dispersal fantasy

[pierre deleporte]

At 11:19 25/06/2002 -0400, John Grehan wrote:
>Pierre Delporte wrote:
>(...)
>  Relying on possibly strong geological evidence for
>explanation is in fact a way for such an integration (between biology and
>geology).
>  Let's rather discuss the arguments.
>
>JG: It is not integration in the sense that there is no independent
>historical contribution from biology. Everything is interpreted in the
>light of current 'knowledge' (I current understanding of historical events).

There is independent contribution from biology: the genetic datations and
phylogenies, confronted with the geological scenario, and allowing to check
for inconsistencies under some interpretative assumptions ("model"). Also,
everything is always interpreted in the light of current knowledge. Cannot
be otherwise.

>J.G.: here I was critiquing the method of constructing a narrative based
>on another narrative.

Well-argued "narratives", i.e. historical inferences, may effectively at
some moment be considered as belonging to background knowledge for further
explanation. If the narrative is revised, then background knowledge is
modified and the scientific explanation may change. No methodological
problem, I think.

>If there is no biogeographic analysis generating historical predictions
>then it seems that biogeography of itself has no status as a science.

I seems that we are touching a good point for discussion here. It happens
that such a "predictive" or "refutationist" way of viewing historical
reconstruction has parallels in other fields.

So you require that historical inferences, reconstructions of the past,
proceed from, or participate in, generating predictions ? Unless they would
not belong to science ?
And so, retrodiction (historical biogeography) must generate prediction ?
Or be thrown away from science ?

In my view, retrodiction is historical explanation, a mere case of
inference to the best explanation, based on current (=background)
scientific "knowledge". Relevant data and logics for reconstructing the
past are necessarily theory-loaded. Scientific explanation differs from
trivial explanation in that it relies on *scientific* theories and
"knowledge". We (alaways provisionally, in science) put in background
knowledge what is considered sufficiently supported, and use this as
reference for explanation. An accepted "narrative" (a geological
evolutionary scenario for instance) may belong to background knowledge
(e.g. approximate age of the earth, or of formation of a geological
feature).  Now, we can put things another way: rely on a biological
scenario or law (of evolutionary process of speciation and spatial
distribution) in order to infer geological historical explanation. Or
combine arguments some way. Yes we can, we just have to argue what is
relatively strong evidence, and what is relatively doubtful evidence, at
some moment of the development of science.

But the exigence of predictivity for a retrodictive approach seems to me
basically ill-conceived and highly confusing.

>It becomes fantasy here in the way that it is built up on a narrative
>foundation, not an analytical methodology to generate predictions about
>such processes.

What about trying yourself to make a prediction ? Not the "prediction" that
your present scenario or that of a colleague is right and will resist to
further development of science, or to the gathering of more data, or to the
progress of methods; or, to the contrary, will be discarded in the future:
this would be quite trivial and without any scientific interest (maybe only
for the "little history of science"). I mean a prediction from a predictive
theory. Just try it, and it will be possible to assess the support and
productivity of such a "predictive approach" in historical (= retrodictive)
biogeography.

Just a hint anyway: evolutionary predictions require general theories about
the evolutionary process for "some features in some contexts", they cannot
come from historical approaches in themselves. They must come from elsewhere.
I have no "historical biogeography predictions". Not a matter of taste, but
logics, IMHO.

Best,
Pierre