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Re: Archaeopteryx problem



At 05:14 AM 4/22/97 GMT, you wrote:
>On 20 Apr 97 15:42:00 EDT, www@cuinfo.cit.cornell.edu (ksjj@fast.net)
>wrote:
>
>
> Evolutionist like to assume that just because Archaeopteryx  appears
>to
> have shared some features with reptiles or dinosaurs it mean that it
> descended from a reptile or dinosaur.  Of course, there could be a
>problem
> with this thought concerning Archaeopteryx.
> Creatures often have similar features which evolutionists do not
>believe
> are derived from a common ancestor.   For instance, the giant panda
>and
> the red panda are similar enough to both be called pandas, down to
>their
> sesamoid thumbs (the only creatures to have them), but they are
>believed
> to have no close relationship.  The giant panda is believed to have
> descended from bears and the red panda from the racoon. The
>evolutionist
> call this evolution of their thumbs, "Convergent evolution"
> This process is said to have  made the thumbs of both pandas alike .
> If it can happen in that instance, on what basis does the
>evolutionist
> claim the so-called reptilian features of Archaeopteryx  prove
>descent
> from reptiles?

I'll try the short version.  For more details, read chapter 13 in Fastovsky
& Weishampel's The Evolution and Extinction of the Dinosaurs.

The short version: in convergent evolution, a few features might closely
resemble each other in disparate organisms, but the rest of the anatomy,
DNA, etc. will reveal the presence of discordant features (i.e., features
which demonstrate the actual ancestry of each of the different groups).

In Archaeopteryx, there are no (count them, no) features which are
discordant with a reptilian (specifically, dinosaurian) ancestry, and only a
couple of features which link it to more advanced birds.  This is not the
expectation for convergent evolution (which is still, of course, an example
of Darwinian evolution!), but is instead expected in a form transitional
between a more primitive generalized form and a more derived advanced form.

Hope this helps.

.sig file temporarily reinstated...


Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"To trace that life in its manifold changes through past ages to the present
is a ... difficult task, but one from which modern science does not shrink.
In this wide field, every earnest effort will meet with some degree of
success; every year will add new and important facts; and every generation
will bring to light some law, in accordance with which ancient life has been
changed into life as we see it around us to-day."
        --O.C. Marsh, Vice Presidential Address, AAAS, August 30, 1877