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[George, I am sure that I am not alone in my wish that you respond a minimal
number of times to each posting. Please consider this.]
At 09:57 PM 3/28/97 -0500, George Olshevsky wrote (quoting me):
>No, only if you think that cladistics has generated the correct phylogeny can
>you point out convergent characters, homologies, and so forth. The assumption
>that cladistics >must< generate the correct phylogeny is, however, certainly
>open to question.
That is absolute garbage. Cladistics has *NEVER* claimed to produce
the "correct" phylogeny. This is why a cladogram is called a pylogenetic
hypothesis. It is hubris to think that you could ever *know* the "correct"
character transformations [shared, derived characters, convergences,
etc...]. Cladistics *hypothesizes* a phylogeny, including the character
transformations. That's why I said "hypthetical tree". This is why
cladistics is *scientific*, it is falsifiable ("open to question" in your
If you think *you* have a "direct line to the tree of life" as Dr.
Holtz put it, please tell us.
> Consequently, so are any putatitve homologies and convergences.
Absolutely correct! My lord, have I finally gotten through to you?
Now my question is, again, do *you* think *your* character
transformations are not open to question?
>Let me construct an analogy that may clarify my personal stand on cladistics.
>In chess, computers can be programmed to examine billions of possible moves
[... ... ... ... ... ... ...]
>If winning a chess game is likened to arriving at a correct phylogeny, then
>cladistics is like brute-force chess algorithms, which win against most
>players most of the time.
Oh dear, oh dear, George is gonna go out and launch the Butlerian Jihad!
Wow, this is some impressive rhetoric. Of course cladistics is not
necessarily going to produce *the* actual phylogeny. It isn't expected to.
It simple produces the *most likely* phylogeny.
This is not at all like chess, which is a competitive interaction.
In this case, a competition between a machine which has been programmed to
perform in certain ways and a man who can think flexibly and presumably come
up with ways to fool the computer. But cladistics is not a competition of
man versus machine, it is an exploration of nature by man, using machines as
tools to clarify complex observations.
Your analogy only works if you compare nature to the grandmaster and
cladistics to the computer. In this case, you would be implying that nature
is out, willfully, to fool the cladist. This is, of course, nonsense, unless
you believe in a malevolent god trying to fool all scientists. "Nature" is a
complex set of interactions deriving from simple principles. Barring the
uncertainty present at very fine resolutions, nature is inherently knowable
(although this may be practically impossible). Thus nature may be likened to
the machine as well, and we get machine versus machine. The more we learn
about nature's machine, the better able we are to program ours to defeat it.
>And grandmaster chess represents those phylogenetic
>methods that go >beyond cladistics<, experience-based methods and principles
Experience is *only* as good as the framework in which it was
derived. Without a proper (phylogenetic) framework, how can we expect even
the most intelligent man to find the truth (I draw to your attention
Aristotle, Lamarck, Bowen, Gallileo, etc., all fine scientists who's
framework limited the application of their experience).
How good is an experience-based principle when the experience it is
based on is not necessarily valid. I cite "Cope's Law" as an example.
>that so far remain only vaguely articulated among evolutionary biologists. It
So, I am to take the inarticulate mumblings of one scholar over the
clear, reproducable results of twenty?
>is these principles that set off the warning bells when cladistics produces
>those startling or anomalous results.
These startling or anomolous results may very well be closer to the
actual phylogeny, but the "inarticulate biologists" you mention may not be
awarew of this possibility because their experience is rooted in the
fallacious concepts of an earlier mode of "eyeball phylogeny".
>For me, the grand theme of archosaurian phylogeny is BCF: the idea that
"'BCF', what's that?" :)
>There is no way to reach this
>paradigm--or its unshifted antithesis (BADD), for that matter--from
>cladistics or from direct analysis of known material.
So, when the material we know (our scientific observations) does not
support your theory, you attack the methods of scientific analysis itself. I
ask you, is this scientific?
By the way, cladistic analysis supports "BADD" as you call it.
Period. Don't say it doesn't. It may not explain *how*, but thaat is not
it's purpose, that is something left to the scientist performing the analysis.
>Rather, it is a unifying theme that accounts in a clean and simple way for a
>number of peculiar characters possessed by certain dinosaurs[...]
And acceptance of it over the current theoretical groundwork is
tantamount to the rejection of a scientific approach to the study of nature.
>If the problem is in BCF, I
>modify or discard the theme; but so far the problems seem to have lain with
Well, here, I've got a big problem for you: "BCF" DOES NOT FIT THE
FACTS BETTER THEN "BADD". Since the facts support "BADD", you need to modify
(unlikely, although I'd advocate it) or discard your entire theory.
>In BCF, for example, _Mononykus_ is simply a small theropod that retained a
>[...] We know this because it possesses a number of theropod
>characters lost in all avialan birds [...]
There is NOTHING wrong with reversals. They may have happened all
the time. You neglect to mention the characters it has *in common* with
>Too many reversals--too many characters reappearing
>in the same state they were in before being lost--set off loud warning bells
Because the individual looking at the situation has never heard of
neotony. Should I be surprised that the Hoatzen has claws in the same state
as when they were lost?
I especially find it amusing that when you are presented with
evidence that a reversal has occurred to a different state than that from
which it was lost (eg. the therizinosauroid inner toe), you balk.
>(loudness of bells is directly proportional to the number of reversals)
Perhaps you are in the wrong line. Theropod phylogeny could give you
a *real* headache.
>I move the branch with _Mononykus_ out of
>the avialan clade and farther back among the theropods, and soon the warning
>bells stop ringing.
Apparently you don't have a "convergence bell". May I suggest a
garage in your region which may be able to install one? :)
>So perhaps the principle here is: Do the cladistics, but if there is an
>unusual number of reversals (whatever that may mean), re-examine the
>characters and see whether moving the clade will make the worst of the
>reversals go away.
WHY? Why only reversals? How many is unusual? So, you don't advocate
tallying the relevant numbers of synapomorphies, but you do think the number
of reversals is significant? What is your basis for this claim? A hunch?
Reversals are, IMHO, potentially *more* likely than convergence, as
the gewnetic code for the primitive state is still present in the organism.
So why are you so afraid of them?
Cladistic analysis is simply a tool--a worthy tool but
>only one among several--for doing phylogeny.
It is a *scientifc* tool, and scientists use scientific tools.
Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock TX 79409
Web Page: http://faraday.clas.virginia.edu/~jrw6f