Re: Empirical evidence for evolution?

From: Chris Cogan (ccogan@telepath.com)
Date: Tue Jul 04 2000 - 00:00:30 EDT

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    At 11:52 AM 07/03/2000, you wrote:
    > >
    > >
    > >"Howard J. Van Till" wrote:
    > >
    > >Dear David,
    > >
    > >You wrote:
    > >
    > >> I here apologize for deviating somewhat from your original philosophical
    > >>string, but your mention that "the scientific concept of evolutionary
    > >>development [is] empirically warranted'' is so much on target with a
    > >>related interest of my own that I hope you might allow this intrusion.
    > >
    > >> Namely, I have for a number of years been seeking examples of verifiable
    > >>'empirical' evidence establishing biological evolution as 'scientific'
    > >>... but with little (no) success. Upon reading your above statement it
    > >>appears you may be aware of such evidence. Please do briefly describe
    > >>specific examples you feel properly qualifies as empirical evidence
    > >>confirming the reality of (macro) evolution to assist me in my search.
    > >
    > > Van Till replies:
    > >
    > > The whole of the body of scientific literature, along with the
    > >evaluation of that literature by persons whose training and experience
    > >qualifies them to do that evaluation, provides the warrant of which I
    > >speak.
    > >
    > >
    > > If you demand a short list of 'verifiable' examples--isolated from that
    > >whole body of scientific literature and its evaluation by the
    > >professional scientific community--that will suffice to convince a person
    > >who begins with a skeptical attitude, then you will probably be
    > >disappointed. It would be something like saying to a forest ranger, "I
    > >doubt that forests exist, but show me a tree that proves the existence of
    > >the forest and I'll believe in the existence of the forest." In reality,
    > >you just have to see a major portion of forest in order to gain a sense of
    > >what a forest is.
    > >
    > >Following is a list of some of my publications if you are interested in
    > >seeing more of my approach and what leads me to it. (List not shown for
    > >brevity...DAB)
    > >
    > >Cordially,
    > >
    > >Howard Van Till
    >
    >David Bradbury:
    >
    > >While I admire the semantic picture drawn by your 'tree' and 'forest'
    > >analogy, its really not all that appropriate. Indeed, on quick reading,
    > >it appears more misleading than informative. Would it not be a better fit
    > >to identify the skeptic as one well acquainted with 'trees' (from prior
    > >experience and textbook definitions), finding himself in the middle of a
    > >horizon to horizon grassland and being informed by a resident 'ranger'
    > >that he was surrounded by a 'forest'. Under these conditions, is it
    > >understandable and appropriate for him to ask the 'ranger' to please point
    > >out an example of what he considers a 'tree'?

    Susan
    >This is really a very cute trick. You say "I don't believe in forests,
    >please show me one tree." Then when you are shown several trees you say
    >"But this is only x trees, not a forest. It is obvious that forests do not
    >exist and you are (because of your atheism) concealing that fact."

    Chris
    Perhaps a better analogy would be someone who claims that trees don't grow;
    they just appear at whatever stage of growth they are found in. The person
    demands to see a tree grow, but stays in the forest for only a day or so,
    and then reports that he saw some minor variation in size of trees (called
    "micro-growth," but nothing that would convince him that trees can grow
    from a little sapling to a giant redwood (i.e., nothing that would convince
    him that "macro-growth" is a real fact of reality).

    If you point out to this person that the theory that trees *do* in fact
    engage in macro-growth explains the fact that we find trees in all stages
    of size, he will say, "I don't believe it. Where's the evidence? I think
    each tree is created in its current size, with the exception of small
    amounts of micro-growth."

    The person who objects to macroevolution is effectively making the same
    magical claim: That species are just created at whatever state they are
    found in, but they can vary slightly around some median form.

    Unfortunately, we *do* have examples of evolution that is beyond mere
    variation. We've already stayed in the forest too long, and have seen more
    than mere variational growth.

    Besides, the theory that species merely vary around a median assumes that
    there is a stable median around which to vary. There is no evidence of such
    stable medians, except where the environment *imposes* one by selecting out
    variations that go too far from the median. When the environment changes so
    that the current "median" is selected out and "deviations" from that median
    are allowed to survive, we get a new median, not merely variations on some
    Platonic ideal form for the species.

    There may be, in some cases, something like a semi-stable genetic median,
    if the reproductive process includes a process for correcting errors in the
    *parent* genome, but even such a mechanism would not be (and, indeed, could
    not be) perfect and perfectly reliable. Yet, it would *have* to be perfect,
    or macroevolution *would* occur.

    In other words, unless there is something to *prevent* macroevolution, it
    must occur.

    The question that opponents of naturalistic evolutionary theory must answer
    is: Just what is this mechanism that uniformly and perfectly prevents
    microevolutionary steps from accumulating to macroevolutionary levels? And:
    What is the evidence that such a mechanism even exists?



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