Biogeography and geological prediction

john Grehan jgrehan at SCIENCEBUFF.ORG
Thu Feb 6 08:56:37 CST 2003

Peter wrote:

>So here my interpretation seems to have been correct: biogeographic
>analysis is not to be informed by the results of geological analysis.

Correct - at least for panbiogeography. Panbiogeography is an research
program with its own principles and methods.

>To talk about a "spreading ridges", "former coastlines" and at the same
>time to deny the historical elements contained in these terms strikes me
>as odd.
>It never occurred to me before that Pan might be an approach directed at
>avoiding all historical interpretations of our current observations - yet
>this seems to be what John Grehan is driving at.

The whole point of correlations between biogeographic patterns and these
features is their historical significance. However, the geohistorical
narratives associated with such features are not the basis for
panbiogeographic analysis. Panbiogeographic reconstructions may, however,
be discussed in relation to those geohistorical narratives associated with
the geomorphological features identified in the spatial correlation. Thus,
the baseline for Galapagos tracks gives reason for discussion of the
geological narratives for the East Pacific.

>Not informing a "method", but surely here a biogeographic pattern is
>presented as informing an geological hypothesis about the history of these

Informing in the sense of recognizing a compatibility between a
geohistorical hypothesis and a biogeographic pattern. I would see the
converse, a geological pattern (not a geohistorical narrative) informing a
panbiogeographic hypothesis.

>It does not have to influence the method - but all I ask is why it is so
>vehemently denied that this historical context can ever be used to inform
>the results of the biogeographic analysis in the same way that it is used
>to help decide between alternative explanations of the geological

Historical context in the form of geohistorical narratives are simply
theories or conjectures that may or may not be wrong. To base biogeographic
speculation upon geological speculation is something that some may accept
and some may not.

>Perhaps, but I see this as evasive. If we do science, we should,
>occasionally, ponder the possibilities to justify the methods we are using.
>Appeals to personal taste are poor justifications.

This is a presumption that choices are based on universal criteria. History
seems to say otherwise. My statement is a recognition that people -
scientists included - have personal preferences. Thus, one may not like
panbiogeography no matter what purely 'scientific' justification is brought
forward. Cladistics did not eliminate personal preferences for phenetics
for example.

Peter's second email points to the issue of personal choice. On the fact
that panbiogeography has made successful geological novel predictions
(whereas Darwinian biogeography has not) Peter stated:

Croizat wrote quite lot - there may even be some unsuccessful predictions
hidden away in the 5K pages comprising his books. And the prediction of a
"major tectonic feature" involved in an oceanic island group strikes me as
rather unspecific - and one that would hold for quite a large number of
island groups (or else there wouldn't be any islands on that location).
Maybe it is possible for someone with plenty of time, and all of Croizat's
writings at hand, to compile a simple list of all his predictions, and to
score those predictions as either successful or not. Only with a list like
that will it be possible to assess the actual success of Croizat's method.
Failing such a list, I think one would be justified in regarding this much
flaunted successful prediction simply as a fluke.

Here is an acceptance of the reality of panbiogeographic success (something
that many Darwinian biogeographers and critics have avoided or dismissed).
Does that lead Hovenkamp to apply and develop the panbiogeographic method
and synthesis? Peter takes the alternative of suggesting the successes were
generalized and possibly flukes anyway. This is according to personal
choice. For me, I take an interest in the biogeographic method that has
generated novel geological predictions (such as the composite tectonic
structure of the Americas) later corroborated by another discipline
(geology) over an alterative that has not (e.g. the Darwinian approach)
whether or not the success is relegated by philosophers to being a 'fluke' etc.


Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, New York 14211-1293
Voice 716-896-5200 x372
Fax 716-897-6723
jgrehan at

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