Re: [asa] historical versus experimental sciences

From: David Campbell <>
Date: Mon Aug 24 2009 - 16:43:57 EDT

I agree with Cameron that there is, indeed, plenty of a priori
rejection of any "creationist" possibility in mainstream science. The
main difference between it and the "creationist" a priori rejection of
any "evolution" or "Darwinism" is that the a priori rejection of
"creationism" is usually accompanied by better science and therefore
is more likely to fool the scientifically informed but philosophically
weak, whereas the latter is generally superficially sounder on
religious issues.

This also produces some of what he complains of in the relatively
unsubstantiated assuming of an evolutionary explanation (e.g., in the
water strider leg paper). The average scientist takes evolution as
"of course everyone who's not some sort of religious crank knows that"
rather than as an area for active research, and the actual grasp of
evolutionary biology by other biologists is often weak.

Unfortunately, the most visible parts of ID and YEC vigorously
reinforce the impression that anything that might be called
"creationism" entails bad science.

The "creationism" in question for Hebert would be the idea of separate
creation of species, without regard to the age of the earth. While a
number of organisms do fit the pattern that Hebert describes, a number
do not, greatly weakening the case for some mysterious genetic
separation of species. Even the barcoding literature has reported
cases where very slight differences in cox1, rather than large
differences, characterize the apparent species, and a more general
examination of variation shows rather mixed results.

Back to my snails:
12 showed intraspecies variation of no more than about 0.5%, though
some are represented only by repeat samples from one population
(overall surveying of genetic variation within all the species was not
our goal). Five showed more than 1% maximum intraspecies variation
(though there could be sequencing mistakes, pseudogenes, or cryptic
species making this too high). Usually a difference of about 1.5%
corresponded to morphological and geographic differences large enough
to suspect separate species, but not always, and some
well-distinguished forms had less difference. Thus, the patterns are
not so clean-cut here.

Any evolutionary scenario expects somewhat lower variation within
species than between species. A strict neutral gradualism might
expect a full continuum. However, in reality several factors will
affect the distribution of alleles. Many of these can produce lower
diversity within a species than between them. One artificial factor is
that few studies thoroughly sample the entire range of a population,
so the intraspecies variation will typically be undersampled.
Population dynamics are another important factor. If the majority of
individuals descend ultimately from only a few females, then the
mitochondrial diversity will be lowered (ignoring most bivalves and
anything else with aberrant mt inheritance). In a small population,
much of the genetic diversity will be lost (bottlenecks, founder
effects, etc.). Selective pressure will affect any non-neutral

More generally, it is rather commonplace for people, including
scientists, to somewhat exaggerate how notable their
discovery/achievement/etc. is. This has been extensively exploited in
the game of "find quotes from evolutionists that seem to go against
evolution." I don't believe that you were out to misrepresent Hebert;
rather, I am invoking the genre as a large source of examples. The
people that do actively dig through the evolutionary literature in
search of things to misrepresent produce plenty of examples of
purportedly unexpected results that, on closer examination of the
original source, actually just say that "evolutionary mechanism a
turned out to be more important than evolutionary mechanism b" or
"previous studies were based on inadequate data" or other less
earth-shaking conclusion. It's like the Journal of Irreproducible
Results paper that noted that there are so many reports of new and
interesting species and suggested that a vast untouched field of
opportunity awaited anyone who tackled old and uninteresting species.

It is also true that the integration of genomic data into evolution is
at a relatively preliminary stage. We're in the midst (actually,
probably still near the beginning with regards to amount of data
generated) of a period of discovery and data generation. We need a
lot more data in order to tackle questions with the detail that
Cameron wants, although there are several examples where we can give
that type of information for specific points.

Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Mon Aug 24 16:44:53 2009

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