Saturday, 3 September 2011

Alex Mesoudi's take on memes

I tracked down Alex Mesoudi's take on memes. He describes memetics as being a "fad". In Cultural Evolution, page 42, he says:

Memetics makes the neo-Darwinian assumption that culture can be divided into discrete units that are inherited in a particulate fashion, like genes. It also assumes that memes are transmitted with high fidelity, this being one of the defining characteristics of a replicator according to Dawkins.

For me, this is disappointing material. Mesoudi fails to provide references. As far as I can tell, Dawkins did not, in fact, claim that high fidelity transmission was one of the defining characteristics of a replicator.

What Richard Dawkins actually says in The Selfish Gene (page 17) is:

A third characteristic of replicator molecules which would have been positively selected is accuracy of replication. If molecules of type X and type F last the same length of time and replicate at the same rate, but X makes a mistake on average every tenth replication while Y makes a mistake only every hundredth replication, Y will obviously become more numerous.

Dawkins clearly says that accuracy of replication is a trait of replicator molecules which is subject to positive selection. That means that the replicator molecules varied in their replication accuracy. This is completely the opposite of high fidelity transmission "being one of the defining characteristics of a replicator" - since it is saying that replicator molecules varied in their transmission fidelity and were subject to selection based on that variation.

Mesoudi is attributing to Dawkins the idea that high fidelity transmission is a defining characteristic of replicators - which is the opposite of what Dawkins said in The Selfish Gene. Dawkins went on to offer an explicit definition of the term "replicator" in The Extended Phenotype - and that doesn't include the concept of high-fidelity transmission either.

This material about memetics assuming high fidelity transmission appears to be F.U.D. As far as I can tell, the origin of it is a 1985 book on the topic - "Culture and the Evolutionary Process" by Robert Boyd and Peter Richerson. I figure they probably needed selling points for their variation of cultural evolution - and the ability to handle analog transmission was one of the ones they explicitly went for - on page 37. For that to be true, previous authors needed to have assumed discreteness. They took the conventional meaning of the word "replicator", and either failed to notice or ignored the fact that Dawkins (1982) had explicitly defined it as:

I define a replicator as anything in the universe of which copies are made.
In this definition, high fidelity transmission is conspicuous by its absence.

As far as I can tell, that is how the idea of high fidelity transmission is a defining characteristic of memes most likely arose. It is a rather sad story - but it is not clear why it is that this misunderstanding still being perpetuated some 26 years later.

Memetics doesn't require high fidelity transmission. The most successful memes do indeed exhibit high-fidelity transmission - just as Dawkins said. They have migrated onto the internet, where transmission is digital - resulting in hundreds of millions of bit-identical copies of the latest Lady Gaga song - but that doesn't mean that every single meme is transmitted with high fidelity. That would be ridiculous. The idea that high fidelity transmission is required by memetics is just a bunch of nonsense.

The researchers involved have been advised about this before. For example here:

In a section entitled “cultural variants are not replicators”, they repeat the false claim that copying must be perfect for a replicator to count as such

...and here:

Boyd and Richerson first introduce replicators as “material objects that are faithfully copied”. It certainly isn't Richard Dawkin's view who described replicators as “any entity in the universe of which copies are made”.

Also, I went on about this in my video review of Not By Genes Alone.

I will repeat the message again here: memetics does not require high fidelity data copying. The idea that it does is just a basic misunderstanding - originating - as far as I can tell with Boyd and Richerson, 1985, p.37. Their claim seems patronising to me. It is basic information theory that you can produce high fidelity information transmission (which is much more important for adaptive evolution) from low fidelity data transmission.

Boyd and Richerson were not attacking a straw man - since I actually have seen two people mess this point up:

  • John Maynard-Smith - In "Evolution-Natural and Artificial" (1999), John claims that adaptive evolution requires digital inheritance - and it makes some other rather silly claims for good measure. That is somewhat embarassing, but it has nothing to do with memetics - because Maynard-Smith was not a supporter.

  • David Hull - In "Science as a Process" (1988) David defined a replicator as being: "an entity which passes on its structure largely intact in successive replications."
Hull goes on to talk about entire populations passing on their structure "largely intact". What is "structure"? Hull says to see "Social Being" by Harre (1979) for more about that. However, I think this leaves only a little room for a sympathetic interpretation involving information since "information" and "structure" seem to be two rather different concepts. I think this puts David Hull's attempt to form a basis for evolutionary theory into the category of being wrong - or, at best, misleading.

Hull makes one passing mention of "memes" in "Science as a Process", on page 406. It is plain from his other writings that he endorsed the term. However, I do not endorse Hull's formulation. I think he made a mistake - or at least was being misleading. However, please don't attribute to memetics Hull's mistake. Lumsden and Wilson made some mistakes too, but I don't go around saying that gene-culture evoultion has got it all wrong.

The idea of high fidelity transmission is genuinely important for evolutionary theory - because information needs to be transmitted with high fidelity in large-scale culmulative adaptive evolution (with some caveats about incredibly strong selection pressures and mysterious sources of directed mutations). However it is possible to have high-fidelity information copying with low fidelity data transmission, as Shannon and Von Neumann previously explained long ago. We actually see such things in the modern world in the form of self-encrypting computer viruses. The data is wildly different in each generation, but the information is transmitted with high fidelity. So, it is high fidelity transmission of information - not data - from place to place that is the correct idea which associates the concept of "high fidelity" with the fundamentals of evolutionary theory.Also, not all of the transmitted information has to be conveyed with high fidelity, just some of it. You need some kind of mutual information between ancestors and descendants, or evolution is not going to be very "cumulative". There's a page with more details about this point here.

This is not a completely trivial point, and I can understand how people could get into a muddle about it. However, now that we have the internet, the time for getting into pointless muddles should be over.

I think the people from academia who persist in spreading this kind of material around need to be explicit about where they are getting it from, quoting chapter and verse. So far, there hasn't been very much of that. Boyd and Richerson (1985) cited "The Selfish Gene" and "The Extended Phenotype". Page numbers please. Boyd and Richerson (1985, p.266) pointed to the forward to "The Meme Machine". There Dawkins defends against the charge that cultural evolution does not have good enough fidelity to exhibit adaptations - which is a perfectly reasonable point to make. Dawkins has plenty of material in those books which flatly contradicts the alledged business about high fidelity copying - so I figure Boyd and Richerson can't have been trying very hard to find a sympathetic interpretation. If people remain incapable of quoting the incriminating chapters and verses, I figure they are eventually going to have to shut up about it.

In the mean time, please try to remember: neither genetics nor memetics requires high-fidelity data copying. The idea that they do is just a fallacy.

Memetics is the cultural sub-branch of genetics, which is defined as being the science of heredity. How inheritance takes place is an implementation detail in genetics and, similarly, it is an implementation detail in memetics. This should not be that difficult to understand.

As for memes being "discrete" and "inherited in a particulate fashion", it is just a matter of fact that memeplexes can sometimes get sliced up during transmission, just as geneplexes can, and - after being sliced - some heritable information is on one side of the slice and some of it is on the other - producing two or more "discrete" pieces - or "particles" - with potentially different pathways to immortality or oblivion.

Do memeplexes have preferred "break" points - rather like the grooves on a bar of chocolate? Sometimes they do, and sometimes they don't - and DNA sequences are much the same - occasionally there are preferred points of division (e.g. see restriction enzymes), but usually there are not - and the divisions that take place during meiosis can take place practically anywhere.

Hull (2001, p.120) addresses the "particulate" criticism, as follows:

Some authors argue that no general analysis of selection process equally applicable to biological and conceptual evolution is possible because genes are "particulate" while the units in conceptual replication are highly variable and far from discrete. In point of fact neither biological nor conceptual replicators are all that particulate. In both cases, the relative size of the entities that function either as replicators or as interactors is highly variable and their boundaries sometimes quite fuzzy.

Contrast this with Mesoudi (2011, p.46):

However, whereas genetic inheritance is particulate, cultural inheritance in many cases appears to be non-particulate.

In what senses is genetic inheritance particulate, though? In sexual creatures, nucleotide sequences can - and do - divide at practically any point. Yes, there are start and stop codons - but that takes us out of the realm of genetics and into the world of development. From a genetics perspective, about the only sense in which genes are "particulate" is that they don't divide half-way through a base pair. In summary, the supposed "particulate" nature of genetic inheritance is just nonsense. Organic genetic expression is somewhat particulate - at least if you can cope with ideas like "particles within particles" and "overlapping particles" - but genetic inheritance, not so much.

Dawkins clearly allowed for "non-particulate" replicators in his 1983 "Universal Darwinism" essay - saying:

A full science of Universal Darwinism might consider aspects of replicators transcending their detailed nature and the time scale over which they are copied. For instance, the extent to which they are "particulate" as opposed to "blending" probably has a more important bearing on evolution than their detailed molecular or physical nature.

Dawkins is presumably talking about recombination there. There is a difference between genetic and cultural evolution in terms of what types of recombination are permitted - with most genetic recombination being in the form of splicing, while memetic recombination can involve averaging, extrapolation and interpolation. Memetics has permitted these kinds of recombination from the beginning. There is no version of memetics that does not allow for "blending" recombination - except in form of straw men in the minds of critics.

Population memetics no more requires particulate memes than population genetics requires particulate genes. In both cases, it is the researcher who selects the boundaries of the entities whose frequency they are measuring.

From my perspective, the alleged "discrete" and "particulate" problems supposedly associated with memes represent more daft storms in a teacup.

Laland and Brown said that cultural evolution had been characteried by Sense and Nonsense - and I think that the "discrete" and "particulate" criticisms take us well into the "nonsense" territory.

These are not real problems but rather show all the signs of being marketing material concocted by rival researchers keen to find some way of distinguishing their own ideas from those of others that came before them with much the same notions.

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