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Re: Cladistic taxonomy (was Dietary factors)

The $0.02 of a lurking philosopher:

Tim Williams wrote:
Ken Kinman wrote:
I'm afraid that there is a stalemate between cladists (who say birds
ARE dinosaurs) and the rest of us (who say birds are dinosaur descendants).

The distinction is purely semantic. Don't let Ken scare you. :-) It's all
much ado about nothing. A squall in a teacup.

When discussing tyrannosaurs or ceratosaurs with evolutionary biologists I
do not say "non-avian theropods". And I support the idea that birds evolved
from small theropods.


In written scientific correspondence, it helps to be explicit when
discussing one's ideas.  Hence the utility of such long-winded (and
admittedly cacophonic) terms as "non-avian dinosaur" (=Dinosauria of
traditional usage) or "non-cetacean cetartiodactyls" (=Artiodactyla of
traditional usage").

These terms facilitate the communication of ideas and concepts, leaving
little room for ambiguity. When someone writes "non-avian dinosaur" he or
she is letting it be known that a certain subset of a monophyletic group is
being excluded (such as for convenience). The reader does not have to pause
and wonder, "Does the writer mean _all_ dinosaurs, or is the writer
excluding _Archaeopteryx_ and other birds?".

I'm not a dinosaurologist, but I thought I'd insert a coupla more-or-less standard philosophical comments here, for what they are worth:

Convenience and ease of communication are important, but that doesn't mean that the points at issue are entirely semantic. Another (many would say more important) issue has to do with the real similarities and differences among the organisms in question. One thing, incidentally, that affects ease of communication is whether or not the available distinctions map easily onto the real differences among the things talked about. Some people think that's almost too obvious to even say; others think it's clearly wrong. Me, I dunno.


This is especially important for birds, since the delineation between birds and non-avian dinosaurs is entirely arbitrary. In effect, if a genus is more closely related to modern birds than _Archaeopteryx_, then it is considered a bird *in the scientific sense*. We (as humans) draw the line under _Archaeopteryx_. But Nature makes no such clear distinctions. The transition from "reptile" to "bird" (or from non-avian theropod to avian) essentially means the acquisition of one or two extra characters.

O.k., but that doesn't mean that the distinction between birds and non-avian dino.s is "entirely arbitrary". A lack of *clear* boundaries doesn't mean that there are no real similarities and differences...though these may be difficult to represent linguistically. That's why it's often handy to have a system of overlapping distinctions that group things in lots of different ways. But *lots* of non-arbitrary groupings is different than nothing but arbitrary groupings...

Bas VanFraassen sez: you don't need clear boundaries to have a legitimate distinction; all you need is a clear case of the one kinda thing and a clear case of the other kinda thing.

Classifications are an attempt on the part of humankind to impose a system on nature.

Again I note, on the verge of pedantry: at least some reasonable folks disagree with this. This, of course, sounds a lot like nominalism, the view that no two things are really any more similar to each other than they are to any other arbitrarily-selected thing... (e.g., a person is *really* no more similar to his identical twin than he is to a frozen water molecule in the Horsehead nebula). The nominalist holds that all "similarities" just result from us calling things by the same name. I just want to point out that that view isn't obviously true, and that the opposite view, realism, is *at least* as plausible. But I'm not sure you are really advocating nominalism, or even care about it...

We stick species in boxes, and label those boxes.
Linnaean classifications have tended to emphasise a gulf between Reptilia
and Aves.  Follow both lineages back in time, and (as the Spice Girls say)
"two become one".

Right, but that doesn't show that there isn't a real difference between reptiles and birds.

The difference between _Archaeopteryx_ and a crow
(or a
rooster, penguin, eagle etc) is far more than between _Archaeopteryx_ and
_Deinonychus_ (or _Velociraptor_, _Sinornithosaurus_ etc).

That suggests that our terminology is sub-optimal--but, again, not that there are no real differences among organisms.


It all comes down to a critical difference between _vernacular _ and _scientific_ communication. When I look up at a _Tyrannosaurus rex_ skeleton in a museum, I see a dinosaur. When I carve up a turkey on Thanksgiving, I see a bird.

Hey, now you sound like a *conceptualist*: differences depend on how humans happen to look at/think about things...

O.k....  I'm shutting up now...


p.s.  Hey!  My first post to the dinosaur list!  Woohoo!
If we believe absurdities  | All I say is by way of
we will commit atrocities. | discourse, and nothing by way
         -- Voltaire      | of advice.  I should not speak
                          | so boldly if it were my due
                          | to be believed.
                          |              -- Montaigne


William Max Knorpp
Dept. of Philosophy and Religion
James Madison University

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