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Could meme evolution be conceptually similar to what has recently been discoverd about Prion evolution (see below)? What has troubled me in embracing the concept of a meme, is how the meme is structured (coded) in the brain, and what is the basis for the evolution of memes? I see memes as information entities, not physical entities, and the encoding and decoding of memes depends on the physical structure of stored information in the brain. As an information entity related to an initially very volitile physical structure (a new memory trace), they are very susceptible to degradation. Once fully integrated into a network of other information entities of long storage duration (both physically within the brain of an individual, and virtually in the collective (cultural) storage of a group), they are very resistent to degradation and any alteration. The prion is a physical entity (a protein of a specific 3D structure), but the the 3D structure is inherently a storage of information about the molecular structure of the protein constituents. Prion transmission appears to be by direct molecular / information interaction between a prionic protein, and a similarly structured non-prionic protein. Some proteins are highly susceptible to conversion, while others are highly resistent, with apparently intermediate categories. The intermediate categories are the ones that provide the substrate for evolutionary change in prions. Memes might similarly be characterized into types that are highly susceptible to evolution, and those highly resistent. Memes with a direct linkage to DNA actions (i.e., inherited) are highly resistent to change. New memes, memes not fully integrated into meme networks, or those with a weak physical substrate, are highly susceptible to change within an individual.
Yes, this is a big stretch but just thrown out for discussion. Actually, the prion probably has nothing to do with memes, but it did induce configuration changes in my meme meme.
Prions evolve without the benefit of DNA
The infectious proteins called prions show all the hallmarks of population genetics, even though they have no genetic material.

By John Timmer | Last updated January 4, 2010 8:10 AMText Size Print this article Leave a comment Prions, which cause diseases such as Creutzfeldt-Jakob and BSE (commonly called mad cow), are pretty scary stuff. They don't have any genetic material; instead, they're made from a protein that's normally produced by the brain. Like something out of science fiction, they adopt a distinct conformation, and then induce all the other proteins around them to adopt the same structure, gradually creating a tangle that's fatal to brain cells. Expose a healthy animal to the prions of a sick one, and the diseased form will gradually take over.

As if that weren't scary enough, evidence has been building that there are different strains of prions, presumably caused by slightly different protein structures, that vary in their ability to attack different hosts, the speed at which they progress, and their sensitivity to drugs that alter protein processing. New research published in Science shows that it's possible to convert one strain to another.

So, for example, the researchers were able to take a strain that was sensitive to a drug and grow it for a number of generations in the presence of the drug. A small fraction of the prions appear to be drug resistance at the start, and these become the majority after a number of generations. In the same way, it's possible to shift a population so it grows in better on different cells, or even better in cultured cells instead of the brain.

If all of that sounds familiar, it should—this is precisely the behavior we call evolution when it happens to a living organism or virus.

The researchers propose that there are a number (possibly more than a dozen) of low-energy potential prion structures that are separated by higher energy barriers. When a prion converts a normal protein, it typically forces it into the same structure as itself, but at a low probability, other variant structures result. The population of these variants can then expand or contract based on selective pressures.

Science, 2009. DOI: 10.1126/science.1183218