On Fri, 17 Sep 1999 16:12:03 EDT, Biochmborg@aol.com wrote:
[...]
KO>Before you go making blanket statements like those in the above paragraph,
>you might want to read the latest edition of Futuyma's _Evolutionary
>Biology_. Even the rather old edition I have (1979) contains many examples
>of direct empirical testing of "Darwinism" and other evolutionary
>alternatives. I understand how much you want to believe that "Darwinism" has
>somehow failed in scientific methodology, but that simply isn't true, and the
>more you stubbornly refuse to learn the truth, the more isolated you will
>become from those evolutionary scientists who might find your skepticism
>beneficial.
Johnson in "Darwin on Trial" dealt with Futuyma's "direct empirical testing
of `Darwinism'" in Futuyma's "Science on Trial: The Case for Evolution"
(1983):
"Douglas Futuyma has done the best job of marshalling the supporting
evidence, and here are the examples he gives of observations that confirm
the creative effectiveness of natural selection:
1. Bacteria naturally develop resistance to antibiotics, and insect pests
become resistant to insecticides, because of the differential survival of
mutant forms possessing the advantage of resistance.
2. In 1898 a severe storm in Massachusetts left hundreds of dead and dying
birds in its wake. Someone brought 136 exhausted sparrows to a scientist
named Bumpus, I imagine so they could be cared for, but Bumpus was
made of sterner stuff and killed the survivors to measure their skeletons.
He found that among male sparrows the larger birds had survived more
frequently than the smaller ones, even though the size differential was
relatively slight.
3. A drought in the Galapagos Islands in 1977 caused a shortage of the
small seeds on which finches feed. As a consequence these birds had to eat
larger seeds, which they usually ignore. After one generation there had
been so much mortality among the smaller finches, who could not easily eat
the larger seeds, that the average size of the birds (and especially their
beaks) went up appreciably. Futuyma comments: "Very possibly the birds
will evolve back to their previous state if the environment goes back to
normal, but we can see in this example what would happen if the birds
were forced to live in a consistently dry environment: they would evolve a
permanent adaptation to whatever kinds of seeds are consistently available.
This is natural selection in action, and it is not a matter of chance."
4. The allele (genetic state) responsible for sickle-cell anemia in African
populations is also associated with a trait that confers resistance to malaria.
Individuals who are totally free of the sickle-cell allele suffer high mortality
from malaria, and individuals who inherit the sickle-cell allele from both
parents tend to die early from anemia. Chances for survival are greatest
when the individual inherits the sickle-cell allele from one parent but not
the other, and so the trait is not bred out of the population. Futuyma
comments that the example shows not only that natural selection is
effective, but also that it is "an uncaring mechanical process."
5. Mice populations have been observed to cease reproducing and become
extinct when they are temporarily "flooded" by the spread of a gene which
causes sterility in the males.
6. Finally, Futuyma summarizes Kettlewell's famous observations of
"industrial melanism" in the peppered moth. When trees were darkened by
industrial smoke, dark-colored (melanic) moths became abundant because
predators had difficulty seeing them against the trees. When the trees
became lighter due to reduced air pollution, the lighter-colored moths had
the advantage. Kettlewell's observations showed in detail how the
prevailing color of moths changed along with the prevailing color of the
trees. Subsequent commentators have observed that the example shows
stability as well as cyclical change within a boundary, because the ability of
the species to survive in a changing environment is enhanced if it maintains
at all times a supply of both light and dark moths. If the light variety had
disappeared altogether during the years of dark trees, the species would
have been threatened with extinction when the trees lightened.
There are a few other examples in Futuyma's chapter, but I believe they are
meant as illustrations to show how Darwinism accounts for certain
anomalies like self-sacrificing behavior and the peacock's fan rather than as
additional examples of observations confirming the effect of natural
selection in producing change. If we take these six examples as the best
available observational evidence of natural selection, we can draw two
conclusions:
1. There is no reason to doubt that peculiar circumstances can sometimes
favor drug-resistant bacteria, or large birds as opposed to small ones, or
dark-colored moths as opposed to light-colored ones. In such
circumstances the population of drug-susceptible bacteria, small birds, and
light-colored moths may become reduced for some period of time, or as
long as the circumstances prevail.
2. None of the "proofs" provides any persuasive reason for believing that
natural selection can produce new species, new organs, or other major
changes, or even minor changes that are permanent. The sickle-cell anemia
case, for example, merely shows that in special circumstances an apparently
disadvantageous trait may not be eliminated from the population. That
larger birds have an advantage over smaller birds in high winds or droughts
has no tendency whatever to prove that similar factors caused birds to
come into existence in the first place. Very likely smaller birds have the
advantage in other circumstances, which explains why birds are not
continually becoming larger.
Pierre Grasse was as unimpressed by this kind of evidence as I am, and he
summarized his conclusions at the end of his chapter on evolution and
natural selection:
`The "evolution in action" of J. Huxley end other biologists is simply the
observation of demographic facts, local fluctuations of genotypes,
geographical distributions. Often the species concerned have remained
practically unchanged for hundreds of centuries! Fluctuation as a result of
circumstances, with prior modification of the genome, does not imply
evolution, and we have tangible proof of this in many panchronic species
[i.e. living fossils that remain unchanged for millions of years]....' Grasse
P.P., "Evolution of Living Organisms", Academic Press: New York, 1977,
p130).
This conclusion seems so obviously correct that it gives rise to another
problem. Why do other people, including experts whose intelligence and
intellectual integrity I respect, think that evidence of local population
fluctuations confirms the hypothesis that natural selection has the capacity
to work engineering marvels, to construct wonders like the eye and the
wing? Everyone who studies evolution knows that Kettlewell's peppered
moth experiment is the classic demonstration of the power of natural
selection and that Darwinists had to wait almost a century to see even this
modest confirmation of their central doctrine."
(Johnson P.E., "Darwin on Trial," [1991], InterVarsity Press: Downers
Grove Ill., Second Edition, 1993, pp25-27)
Steve
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"In considering the Origin of Species, it is quite conceivable that a
naturalist, reflecting on the mutual affinities of organic beings, on their
embryological relations, their geographical distribution, geological
succession, and other such facts, might come to the conclusion that species
had not been independently created, but had descended, like varieties, from
other species. Nevertheless, such a conclusion, even if well founded, would
be unsatisfactory, until it could be shown how the innumerable species
inhabiting this world have been modified, so as to acquire that perfection of
structure and coadaptation which justly excites our admiration." (Darwin C.R.,
"The Origin of Species by Means of Natural Selection", [1872], Everyman's
Library, J.M. Dent & Sons: London UK, 6th Edition, 1928, reprint, p18)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
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