Sunday, 18 January 2015

The minimum constraint on mutation

One criticism of Universal Darwinism is that the core principles it is based on - namely heredity, mutation and selection - are too general, are capable of explaining anything and therefore explain nothing.

This criticism was made, for example, in:

They say that the principles of:

variation, selection and inheritance [...] are but an empty hull that lacks own explanatory substance.
There's a sense in which this is true. The problem is with the "mutation" operation. Unconstrained mutation predicts everything and is useless.

Neo-Darwinism avoids this issue - by claiming that mutations are "undirected". However, this is not really an acceptable approach in cultural evolution - where it is widely agreed that mutations are not remotely random - and that modeling them as being "undirected" is a coarse and limited approach.

I generally attribute the correct resolution of this issue to Donald Campbell. He basically said that variation was generated on the basis of existing knowledge. He used the unfortunate term "blind" to describe this - which has led to endless misunderstandings of his idea by confused critics.

Gary Cziko's terminology from the title of his book, without miracles is another approach to the problem. The term "without miracles" expresses the idea that mutations should be explicable naturalistically. While naturalistic explanations are good, scientists normally take it for granted that their explanations should be plausible within a naturalistic framework. The idea that mutations do not involve "miracles" isn't really all that much of a constraint - and the more scientific theories constrain expectations the more valuable they are.

This article tries to answer the question of what the minimum constraints on mutation are that avoid the accusation that the resulting theory is vacuous. The answer is pretty simple: all that is necessary is that mutations should be limited. If an evolutionary sequence requires mutations that exceed the mutation limit, they violate the predictions made by the theory.

This constraint is even weaker than the requirement that mutations should be naturalistically plausible. On one hand the idea of mutations being limited (in some specified way) is vague and not very useful. However it does show how easy it is to avoid the accusation that Universal Darwinism is empty and vacuous. Just put a limit (any limit) on the type of mutations permitted by the theory, and you have a falsifiable theory.

1 comment:

  1. Yes, I also understand Donald Campbell to be correct on this. Darwinian processes operate by making small improvements, due to small variations, on existing structures. It provides for a gradual accumulation of knowledge rather than large jumps in knowledge.

    A truly random genetic mutations would reshuffle the genome which would guarantee extinction in a single generation. Instead it is the limiting of mutations through error correction of the copied genome which ensures that any mutations will be severely limited in scope.

    The same is true with the Darwinian process of science; small variations are made on successful existing theories and are judged by the evidence. Each generation of scientist goes through a long process of training in which they must learn the most successful existing theories to a high degree of accuracy. It is only then that they are in a position to offer small variations.

    John Campbell