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

Cameron:

Suppose we have an argument that proceeds according to

If A, then B.
A
then B.

Now supppose

D is logically equivalent to A.

Then we can argue equivalently

If D, then B
D
therefore, B

In this case, do we call D redundant in the same way that you have called
the evolutionary relationship redundant?

More explicitly, are some presuming that the statement
A: that two species are related in physiological, etc. ways.
and the statement
B: that two species are related evolutionary
are logically equivalent.

Now, in saying so, it ought to be clear that they are not. There surely
are cases of physiological, etc. similarity and a yet are said to not be
evolutionarily related.

It seems to me that there might be a distinction between evolutionarily
related and physiologically related. Suppose we have complete knowledge
of a given species, but imperfect knowledge of another one. In this case,
we may not be able to conclude from physiological, etc., similarity that
they are sufficiently related. But if we, for other reasons, had
concluded that they are evolutionarily related, then we might still
conclude, despite imperfect knowledge of physiology, that their pheremones
(and other biochemical characteristics) might be similar.

bill

On Tue, 4 Aug
2009, Cameron Wybrow wrote:

> 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.
>
> David suggests that if we don't know much about the fruit fly in question, we
> should turn to a close relative of the fly (where by close relative he means
> closely related in evolutionary terms) for which we have better information
> about pheromones, etc. The structure of David's argument is as follows:
>
> 1. In order to find out how to control Fly A (about which we know little)
> via a pheromone technique, we should apply our knowledge of the pheromones of
> a closely related fly (about which we know much more).
> 2. Evolutionary theory tells us that Fly B is closely related to Fly A.
> 3. Therefore, Fly B is a likely source of information about the pheromones
> which could help us to control fly A.
>
> It sounds logical. But wait: how did we determine that another species was
> "close in evolutionary terms" in the first place? Either we determined that
> by similarities in bodily form (morphology) or by similarities of some other
> kind (perhaps similarities in physiology, behaviour, or genetic make-up); or
> perhaps we determined it by a combination of similarities, e.g.,
> morphological plus genetic. This raises the question whether our *historical
> inference* (even if it is an *entirely correct* historical inference) that
> Fly B is "close in evolutionary terms" adds anything at all to our diagnosis
> and prescription. I contend that it does not, and that the "evolutionary"
> step is redundant, a mere interpretive gloss. In order to show this, let me
> write out all the steps in David's argument, including the implied as well as
> the stated ones:
>
> 1. In order to find out how to control Fly A (about which we know little)
> via a pheromone technique, we should apply our knowledge of the pheromones of
> a closely related fly (about which we know much more).
> 2. Fly B, which we know very well, has a lot of morphological,
> physiological, genetic, etc. similarities to Fly A.
> 3. Therefore, via the theory of evolution, Fly B is a close relative of Fly
> A.
> 4. Because they are closely related in evolutionary terms, Fly A and Fly B
> will have a lot of morphological, physiological, genetic, etc. similarities.
> 5. Therefore, Fly B is a likely source of information about the pheromones
> which could help us to control fly A.
>
> The redundancy of Steps 3 and 4 should be obvious, but if it isn't, it can be
> seen from another angle if we write out the argument as follows:
>
> 1. In order to find out how to control Fly A (about which we know little)
> via a pheromone technique, we should apply our knowledge of the pheromones of
> a closely related fly (about which we know much more).
> 2. By a "closely related fly", we understand a fly with very similar form
> and/or physiology and/or genetic make-up, and by these criteria, Fly B is
> closely related to Fly A.
> 3. Therefore, Fly B is a likely source of information about the pheromones
> which could help us to control fly A.
>
> Note that in the revised argument, all evolutionary language has been dropped
> ("closely related" being defined to mean "strongly similar in key relevant
> respects" rather than to imply any actual historical relationship). Yet,
> despite the dropping of all evolutionary language, the analysis and
> prescription of the problem *is exactly the same*. That is: "Find a fly
> whose characteristics you know very well that's a heck of a lot like the fly
> that's bothering you; there's a good chance that the two will have similar
> pheromones."
>
> A six-day literalist would thus come up with the same analysis and
> recommendation regarding the pheromone technique. ("If God made these two
> flies so very similar in so many ways, he probably gave them similar
> pheromones.") Why, then, do we need to know whether the two species are
> similar because they are close historical relations or because God used very
> similar engineering designs in their special creation? What practical
> difference does it make to the analysis and solution of the agricultural
> problem at hand?
>
> I am not concluding from this that six-day literalism is true, and that
> historical evolutionary relationships are false. I am not even concluding
> that six-day literalism is as plausible a theory as evolution. I am merely
> making the point that, *with regard to the biological problem set forth in
> the example we are discussing*, the statement that "Fly A and Fly B are close
> evolutionary relatives" is an optional gloss; we can only *know* that they
> are close evolutionary relatives *if we already know* their comparative
> morphology, genetics, etc. But *if we already* know their comparative
> morphology, genetics, etc., then we can guess that the pheromones in both
> species will be similar without the evolutionary inference.
>
> Why reason from A to B to D back to B and then to C, when one can reason
> directly from A to B to C? Why else, other than that evolutionary theorists
> must slip their interpretive gloss in as often as possible, even where it is
> redundant?
>
> Cameron.
>
>
> ----- Original Message ----- From: "David Campbell" <pleuronaia@gmail.com>
> To: "AmericanScientificAffiliation" <asa@calvin.edu>
> Sent: Sunday, August 02, 2009 5:46 PM
> Subject: Re: [asa] New fruit fly threat in Southern California
>
>
>>> I just read the following news item. Would you kindly get all the experts
>>> in evolutionary biology to solve this pending problem? However, they must
>>> solve the problem as evolutionary biologists not experimental biologists.
>>> <
>>
>> Obviously, to actually deal with the problem, you have to run the
>> experiment. However, evolutionary considerations can give us good
>> ideas about what could be good approaches (and bad ones).
>>
>> For example, reproduction is essential for an organism's success.
>> Reproductive cues are therefore likely, from an evolutionary
>> perspective, to be both fairly species-specific and strongly
>> attractive to the species. Although testing to make sure no
>> non-target species are also attracted, use of artificial pheromones to
>> attract the flies is likely to be one of the best approaches; a
>> similar approach is to swam the area with infertile mutant males to
>> reduce the odds of successful mating. (Additionally, my
>> brother-in-law can get paid to fly planes dumping out flies.)
>> Evolution also helps if the details for this fly have not been studied
>> (potential serious invasives not yet established in Western countries
>> are often poorly known). If so, we can look at close relatives to get
>> a good idea of the likely pheromones, etc. to greatly speed up the
>> search for what works against this fly. Conversely, it will help
>> identify what harmless local species might be most at risk as
>> non-target casualties.
>>
>> Another possibility would be to look for resistant crops. Those would
>> presumably be ones that evolved in contact with the pest species.
>> (However, the problem with the fly may merely be the fact that U.S.
>> consumers do not like maggots in their fruit, which would not be an
>> evolutionary threat to the plant.)
>>
>> Another possible control method would be searching for
>> predators/parasites of the pest. However, this has often been badly
>> mangled in the past, causing more trouble and often not controlling
>> the target pest. A control organism actually from the fly's home that
>> affects them, rather than something that attacks more or less similar
>> things somewhere else, would be better. Parasites are able to
>> specialize much more tightly than the average predator (in part
>> reflecting relative size of predator/parasite to prey), so they will
>> generally be a better model. Again, evolutionary considerations help
>> to know what non-target species you ought to test first.
>>
>> --
>> Dr. David Campbell
>> 425 Scientific Collections
>> University of Alabama
>> "I think of my happy condition, surrounded by acres of clams"
>>
>>
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>
>
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Received on Tue Aug 4 14:35:14 2009