Random from Professing evolution column

From: bivalve (bivalve@mail.davidson.alumlink.com)
Date: Fri Feb 07 2003 - 14:08:46 EST

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    > Even where species changes in historic times have been clearly documented, no one has shown that the mutations responsible were random.<

    It depends on the definition of random. The occurence of mutations does fit a probabilistic model, as does the chance of a mutation, once it appears, of becoming established (through genetic drift). Likewise, some evolutionary trends appear to actually be mathematically described by random, probabilistic variation. A well-studied example comes from Dan Miller's work on muricid gastropods (the source of Tyrian purple dye). The first ones were relatively small and plain. Today, there are lots of big and spiny species. Is this directional evolution? Not necessarily. Because it is impossible to have fewer than zero spines, random variation in spine number will produce an increase in average and maximum spininess over time. Likewise, if the starting point was towards the small end of practical size for these snails, then random variation would produce an increase in average and maximum size. At certain times, there are abrupt shifts in the average, suggesting non-random!
     factors, but for most of their geologic history, they fit a gradually flattening bell curve with an absolute limit cutting off one part of the curve. However, if God is sovereign over the outcome of casting lots, as various passages attest, then this sort of randomness does not exclude God.

    In addition to such a mathematical definition, there is the looser sense Blake mentioned, where random is used to mean not readily predictable by humans. Chaotic systems are a good example-although they are mathematically constrained, we cannot predict detailed, long-term behavior. Some aspects of evolutionary patterns seem chaotic. Weather and multiobject gravitational systems are additional examples. Then there are the things that are not even mathematically constrained, such as the course of history, or of prehistory, e.g., which groups of Cambrian worms would be successful in the long term and which would not. Again, this is both an apparently accurate description of various aspects of evolution and of things that are said in the Bible to be under God's control.

    Finally, random is used in a metaphysical sense to mean purposeless or meaningless. Evolution is a description of biological processes and as such has no purpose or goal of its own, any more than gravity or other natural processes. However, this says nothing about whether God could be working out His purposes through the use of evolution.

    >Furthermore, there's the question of probabilities.... a sufficient number of favorable mutations ... in succession <

    Quantifying such probabilities is highly speculative. I do not think we can provide meaningful estimates at present, though it is possible to note factors that tend to raise or lower the probabilities.

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

    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


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