Archaeopterygid bird from China

[Karl Magnacca]

On 31 Mar 2005 at 8:10, John Grehan wrote:
> I see two problems with this. The first
> is that the assumption of a geographically restricted center of origin
> is just that - an assumption derived from a theoretical postulate that
> begins with Darwin.

birds = almost the whole world
archaeopterygids = China, with one in Europe

That sounds like a geographically restricted center of origin to me.
Yes we could find archaeopterygids in Africa or South America tomorrow,
but no one's holding their breath.

This is the problem with your whole argument: it's against blind
adherence to theory, and Darwin's original faulty logic, not against
this case.

> And Darwin's justification for this theory was not an empirical
> proposition, but a demand for adherence to his personal authority to
> judge the matter as being one of simplicity that leaves any
> alternative view as an appeal to a miracle. Since then most
> biogeographers have followed suit (naturally as most biogeographers
> are Darwinian evolutionists).

I don't think this is true.  It seems to me that most biogeographers
since the 1970's have stuck tightly to vicariance as the main mode of
evolution.  Dispersal is out of fashion.  Get with the program, man!

> > No, it is evidence because the definition of the origin of a group is
> > where the basal member(s) lived.
>
> That seems to be what I said. If one creates a center of origin and then
> define it as the place where the basal member lived then that is what
> one has - whether or not such a center of origin ever existed.

Nobody "created" a center of origin out of thin air.  It wasn't just
decided by committee that China should be the center of origin for
archaeopterygids, therefore any other records are spurious.  It was
based on - I know this is going to be a shocker - empirical evidence,
i.e. the distribution of fossils.

> If an ancestor differentiates vicariously one of the descendant taxa
> will be 'basal' relative to others even though its origin was
> concurrent with all the more derived taxa so the location of the basal
> taxon is no more the 'center' of origin of the group than any of the
> more derived relatives.

If this happens, then you will find all of them distributed across the
entire area from the start.  If, somehow, the first archaeopterygid
lived all the way across Eurasia, you would expect to find them in the
entire area at the same time.  Thus the entire region is the center of
origin.

> You have basically argued the opposite, that the evidence for a
> restricted origin is not empirical since the 'empirical evidence' is
> derived from non-empirical theorizing that a restricted center of origin
> exists in the first place - and that's where I think there is more
> fantasy than reality.

I just don't understand how you reach this conclusion (at least about my
arguments).  Finding a diverse array of fossils in one area, and few to
none elsewhere (and those being later), seems to me to be empirical
evidence that the group originated in that area and had its first round
of diversification there.  There's no theory involved; whatever Darwin
would think is irrelevant.  No it's not conclusive proof, but you're
never going to get that (especially with fossils).  It's a matter of the
evidence at hand.

Karl
=====================
Karl Magnacca, USGS-BRD
PO Box 11, Hawaii Natl. Park, HI 96718
"Democracy used to be a good thing, but now it has
gotten into the wrong hands."   --Sen. Jesse Helms