evolution as science

From: bivalve (bivalve@mail.davidson.alumlink.com)
Date: Fri Dec 07 2001 - 17:58:48 EST

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    I do not think that the definitions of evolution or of science
    being used here have all been made explicit, making
    communication a bit difficult.

    In general, biological systems are too complex for precise
    prediction, although probabilistic models can be given in
    many cases. This is also true of much of physics. Even a
    relatively straightforward system such as gravitational
    attraction between bodies becomes intractible if there are
    enough objects and enough time involved. Fluid dynamics
    become problematic with a much more restricted
    reference. It is simpler to predict the rate of establishment
    of mutations in a population than to predict details of
    eddies and currents in fluid flow. As noted in my previous
    post, it is also straightforward, though potentially
    time-consuming, to experimentally test the evolution of
    organisms in controlled settings. A range of predictions
    can be made and tested.

    Charting the course of evolution of organisms over
    geologic time, on the other hand, obviously requires
    historical evidence. This is subject to predictions that can
    be tested using the available evidence. For example, there
    is general agreement between the results of study of the
    fossil record and molecular comparisons. Another
    prediction that can be made and tested is that older rocks
    should generally have fewer modern forms and fewer
    complex organisms. The presence of transitional forms is
    another prediction of evolutionary theory confirmed by study
    of the fossil record. Functional constraints provide another
    evolutionary prediction that can be made. Stronger legs
    and feet are of great advantage for rapid terrestrial
    locomotion, and we can predict that organisms adapting to
    life in open areas will show locomotion-related evolutionary
    changes. We do not always have a way to predict whether
    a given lineage will specialize for leaping, bipedal running,
    or quadrupedal running. However, there are some strong
    phylogenetic trends, suggesting that structural and
    selective pressures play an important role. For hominids,
    the use of hands for grasping probably ruled out
    quadrupedal locomotion, and similar selective constraints
    would influence other lineages. Bipedal locomotion was
    the principle way of achieving more rapid locomotion in
    archosaurs; perhaps they are structurally well-suited for
    this approach. A good example of a prediction based on
    evolutionary theories and tested against the fossil record is
    Vermeij's idea of escalation and extinction. Predators and
    prey, or herbivores and plants, are in an evolutionary arms
    race. Over time, or in places with higher pressure, more
    defenses will evolve in the prey and new ways of
    circumventing them in the predator. This can be seen (or
    felt, as Vermeij is blind and came to the idea by his
    examination of shells from different regions) by
    comparison of modern habitats. Algae from the
    Indo-Pacific have levels of toxins high enough to deter most
    temperate grazers, yet are gobbled up by the tropical
    species used to such defenses. Extinction, however, may
    throw a wrench into the process. If you put lots of energy
    into building impenetrable defenses, you may not have
    enough energy left over to deal with environmental
    catastrophes. Thus, Vermeij predicted that the fossil
    record would have a cyclic pattern of increasing buildup of
    protective features, with crashes at times of major
    extinction. Examination of fossil faunas has provided
    mixed assessment of the idea so far.

    It should be emphasized, especially by Christians, that
    historical evidence is valid. It is not subject to experimental
    replication in some ways, but at least some aspects of the
    events can be replicated.

        Dr. David Campbell
        Old Seashells
        46860 Hilton Dr #1113
        Lexington Park MD 20653 USA

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