This discussion doesn't seem to be getting anywhere. Perhaps it would
be more helpful to provide my revision of Dobzhansky's statement:
Evolution is relevant to everything in biology, and everything in
biology makes sense as a coherent whole in light of evolution. Even
my research, which focuses on evolutionary questions, does not involve
thinking about evolution all the time. As I do the lab work, I need
to be focused more on doing the steps properly than on why. Carefully
documenting the morphology and molecular features of the mollusks
depends on factual reporting more than on evolutionary
considerations-"hey, that mussel has a funny-shaped flap and so does
that one, whereas those two have big bumps and a lot of little bumps,
and those two have a thick stripe on the gill." But when I try to
make sense of the pattern, I notice that they coincide with the
patterns in a gene involved in how mitochondria make energy and in the
DNA sequence for a spacer region between nuclear genes involved in RNA
translation. The coincidence makes sense in light of evolution, but
not in light of any non-evolutionary scenario that I have seen.
Of course, such evidence does not rule out a model like Behe's in
which there's a lot of evolution with some help as needed; the issue
there is whether the evidence indicates a need for help, evidence of
such having occurred, or a theological likelihood of it.
> I did not say that Linnaeus was "committed to the fixity of species". I
> did, however, imply that Linnaeus did not advocate an
> evolutionary view or base his biological thinking on such a view. If I am
> incorrect in this belief, please supply me with direct evidence that
> Linnaeus supported or advocated macroevolutionary views and that they
> affected the way he approached biological questions.
I intended to give a bit of a caveat, not particularly important to
the overall discussion. Linnaeus apparently did accept the idea that
species within a genus might have some more or less evolutionary
connection; there would have still been influence of ideas like the
chain of being as well, so trying to fit him into a modern
antievolutionary or evolutionary category would be anachronistic.
Overall he would probably come out fairly similar to the evolution
within a "kind" view found in some YEC and OEC circles. However,
based on somewhat limited data, he assigned chimps to Homo. Whether
or not this amount of evolution constitutes "macroevolution" or not is
open to debate.
> I did not say that "a priori" similar species ought to be chemically
> similar. I said that if species are similar in a lot of ways there is a
> good chance that they are biochemically similar as well. I granted fully
> that this might not be the case, that the inference was only one of
> probability, based on experience and common sense.
But why? There are also superficially similar species that are
chemically quite different. If you study them more closely, you can
find other features that point to greater difference. How do you know
what features are better or worse for predicting other similarity? On
the other hand, closely related species can be quite different in a
number of ways. Because we're built for walking and running, whereas
they're built for knuckle walking and climbing, humans and chimps are
quite divergent in many morphological features relative to some other
groups of organisms. Features that obviously respond to external
evolutionary pressures are likely to show convergence (e.g., shape of
fast swimming shark, bony fish, ichthyosaur, and dolphin). One
chemical similarity has no obvious a priori connection to many other
chemical similarities. If you observe enough of them, you might have
some empirical expectations, but no fundamental reason to back them
up. Furthermore, there is a consistent pattern of decreasing, but
still significant chemical similarity as you go farther and farther
away across organisms. Why should a nematode be biochemically enough
like humans to be a useful lab animal in studies relating to human
health? It's quite true that the people working at this university on
nematodes as model organisms don't care professionally about nematodes
nor why they work as models, and they have a very successful and
recognized research program. But if you ask the "why" type questions,
evolution gives the answer.
> In any case, as I made clear, Darwinian evolutionists cannot be sure that the two evolutionarily related species will be biochemically similar, either, so they have no advantage over the "common sense" approach in the pheromone-similarity-hunt that we were discussing.<
Not "no advantage", merely "no absolute guarentee of advantage".
> I spoke not of oranges and tennis balls but of oranges and tangerines. You
> know that I do not suppose that oranges
> and tennis balls are "alike" simply because they are round.
But they are alike-they are round, similar in size, and sometimes
similar in color.
> Give me credit for enough brains to distinguish the living from the non-living, please.<
As an illustration of my inclination to pedantics, the exact
delineation of living versus non-living is in fact quite problematic
getting into things like viruses. More to the point, why should
living things be more likely to be chemically similar than non-living
things? Tennis balls and living things are both composed of large
carbon-based molecules (the latter also have a lot of water). For a
plant example, why are osage oranges less like oranges than lemons
are? Osage oranges are round, with a bumpy surface, suggestive of an
overgrown underripe orange.
> Further, it was *you* who said in your last post that morphology (absent
> knowledge of the genome) is still the main factor driving evolutionary
> classification. And you *also* said that in the case of the fruit flies,
> evolutionary classification would be useful in predicting the biochemistry.
> So your argument implies that in many cases predictions about biochemistry
> would in fact be ultimately based on morphology. Now you are saying that
> morphology is unreliable as a guide to probable biochemistry? So then the
> evolutionary biologists would be making an unreliable guess about the
> pheromones? Then why do you think evolutionary biology would be so useful
> in such a case? Your logic escapes me.
Because evolutionary thinking helps us identify which morphological
and molecular features are likely to be better indicators of overall
similarity.
> So, tell us: since we are talking, ex hypothesi, about a fruit fly species
> for which we *don't* have detailed biochemical or genetic data, and since
> bodily form can't adequately distinguish the various fruit flies for
> evolutionary purposes, how on earth did you determine that our unknown fruit
> fly invader, X, was evolutionarily more closely related to weird-looking
> type A
> fruit fly than to the more visually similar type B fruit fly? Evolutionary
> classification must be based on *something*, and we've just ruled out
> genomics, biochemistry and morphology in this particular case. And fruit
> flies have no bones to be preserved, so the fossil record will be of no
> help. So tell me how your evolutionary biologists could have classified
> this new invasive fruit fly well enough to know what its evolutionary "close
> relatives" would be. I sense smoke and mirrors here.
Based on evolutionary studies, we know what features are better
indicators of overall similarity. Morphology is quite useful, but it
has to be examined in detail, with awareness of the evolutonary
patterns in the group, in order to figure out what are the best
features to look at. Actually, insects have decent fossil records-the
outer layer is tough, and by flying they can get into amber, lakes,
lagoons, and other good places to get fossilized. Nevertheless, I
don't think the fossil record gives us a real good phylogeny of fruit
flies. "These two flies look similar to me" is not going to be very
reliable, given that I am not an expert in fruit fly classification,
but someone who has carefully studied the morphology could give a
reliable suggestion of close relatives to study.
Of course, someone could look up current classification of fruit flies
and see what species are considered to be most similar, without
bothering to consider the evolutionary work that lay behind the
classification. But the classification had to come from somewhere.
>> But to know what the gene does and how it's supposed to work,
>> evolutionary data may be quite handy. In turn, this will help tell us
>> how to deal with the underlying genetic problem. Of course, the first
>> task is stopping the cancer, which depends on medical knowledge
>> (although discovering a cancer drug in species X should prompt study
>> of its close relatives to see if there are related useful compounds).
>> Cancer itself is something of an evolutionary situation, in which the
>> cancerous cells are evolving ways to dodge the body's controls while
>> the body tries to respond. Remembering that the cancer (or any
>> pathogen or parasite) is continually evolving is an important part of
>> maintaining medically relevant treatments. Cf. the Doonesbury cartoon
>> where the doctor asks the creationist patient whether he wants the
>> original drug or the ones that are effective against the strains that
>> have evolved resistance to the first drug.
>
> This paragraph equivocates on the meaning of "evolutionary situation". What
> you are calling evolutionary here is microevolution, which everybody grants.
Not exactly. Wells claims cancer is not caused by mutations, for
example. Moreover, the distinction that you are making between
microevolution and macroevolution is dubious. On the one hand, it is
true that one is not automatically obliged to accept full common
descent, etc. just because evolution clearly operates on some lower
levels. On the other hand, there is no fast line between the everyday
evolution within populations and the origination of new major kinds or
features. Furthermore, the line between "microevolution" and
"macroevolution" is drawn by ID, YEC, etc. at all levels, from "no
species can evolve into another species" to "full common descent, but
with some help from fine tuning or relatively rare miraculous
insertion of information." Thus, when someone claims to accept
"microevolution" but not 'macroevolution", what they mean is
ill-defined and probably more often than not includes rejection of the
sorts of speciation events that are regularly observed, given the
vigorous disparaging of "evolution" on the part of YEC and some ID.
> That cancer cells "evolve" in the way you are describing is non-contentious.
> And I grant your practical point, i.e., that doctors have to take into
> account the shifting behaviour of the cancer cells in their diagnosis and
> treatment. But that does not mean that they have to believe, e.g., that
> mammals evolved from reptiles via Darwinian means. It means only that they
> must grasp the genomics and biochemistry of cancer cells.
Then we do agree that evolution is useful and relevant to medicine.
The evolution of mammals from reptiles does have some consequences for
medicine, but much less immediate-more on the "why is the body
arranged this way", "why are this and that linked" type of questions
than "how to address this infection or cancer"
> And by the way, creationists are not so dumb as you make out. They
> understand perfectly well the fact of drug resistance.
Not dumb, but many are as careless as that, denying all "evolution".
The quality of popular antievolutionary material is generally
appalling, and few in the general public have given serious thought to
the immediate practical importance of evolution in pathogens.
> I am no creationist (in the narrow sense that you mean)
Not me-it's Trudeau's usage.
> In both these examples, you avoid specifying how we determine(d) what was
> "closely related". How did you determine, for example, that the parasite
> was "more closely related" to plants than animals, without employing genomic
> or biochemical data (which is forbidden by your original claim in the fruit
> fly case), and if morphological data is not reliable?
The work on Toxoplasma, including work by people at Messiah College,
involves genomic data. But before the complete genome was sequenced
(it has been now), the similarities that they spotted suggested that
there would be additional similarities. More importantly, they
suggest that Toxoplasma will overall be more biochemically similar to
plants than to us, which suggests that herbicides that don't harm us
may be worth investigating to see what they do to Toxoplasma, even if
we don't have the molecular mechanisms fully characterized (either of
Toxoplasma or the chemical).
> What you need to show me is that evolutionary classification gives some
> predictive power *that is not directly derivable from the criteria you used
> to do the classifying in the first place*. I claim (though I am willing to
> change my view if evidence is provided) that ultimately evolutionary
> classification in itself has little or no predictive power, but depends on
> other comparisons (morphological, genomic, physiological, etc.), which in
> themselves do have predictive power. In a word, evolutionary classification
> is an interpretive gloss of little or no technological value.
Instead of writing long posts to the ASA list, I ought to be working
on, among others, a paper on Juga, a genus of freshwater snails from
the northwestern U.S. I have DNA sequences from several populations
(one or two mitochondrial genes). Classification has been based
mostly on shell sculpture, but there are some problems (changing
sculpture with growth; is weak sculpture closer to smooth or to
strong, etc.). Species and subgenera are currently treated as
widespread. However, when I analyze the gene sequences using an
evolutionary model, several patterns stand out:
Although things with similar sculpture are often close in molecules,
relatively smooth shells turn up in many different groups (other
features, such as soft anatomy, provide useful characters).
Similarity in sequence correlates closely with where you are, although
the complex geologic history means that sometimes the connections
match past rather than present connections. (E.g., at a large scale,
they are more similar to east Asian forms than eastern North American
forms).
Molecular differences generally delimit populations from relatively
small areas. In turn, these group into several (usually multispecies)
groups that are also geographically circumscribed.
Thus, based on evolutionary considerations, I can predict something
about unstudied Juga populations. I am trying to get DNA from some
additional populations south of the ones I have data for. If they
finally cooperate, Juga from the American River will probably
genetically most similar to the smooth-shelled forms from the Pit
River and immediately south of it (Feather headwaters, Battle Creek)
rather than to those to the northwest or those to the west of the
Sacramento system.
There's nothing conspicuously different about the lifestyle of species
that occur in the American River versus the Klamath or Umpqua or
Columbia, or even some of the eastern North American forms; some of
the eastern North American ones can be confused with the western ones
in shell form, too. Why should the American River taxa be more
similar chemically to the ones in the Pit, except for evolutonary
reasons?
More fundamentally, the request "What you need to show me is that
evolutionary classification gives some predictive power *that is not
directly derivable from the criteria you used to do the classifying in
the first place*. " is fundamentally impractical for anything, not
merely evolution. Nothing predicted by any theory is not ultimately
derivable from the data that are used to generate the theory.
Theories provide general frameworks for data, and often point to
unexpected implications, but they are based on the data, and one could
always say "here's a pattern in the data that I expect to find in
other things" without explicitly formulating a theory.
> I agree with you about the need for theory in engineering. But in
> engineering, the theory is directly relevant to diagnosis and practical
> solutions. Biochemistry is like engineering as well. That is why
> biochemistry is so useful to medicine.
Although biochemistry is based on chemistry and ultimately on atomic
theory, in practice there's relatively little direct use of atomic
theory in biochemistry. There's a lot of empirical data involved, and
often the system of interest is too complex to adequately reduce down
to individual atoms.
> More generally, for a science to have technological applications, it must be able to predict *future* events.
Not merely that, it must predict future events of interest to
technology. Evolution can provide prediction about future events (as
well as about future discoveries relevant to past events, e.g. new
fossils or the results of new biochemical or morphological studies),
but systems of interest are rarely simple enough for straightforward
prediction, in contrast to many cases with physical laws.
> I agree with your complaints about many of these things. However, the hard
> fact is that none of these things seems to apply to electrical theory,
> Newtonian physics, etc., etc. The general public accepts 95% of the science
> which is taught in high schools without reservation.
There is less direct objection to most other areas of science
(exceptions include postmodernist fringe denial of any objective truth
as well as buying into incorrect alternative "science"), but still a
generally rotten grasp of them and a willingness to accept bogus
science such as astrology.
> And while I grant that
> religion plays a role in resistance to evolutionary theory, the truth is
> that physics and chemistry teachers are simply much better at answering
> questions -- and I'm talking about scientific questions, not theological
> questions -- to the satisfaction of students than biology teachers are (at
> least, when the biology teachers are teaching Darwinian evolution).
But many students are taught to be a priori dissatisfied with
evolutionary explanations and are not particularly paying attention to
the merits of the answers. Physics and chemistry get attacked, too,
when they are inconvenient for young earth or other favored claims.
> Darwinian explanations are always looser, less precise, with very little
> quantification (how many mutations would it take? how many years would it
> take? -- the biology teacher doesn't have the slightest idea), and the
> proposed mechanisms are of a broad, vague, non-specific kind ("drift",
> "mutation", "natural selection"), making them extremely elastic, and thus,
> when combined, capable of explaining virtually any possible outcome (X, the
> direct opposite of X, and every outcome in between), so that the theory
> seems oddly slippery.
Drift, mutation, and natural selection have very specific definitions
and several well-formulated mathematical models. However, the
situations of interest for evolution are inherently more complicated
than an introductory physics or chemistry problem.
> One thing that might help would be for evolutionary biologists to stop
> crowing about how great their theory is, and put in caveats showing
> intellectual humility and caution.
As a recent Science News pointed out with regard to physics, this is a
general problem in science (not to mention human endeavor generally).
Steve Gould commented favorably on our paper's disinclination to
assert that the results of our molecular phylogenetic analysis were
the authoritative last word, though in reality that reflected as much
our morphological backgrounds as any particular humility or, at that
point, enough experience with the vagaries of molecular analyses to
know what's solid or not. (Campbell DC, KT Hoekstra, and JG Carter.
1998. 18S ribosomal DNA and evolutionary relationships within the
Bivalvia. In P. A. Johnston and J. Haggart, eds. The Bivalvia: an Eon
of Evolution-Paleobiological Studies Honoring Norman D. Newell.
Calgary: Univ. Calgary Press, p. 75-85.; Gould's comment is in the
preface to the volume)
> (predictive *in the engineer's sense*, I mean; not in the weak sense that we
> would expect fossils like Tiktaalik, but in the strong sense that it can
> tell us what rabbits placed in the Amazon jungle will evolve into a hundred
> thousand years from now, as astronomers can tell us where Mars will be a
> hundred thousand years from now).
Although 100kyr is not enough to have significant uncertainty in the
position of Mars, it could be just about anywhere (apart from close to
the Sun on a galactic scale) in 4 billion years, including in the Sun,
collided with Earth, or ejected from the Solar System. The long-term
prospect of a gene with a known frequency in a population, with a
known degree of beneficial or negative selection, can be calculated as
well as the prospective position of Mars. Rabbits already live in the
Amazon and haven't changed all that much, so they probably won't do
anything dramatic over the next 100kyr-even if significant climate or
other environmental change occurs, there are rabbits in various
habitats, so the general body plan works OK. (Whether this particular
species is adaptable or not is an open question-several related taxa
are severely imperiled). Also, 100,000 years is not all that long,
evolutionarily. Make Mars or Antarctica, etc. habitable, add rabbits
but not a full suite of mammal types, and give it a few million years,
and the situation is much more interesting and hard to predict in
detail (not to mention de rest of de body).
-- Dr. David Campbell 425 Scientific Collections University of Alabama "I think of my happy condition, surrounded by acres of clams" To unsubscribe, send a message to majordomo@calvin.edu with "unsubscribe asa" (no quotes) as the body of the message.Received on Thu Aug 13 18:25:11 2009
This archive was generated by hypermail 2.1.8 : Thu Aug 13 2009 - 18:25:11 EDT