Archaeopterygid bird from China

[Richard Jensen]

John Grehan wrote:

> Dick said:
>
> I see nothing unscientific about hypothesizing that the
> > area of origin is near the older rather than the younger fossils.  It
> is, after
> > all, only a hypothesis.  We have to start somewhere and this provides
> a
> > starting point.
>
> My question is why start with this premise in the first place? What is
> the empirical evidence that there is any necessary relationship between
> the location of the oldest fossil and a theorized restricted center of
> origin?

As I said, we have to start somewhere.  We could just as easily start with
the hypothesis that this is not the "center" of origin.  Either of these
hypotheses is better than just letting the observation sit in an
intellectual vacuum.

>
>
> >
> > Is it an empirical observation?  No; it's a hypothesis based on the
> > information at hand.
>
> I would argue that the hypothesis is not based on the information at
> hand. The information at hand is simply that the location of the oldest
> fossil is the location of the oldest fossil.

Of course it's based on the information at hand - it's the only information
we have.

>
>
> There are two possibilities: the taxon had its
> > origin
> > in eastern Asia or it did not.
>
> There is another possibility, that the taxon had its origin
> simultaneously in eastern Asia and Europe.

Oh, you believe in something akin to the multiple origins hypothesis of
Homo sapiens?  Populations in eastern Asia and western Europe independently
evolved into a single clade?  My bet is that the family (the clade in
question) had a single place of origin and that, if it is a monphyletic
"group", multiple origins did not occur.

>
>
> I am free to choose either as my working
> > hypothesis - I can invoke parsimony to justify my hypothesis that the
> > oldest
> > fossils are near the area of origin;
>
> It might be parsimonious if one starts with the premise that there is a
> necessary relationship between a fantasized center of origin and the
> oldest fossil.

No fantasized - hypothesized.  The location of the oldest known fossil is
our best estimate of the place of origin.  As I said before, it's not
necessarily the real place of origin, but we have no evidence to the
contrary.

Dick J.

--
Richard J. Jensen              | tel: 574-284-4674
Department of Biology      | fax: 574-284-4716
Saint Mary's College         | e-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen