Eric Holloway on Dawkins’s dubious weasel

Dawkins has successfully reduced a combinatorial explosion to a manageable problem…or has he?:

In Richard Dawkins’ book, The Blind Watchmaker, he proposed a famous (and infamous) computer program to demonstrate the power of cumulative selection, known as the “Weasel program.” The program demonstrates that by varying a single letter at a time, it is possible to rapidly evolve a coherent English sentence from a string of gibberish…

Many have latched onto this program to defend (see here, here, and here) and debunk (see here and here) Darwinian evolution. On the other hand, Dawkins claims he only meant the program to show how natural selection can speed up evolution, and nothing further.

I think Dawkins’ program can indeed show something further, which is that natural selection can also make evolution impossible. What’s that again? That’s right: Dawkins’ weasel program shows natural selection prevents evolution from happening…

Multiplying the independent probabilities together, we end up with the probability of 2/27 * 2^-25 of hitting the target phrase, requiring more than 2^25 queries. This puts us right back into the combinatorial explosion Dawkins sought to avoid with piecewise selection. All I did was add a second target.

Eric Holloway, “Dawkins’ Dubious Double Weasel and the Combinatorial Cataclysm” at Mind Matters News

There was always something funny about Dawkins’s Weasel program. Did anyone ever really find the code?

Takehome: Eric Holloway shows that, far from demonstrating evolution, Dawkins’ weasel program shows that natural selection prevents evolution from happening.

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