Re: Protein Evolution

From: bivalve <bivalve@mail.davidson.alumlink.com>
Date: Thu Sep 09 2004 - 18:36:31 EDT

> I thought the list did not allow attachments, so I didn't do that. The link
> has additional links for PDF, but since I am at an institution with access
> to various journals, it might allow me whereas others cannot see it. Please
> clarify how I should post this if I need to.

It did not open the link for me; it does require a subscription or purchase of the article.
  
From the abstract, it is not obvious that the calculation takes either of two factors into account:
a) there are generally numerous ways to achieve a particular protein function
b) there are lots of genes to work with as possible starting points for mutation

A calculation not taking either of those into account has its uses. However, the abstract concludes no more than that the particular scenario under consideration requires large populations and/or large amounts of time to work. It cannot be used to conclude that evolution of a novel protein function is highly improbable.

Also, the evolution of novel protein functions involving multiple point mutations can happen in a reasonably short time frame under experimental conditions of artificial selection. I don't know the "population" sizes.

Another complicating factor may be the fact that a significant novel function in a protein may promote splitting of a population. E.g., mutation in an insect color gene changes its camouflage. Those with the new gene will survive better in a slightly different place than those with the old, thus strongly affecting the gene frequencies in the populations. The abstract mentioned eliminating selection for part of the model, but I don't know if it was factored in. Again, it's perfectly reasonable to derive a formula for the rate of gene frquency change without selective pressures, but it would be unreasonable to then claim that this calculation shows that things cannot change under a situation with strong selective pressure.

The wording of the abstract is a bit problematic. It says that in small populations, the time to fixation of a mutation "the time to fixation varies linearly with 1/N". In fact, the time to fixation increases with larger N (population size). E.g., in a population of 1, time to fixation is 0. I think the problem is in the abstract wording rather than a basic error in their calculation, but without the full text I can't tell just what they do mean.

As to the general phenomenon of scientific productivity of ID, there is also the problem of defining ID. This is a reasonable scientific paper written by people who favor ID and probably motivated by their ID views. However, it does not demonstrate ID, any more than providing an evolutionary explanation for a particular phenomenon refutes ID. It does raise some questions about the accusations of overwhelming bias among conventional scientists.

    Dr. David Campbell
    Old Seashells
    University of Alabama
    Biodiversity & Systematics
    Dept. Biological Sciences
    Box 870345
    Tuscaloosa, AL 35487-0345 USA
    bivalve@mail.davidson.alumlink.com

That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
Received on Thu, 09 Sep 2004 18:36:31 -0400

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