Re: Fw: Most popular/common dinosaur misconceptions

[don ohmes <d_ohmes@yahoo.com>]

See below. Thanks.

Don

----- Original Message ----
From: tholtz@geol.umd.edu
To: don ohmes <d_ohmes@yahoo.com>
Cc: keesey@gmail.com; dinosaur@usc.edu
Sent: Saturday, August 19, 2006 12:36:32 PM
Subject: Re: Fw: Most popular/common dinosaur misconceptions

>> OK. But germane to the thread is the question-- is this the universally
>> accepted definition of "dinosaur" among paleontologists?

>Essentially, yes. Some prefer other specifiers, but refer to the same clade.

Good to know.

>> Also--
>>
>>1). I accept that cladistics is useful, and understand the practical need
>>for simplifying assumptions, but feel that it is not certain (or even
>>likely) that Iguanodon and Megalosaurus could in reality be traced to a
>>_single_ parent organism, even if the entire historical record was in
>>hand.

>Ummm... So are you arguing for special creation, or for independant origin
>of different lineages of Terran life? 

No, and no.

>Because otherwise, any pair of
>organisms will have had some unique last population representing their
>most recent common ancestor, whether Meg. and Ig., you and fruitflies, or
>me and E. coli.

Yes. However, I feel that the boundary line of reproductive isolation, 
excepting unlikely cases of geographical isolation of a single breeding pair, 
is not bridged by one female (at least in higher animals). In other words, I 
believe that the "unique last population" of Iggy and Meggy, could it be 
analyzed, would likely be larger than one breeding pair. The "one species, one 
mother" is an excellent working hypothesis for creating trees, but I doubt that 
is how speciation usually occurs. Again, in higher animals. "Simple" stuff like 
E. coli and viruses, that's different. So me and E. coli may be linked by one 
female organism, even if I am correct. And yeah, I got a theory, er, 
hypothesis. But, WTFDIK? I wouldn't even know if it is, or was, novel. If 
anybody is interested, let me know...

>And of course everyone recognizes the chance of actually finding this
>population is vanishingly small. 

Might be undetectable, even if found?

>Nevertheless, the phrase is useful for
>heuristic purposes. See numerous discussions on this list in the 1990s.

Absolutely. And I will.

>> 2). The phrase "final common ancestor" seems to me to logically refer to
>> that magical Original Organism of "life arose at a single point" fame. Of
>> course, the reality of "single origin" is also quite uncertain.  If one
>> accepts that life could arise on other planets (ooops! undefined and
>> controversial term alert!), then logically one must accept that it _could_
>> have arisen more than once on Earth.

>Fair enough, but the evidence at present is more consistent with a single
>origin for all terrestrial life than multiple ones.

Agreed. In os, veritas. }: D

>> There could even have been exchange
>> of genetic information between lineages. Perhaps I could suggest "most
>> _recent_ common ancestor"?

>Actually, "most recent common ancestor" is by far the more common phrase.
>Keesey's terminology is far rarer.

Actually, I got "most recent" off the web.

        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