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The Mystery of the Genome
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Figure 10a.
Crow’s mutations. At my request, Walter ReMine has kindly developed software for doing numerical simulations of Dr. Crow’s model of “truncation selection based on mutation count”. The curve shown above plots average number of mutations accumulated per person, after (n) generations – assuming sexual recombination, 100 individuals in the population, 100 mutations per person, 4 offspring per female, 25% nongenetic (random) elimination, and 50% selective elimination of the remainder, per generation. Although the rate of mutation accumulation eventually begins to level off, this does not happen until very serious genetic damage has been done. Given a more realistic model, there is no reason to expect the mutation count to level off. Crow’s model is designed to make the problem of mutation accumulation “go away”. It assumes all mutations have equal value, are all individually very subtle, yet none are so subtle as to be “nearly neutral”, that all selection is based upon “mutation count”, and that artificial “truncation selection” is operational. None of these assumptions are even remotely reasonable. Even though all these assumptions are artificial and unreasonable, the numerical simulation still shows severe mutation accumulation. Almost identical mutation accumulation curves have been modeled by Schoen et al., 1998.