Re: Essentialism and such (was a bunch of previous subject lines)

[dinoboygraphics@aol.com]

> > > But from a pragmatic level, essentialism & typism results in 
misleading science.  A case in point: many of the Feducciaries (for
those new to the list, check out the archives) seized on Welman's 
analysis of the brain of the coelophysoid formerlly called
_Syntarsus_ (I'm going to miss that name) as demonstration that birds 
did not evolve from dinosaurs. Why? Because the brain of
_Syntarsus_ was too different from birds. And since _Syntarsus_ was a 
theropod dinosaur, its brain represented the "theropod type",
and therefore theropod brains could not have been the origin of bird 
brains.<<<

Another example (this time from the light side of the force...) is the 
initial evaluation of Archeopteryxs CT scanned brain; it was trumpeted 
at SVP as being "very avian" and hence being evidence that 
Archaeopteryx was itself presumably very avian (e.g. a good flier, 
etc).  The problem is that Allosaurus and Coelophysis where the 
comparisons (again, representations of the theropod "type" brain); not 
a single maniraptoran or (other) basal avian was used to compare 
amongst the immediate in/out groups, so we have no idea how "birdlike" 
Archaeopteryx's brain was compared to its sister taxa.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: tholtz@geol.umd.edu
To: Carl@dondwiggins.com; DINOSAUR@usc.edu
Sent: Fri, 27 Oct 2006 7:07 AM
Subject: Essentialism and such (was a bunch of previous subject lines)

> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf 
Of
> Carl
> Sent: Thursday, October 26, 2006 8:47 PM
> To: dinosaur@usc.edu
> Subject: RE: Dinosaur a tecnical term; fish is not (was RE: Fish with
> milk (Sheesh spinoff))
>
>
> Elements are defined by their number of protons, and regardless of 
other
> variations, a given number of protons is _always_ the same for any
> example of that element, and anything having that number of protons is
> an example of that element regardless of its state.  So, in the sense
> that Webster and Goodwin mean it, the element has a universal and
> invariant essence at least as far as how we understand it.  This is 
true
> regardless of the time, space, historical background, or physical 
state
> of any particular example.

And herein lies one of the inherent (essential!) problem with using 
essentialism
in biology.

Organisms are NOT history independant! We are, every one of us, a 
record of
history. All protons are the same, each atom of a given
isotope identical in all aspects regardless of what happened to it 
before.

Not so with organisms, populations, and species. Our properties are 
highly
contingent on events of our personal and evolutionary
histories. No two of us are identical. ("There is variation in all 
populations"
being the first step in natural selection, after
all...).

But from a pragmatic level, essentialism & typism results in misleading 
science.
A case in point: many of the Feducciaries (for
those new to the list, check out the archives) seized on Welman's 
analysis of
the brain of the coelophysoid formerlly called
_Syntarsus_ (I'm going to miss that name) as demonstration that birds 
did not
evolve from dinosaurs. Why? Because the brain of
_Syntarsus_ was too different from birds. And since _Syntarsus_ was a 
theropod
dinosaur, its brain represented the "theropod type",
and therefore theropod brains could not have been the origin of bird 
brains.

This is hardly the only case of people using this sort of logic. It 
would make
sense if such "types" (NOTE: we are NOT talking
"holotypes" here!) were real, but instead they aren't. There isn't a 
"theropod"
type any more than there is a "dinosaur" type or a
"reptile" type. There is instead descent with modification.

Hope this helps,

       Thomas R. Holtz, Jr.
   Senior Lecturer, Vertebrate Paleontology
Department of Geology       Director, Earth, Life & Time Program
University of Maryland      College Park Scholars
   Mailing Address:
       Building 237, Room 1117
       College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661   Fax (CPS-ELT): 301-405-0796


________________________________________________________________________
Check out the new AOL.  Most comprehensive set of free safety and 
security tools, free access to millions of high-quality videos from 
across the web, free AOL Mail and more.