Re: [asa] New fruit fly threat in Southern California

From: Cameron Wybrow <>
Date: Wed Aug 05 2009 - 21:37:20 EDT


In many walks of life, it isn't necessary for pragmatic purposes to be able
to account for why certain characteristics are "bundled". It is only
necessary to notice that they frequently are. Farmers in olden days, long
before there was any physics-based science of climatology, often noticed
that certain weather tended to follow certain conditions, signs or events.
And of course they deduced) that if you don't have a cow to get milk from, a
goat was a more likely bet than a sheep to be an animal that was a good
"milker". And if I took a dog (of a breed unknown to me) for a walk, I
would not at all be surprised to see it head for trees and fire hydrants,
even though I don't have the slightest clue *why* dogs target trees and fire
hydrants. Certain associations, certain correlations, often provide
predictive power, even in the absence of theory.

On this "common sense" basis, it is not at all surprising that not just one
particular fruit fly, but even a whole genus or even family of fruit flies
(and remember that "genus" and "family" are categories than can be arrived
out without evolutionary presuppositions, e.g., Linnaeus) would employ
pheromones identical or very similar to those of another fruit fly. Even if
one had never heard of *either*
special creation *or* evolution, one would predict that. Critters that are
similar in many ways already known to us are likely (based on experience in
analogous cases) to be similar in ways not yet established by us.

Of course, you can say that such knowledge is knowledge of mere correlation,
and is not 100% reliable as a grounds of prediction. True. But neither are
putative evolutionary lineages. For one thing, the scientists who have
decided that X is closely related to Y in evolutionary terms may have made a
mistake -- scientists have been known to reverse themselves on such
judgments before. Second, even if the evolutionary relationship is correct,
the method won't be 100% reliable. Two species of fruit fly, though
evolutionarily close, *might* employ different pheromones. (You yourself
give a reason why this might happen, e.g., geographical proximity, and there
could be many other reasons.) So to be certain about the pheromones, one
would still have to do the tedious empirical work, i.e., round up samples of
the two fruit flies in question and extract and compare their pheromones, to
make sure they were identical, before investing tens of thousands of dollars
(or more) of public money in manufacturing artificial pheromones (if that
was the plan). In other words, the final scientific authority lies with the
empirical biologists, who determine what the pheromones in fact are, not
with the evolutionary biologists, who are limited to making an educated
guess what they probably will be.

So what is the importance of evolutionary biology in the case of a fruit fly
infestation? At the most, it might be useful to point the empirical
biologists in the right direction, by saying to them: "The Punjabi
orange-striped fruit fly belongs to the same genus as the Californian
red-checked fruit fly, so it may well employ the same pheromones".
(Evolutionary biology would then be in the position of the general
practitioner who has a suspicion, but not the competence to check it out,
that a patient has cancer, and so recommends the patient to an oncologist.)
But if the only obvious difference between the two fruit flies were orange
stripes versus red checks, if in every other way the two fruit flies seemed
identical, the empirical biologists would be likely to do a pheromone check
anyway. (Just as patients who notice that they have several signs of cancer
will suspect it even before the G.P. broaches the possibility.) I therefore
maintain that evolutionary biology's usefulness in such practical matters is
greatly exaggerated. I think the biochemists and agricultural biologists
would generally know what to do without ever cracking open their volumes of
Darwin or Mayr or Dobzhansky.

I am not saying that a scientific theory has no value unless it has
practical applications. Newton's celestial mechanics had no applications
(e.g., satellite coverage of the Olympics) in his day, but it was still
rightly accepted as good science. Even if Darwinian macroevolution had
exactly zero practical applications it could be good science. I'm just
saying it's a foolish tactic for Darwinists to "over-sell" evolutionary
theory on the basis of its purported practical applications; stretching a
point on practical matters will only make Darwinian theory look desperate
for approval. I think the Darwinians should concentrate on strengthening
the theory *as theory*, i.e., should start providing plausible genetic
mechanisms for specific major changes. That is the route to public respect
for Darwinian theory, not allegations of practical applications which can be
arrived at just as easily without employing Darwinian theory, by plain old
common sense.

As for avoiding confusion, in the example we were discussing, the working
hypothesis was that the new fruit fly was an invader from far overseas, so
under normal circumstances the two fruit flies would not live near each
other. There would be no theoretical reason, therefore, not to predict
similar pheromones. But of course your point here reminds us of the almost
infinite elasticity of Darwinian explanation, because of the almost infinite
breadth of "mutation" and "natural selection" as categories of explanation.
According to Darwinian theory, we *would* expect fruit flies of similar
lineage to have similar pheromones, except when we *wouldn't* (because of
geographical proximity or some other reason); we *would* expect that
evolution would make human beings aggressive and selfish, to promote their
individual "selfish genes", except when we *wouldn't* (because of the
alleged advantage of compassion for *group* survival); etc. Because
Darwinian theory is so flexible, it is very hard what to say could falsify
it. When discussing "natural selection", one can always imagine local
circumstances which can "explain" why an unfulfilled prediction of the
theory doesn't apply (and therefore doesn't count as falsifying the theory).
Those who work in other sciences, where so much "wiggle room" is not
available to theories, may well be understandably skeptical of Darwinian
selectionist narratives.


----- Original Message -----
From: "David Campbell" <>
To: "asa" <>
Sent: Wednesday, August 05, 2009 6:32 PM
Subject: Re: [asa] New fruit fly threat in Southern California

>>> One of David's examples below provides another example of how
>>> evolutionary
>>> theorizing can *look* as if it contributes substantially to biological
>>> theory or practice while *in fact* being merely a redundant interpretive
>>> gloss.
> On the contrary, evolutionary models provide a reason for supposing
> that species that are presumed to be close relatives based on one set
> of data are likely to be similar in other features. (It would be
> possible to develop a non-evolutionary model with a similar
> prediction, though I can't immediately come up with one that isn't
> reducible to "the designer made things to look as though they
> evolved.")
> If the similarities were merely common constraints imposed by
> necessity on separately designed organisms, then there would be no
> reason to suppose that other features, not subject to the same
> constraints, would show the same resemblances. For example, a
> phylogenetic analysis of the flies based on cox1 genes (a
> mitochondrial protein) has no known reason to correspond to
> similarities in pheromones, except common ancestry. In fact, it would
> generally be advantageous for different species of similar flies that
> live near each other to have different pheromones to avoid confusion.
> --
> 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 Wed Aug 5 21:39:52 2009

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