Sunday, 13 August 2017

Mutations and recombination in cultural evolution

Another claim in the recent Creanzaa, Kolodny and Feldman document (Cultural evolutionary theory: How culture evolves and why it matters) is my topic today. They say:

Unlike in genetics, where mutations are the source of new traits, cultural innovations can occur via multiple processes and at multiple scales
To start with, this is rather obviously not true: classically, mutations and recombination are the source of new traits in evolutionary theory. However, are the authors correct to claim that these processes need augmenting in cultural evolution? The answer, I think is: not if you conceive of them properly in the first place. Let me explain.

To start with, let's look at what the authors claim are the new processes that go beyond mutation in the cultural domain. They give two examples. One is individual trial-and-error learning. They also say that:

New cultural traits can also originate when existing traits are combined in novel ways
This is cultural recombination - the parallel in cultural evolution of recombination in the organic realm. Do the authors really not know that ideas have sex too?

What about trial-and-error learning, though? Surely there is no leaning in genetics. Trial-and-error learning is a composite process. It starts with trials, which are often mutations of previous trials. Then there is the "error" part, which does not involve generating new variation at all, but rather is based on discarding information based on its success. In other words, it is selection, not mutation or recombination. By breaking trial-and-error learning down into its component parts, it is found to be a composite product of mutation, recombination and selection - not some entirely new process demanding fundamental additions to evolutionary theory. Skinner realised this, by formulating his learning theory while using evolutionary terminology (such as "extinction"). Many others have followed in his footsteps, conceiving of learning in evolutionary terms.

Isn't this a matter of terminology? With these author's definition of 'mutation' they are right, but with my definition of 'mutation', I am right? Yes, but terminology isn't a case of words meaning whatever you want them to mean. Scientific terminology should carve nature at the joints. Definitions of 'mutation' and 'recombination' that apply equally to both organic and cultural evolution are useful, I submit. Less general ones are not so useful.

To summarize, it is possible to conceive of mutation and recombination in a way that make them encompass all sources of variation. Mutations are sources of variation based on one piece of inherited information. Recombination is a source of variation based on two-or-more pieces of inherited information. In theory, it might appear that there's one other possible process: creation - variation based in inherited inforation which comes out of nowhere. One might give the origin of life as an example of genes arising from non-genes. However, we don't really need this proposed 'creation' process. Information never really comes out of nowhere. There's a law of conservation of information - parallel to the laws of conservation of energy and conservation of charge. We can see this in the microsopic reversibility of physics - information is neither created nor destroyed.

I claim then, that mutation and recombination have it covered. The additions to evolutionary theory proposed by these authors are not necessary. They are unnecessaary complications, which evolutionary biologists should soundly reject as not contributing anything to the basic theory.

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