How Life Defends Against Harmful Mutations 01/31/2002
Different populations have different ways of defending themselves against the destructive effects of harmful mutations, say David C. Krakauer of the Sante Fe Institute and Joshua B. Plotkin of Princeton, in a paper “Redundancy, antiredundancy, and the robustness of genomes” in the Jan 29 Proceedings of the National Academy of Sciences. Although presuming genetic mutations are a source of evolutionary novelty, they explain that damage must be guarded against.
The authors propose that small populations of large organisms (like mammals) use redundancy to maintain fitness: i.e., copies of genes and backup systems. But large populations of small organisms, like bacteria, appear to employ antiredundancy strategies: i.e., they are hypersensitive to mutation, but employ methods of removing harmful mutants:
“Assuming a cost of redundancy, we find that large populations will evolve antiredundant mechanisms for removing mutants and thereby bolster the robustness of wild-type genomes; whereas small populations will evolve redundancy to ensure that all individuals have a high chance of survival. We propose that antiredundancy is as important for developmental robustness as redundancy, and is an essential mechanism for ensuring tissue-level stability in complex multicellular organisms. We suggest that antiredundancy deserves greater attention in relation to cancer, mitochondrial disease, and virus infection.”
The authors propose a mathematical model for explaining the dynamics of redundancy and antiredundancy in differing populations. Populations exhibiting redundancy have hilly fitness landscapes with steep, narrow peaks. Antiredundant populations have a flat fitness landscape with small peaks, forming a “quasispecies” of mutants with similar fitness.
Although this paper is listed in the category “Evolution,” it is hard to see how it helps evolutionary theory. Whether a population is large or small, it works to shield itself from mutations and achieve stability. The fitness peak concept comes from graphing fitness as the vertical axis on a 3D plot of a population. Evolutionists have been realizing
[ever hear of Sewell Wright?] that fitness is not a progressive slope of “onward and upward” improvement
[this is written as if creationists have understood that fitness is not a measure of progress and improvement! ], but an undulating landscape with peaks and valleys. A population on a peak is stable, and would actually have to devolve to get off its peak and onto a higher one. This is not evolution in the Darwinian sense
[Okay, so I guess you haven't ever heard of Sewell Wright!] . It fits in better with the view that natural selection is a conservative process, allowing enough variation to compensate for contingencies (like mutations) that would otherwise destroy the population.
The authors do not describe how “evolutionary novelty” can become established, nor do they provide any example of a beneficial mutation. It appears, therefore, that this paper is promoting a view of life being in a state of dynamic equilibrium, not upward evolution.