scale. As the number of need-fulfilling objects increases, the utility of any one of them seems to decrease, until it reaches the state of absurdity it has reached in our society, where we make stuff like the strip of paper they put over toilets in fancy hotels to make it look like you're the first person who ever shit in them.
2. The role of motivation apparently did not come through as strongly in the target article, and am grateful to Prudkov for pointing this out. However, his statement that "One possibility is that the thought streams are independent of the system of motivations and that the activation of a basic drive is unnecessary to maintain them. This is Gabora's position." is surely a distortion, given that the example of abstraction I use throughout is explicitly derived from the NEED TO TRANSPORT WATER, and discussed in this context, e.g., "They could not retrieve the memory that an intestine is in the cave, much less realize it is relevant to the goal of transporting water" (paragraph 21). Prudkov claims "in other words, the first concept did not emerge at random, it arose from long-term and deliberate concentration on a particular problem". Though I may not have succeeded, this is exactly what I meant to convey through the example of the problem of water transport. Although Prudkov characterizes his view as "opposite" to mine, I think upon rereading my article, and the earlier one of which it is an elaboration, he will see that the two views are very compatible.
3. Prudkov claims that since the "memetic mind imposes no constraints on the associative stream of thought" it would be "chaotic". Again this is misleading. In paragraph 40, I write: "Selection comes in the form of drives, needs, attention-focusing mechanisms, and the associative organization of memory, which constrain how one meme evokes another." In paragraph 38 I go to great lengths to explain why streams of thought are not chaotic but rather at the proverbial edge of chaos.
4. Although I agree with Prudkov that motivation played an important role, I do not see how "changes in the motivational system" ALONE constitute a serious alternative explanation for the origin of culture to that proposed in the target article. Prudkov claims that "Perhaps from a genetic mutation, an early human began to use sticks as tools after an initial situation involving very high levels of activation conditioned by a basic drive." It is unclear how a heritable mutation affecting the motivational system would cause a human to use sticks as tools.
5. Finally, the clean separation Prudkov seems to draw between memory and thinking strikes me as odd; to me they are intimately entwined.
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