The essential difference between MAs and GAs is the extra local search. This is supposed to be analogous to the ability of a martial arts master to make not random changes to his/her memes (genetic mutations are random), but directed changes. There are two problems with this:
In MAs, the hill-climbing does, in all cases I have seen, boil down to using random mutations and discarding the bad ones. (How else would we do hill-climbing, on a black-box fitness function?)
That is an easy question. A "black-box fitness function" doesn't mean the function is completely unknown. One is allowed to presume Occam's razor. That means that a range of techniques are likely to work when designing the next generation of trials: linear interpolation, extrapolation, fourier analysis of the fitness landscape - and so on. You can also keep historical records of notable past successes and failures - to help guide your search, use inductive inference, and take advantage of the rest of standard scientific toolkit.
I think there is a lot more to the idea of memes than just directed changes. What about their non-particulate nature, in Dawkins' phrase? That has no analogue in MAs that is not already in GAs.
Well that's because there are already analog genetic algorithms - or at least real-valued ones - which are about as "non-particulate" as you can get while remaining inside a digital computer.
To simulate cultural evolution some of the more important things you need are individual learning and social learning in a population. Much depends on how good your learning algorithms are. Yes, there are other aspects of cultural evolution - but if we knew how to reproduce them all in machines, we would have advanced machine intelligence by now. Today's memetic algorithms are necessarily a work in progress. However, the goal of simulating cultural evolution - and taking advantage of its obvious power - was the aim from the very beginning.
"All models are wrong, but some are useful" — George E. P. Box
As a student of linguistics, I’ve run into the idea of a meme quite a lot. I’ve even looked into some of the proposed mathematical models for how they transmit across generations.
And it certainly is a compelling idea, not least because the potential for modeling cultural evolution alone is incredible. But while I was researching the idea (and admittedly, this was some time ago; I could well be out of date) I never once saw a test of the model. Oh, there were several proposed applications, and a few people were playing around with models borrowed from population genetics, but I saw no proof of concept.
This became more of a problem when I tried to make the idea pay rent. I don’t think anyone disputes that ideas, behaviors, etc. are transmitted across and within generations, or that these ideas, behaviors, etc. change over time. As I understand it, though, memetics argues that these ideas and behaviors change over time in a pattern analogous to the way that genes change.
The most obvious problem with this is that genes can be broken down into discrete units. What’s the fundamental unit of an idea? Of course, in a sense, we could think of the idea as discrete, if we look at the neural pattern it’s being stored as. This exact pattern is not necessarily transmitted through whatever channel(s) you’re using to communicate it — the pattern that forms in someone else’s brain could be different. But having a mechanism of reproduction isn’t so important as showing a pattern to the results of that reproduction: after all, Darwin had no mechanism, and yet we think of him as one of the key figures in discovering evolution.
But I haven’t seen evidence for the assertion that memes change through time like genes. I have seen anecdotes and examples of ideas and behaviors that have spread through a culture, but no evidence that the pattern is the same. I haven’t even seen a clear way of identifying a meme, observing it’s reproduction, or tracking its offspring. Not so much as a study on the change of frequency of memes in an isolated population. Memetics today has less evidence than Darwin did when he started out; at least Darwin could point to discrete entities that were changing.
Without this sort of evidence, all the concept of a meme gives me is that ideas and behaviors can get transmitted, and that they can change. And I don’t need a new concept for that. Every now and then I’ll run a search on memetics just to see if anyone’s tried to address these problems — after all, a model describing how the frequency of ideas change in a population could be extremely useful to me — but so far I’ve seen nothing, and I don’t usually have the time to run a truly thorough search.
If any of you have, and if you know of evidence for the concept, please send me a link.