Archaeopterygid bird from China

[Barry Roth]

--- Karl Magnacca <kmagnacca at WESLEYAN.EDU> wrote:
[...]
> 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.

In order to be a hypothesis, which is what everyone seems to want, a
proposition must be testable.  What kind of evidence can test (and potentially
falsify) the proposition that a certain fossil at a certain geologic time and
geographic place documents, roughly, the time and place of the origin of its
clade?  Not more fossils, if, as per John Grehan, the chrono-geographic
occurrence of fossils is irrelevant to detecting origins.  I suppose if there
were many fossils of a taxon, all at about the same age horizon, and widely
spread geographically, most observers would balk at declaring one or the other
to definitely represent _the_ place of origin of the taxon.  Either they all
are (per the school of Grehan) or one is (but we don't know which one) and the
taxon spread quickly over a large area soon after its origination: so rapidly
that stratigraphic resolution is not precise enough to sort it out.  How about
the evidence of phylogenetic analysis combined with the distribution of related
taxa -- i.e., phylogeography?

Barry



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