The picture they criticize is the picture I prefer - and I will respond to their critique. First, here is what they say:
One proposed solution to this puzzle is to consider the information, wherever stored, as the equivalent of the biological genotype, and the expression of the information in behaviours or artifacts as the equivalent of the biological phenotype (Dawkins 1976). The problem here is that it assumes that, when copying, we have access to a “cultural core” (Sperber and Claidière 2008), which represents the information/genotype, which we then use to build variable phenotypic expressions. This might be loosely the case: the classic example is the transmission of a recipe to cook, say, lasagne, where the recipe represents the transmitted, stable, genotype, and what you serve to your guests at dinner is the variable phenotype. However, in many cases, we do not have access to a “recipe”, but we extract the information from the result/phenotype (such as when we try to reproduce lasagne after tasting it at a friend’s home). Richerson and Boyd (2005) make a similar point when noting how the mental representations of different individuals who have tied the same bowline knot might in principle be very different. What is the genotype here? The individual, variable, mental representations of the bowline knot cannot be the genotype, as they are not, in general, transmitted, because they are different. For the same reason, the information stored in the artifact itself does not transfer directly in the (variable) mental representations.
In response I would deny the assumption at the end of the second sentence. The picture of genotype-as-inherited information and phenotype as genotype products does not assume that there's a "cultural core" - a recipe to be copied. Some of the "genotype" can go on to reside in the cake. The rule here is that it is germ-line if it is copied from.
I agree that this picture of the genotype/phenotype split is imperfect. However, the genotype/phenotype split is a very productive concept in many cultural and organic domains. IMO, putting the split between genotype-as-inherited information and phenotype as genotype products is the best place to put the divide. It works well in both organic and cultural evolution.
The rule that it is germ-line if it is copied from also seems fairly neat to me - by contrast with the idea that it is germ-line if it is the product of copying.
Blackmore (1999) wrote:
I will not, therefore, use the concept of the meme-phenotype because I cannot give it a clear and unambiguous meaning.
I claim that the picture of genotype-as-inherited information and phenotype as genotype products is both clear and unambiguous. It also happens to be the standard meaning of the concept - as far as I can tell.
IMO, the phenotype-genotype split is essential to both organic and cultural evolution. Trying to skip the distinction is a feeble cop-out. The issue is not whether to make a divide, but where to make it. Criticism of one proposal needs to be accompanied by a better proposal - if it is to cut any ice. This is where Acerbi and Mesoud don't really come through. They can see flaws in the proposal that I prefer - but they don't really have anything better to offer. Consequently, I think their criticism fails. Imperfections are not enough - critics need to have a better proposal.
Here's what they say next:
While this may appear pessimistic, we believe that pluralism in the conceptual definitions of the unit of analysis in cultural evolution is not a problem (see also Lymann and O’Brien 2003; O’Brien et al. 2010). Biologists, too, work simultaneously with multiple concepts of the ‘gene’, varying with context and use (Stotz and Griffiths 2004). Depending on various domains, and on the questions one is interested in, an opportunistic strategy can be the best choice.
Pluralism. Maybe. Of course the problem with pluralism is confusion and ambiguity. You can have a plurality of concepts without them clashing over terminology.
In the case of their example, 'gene' the main problem is the usage by molecular biologists. The term 'gene' belongs to evolutionary biology. The molecular biologists should simply abandon their claim on the word.