Islands, Science and Creationism

John Grehan jrg13 at PSU.EDU
Mon Apr 15 08:22:28 CDT 2002

Geoff Read wrote:

>  Sure it's interesting to
>speculate  if eroding, sinking Galapagos hotspot volcanic islands carried
>eastwards made it much closer to a large body of 'mainland' in the past than
>they do currently before disappearing beneath the tide, but is there good
>evidence they ever did?  The authors below conclude "... it is unlikely 
>that it
>will ever be possible to reconstruct a continuous history for a Galapagos
>archipelago, which is essential for the survival of Galpagos biota, beyond
>about 15Ma." (because of  75 m.y. of subduction under Costa Rica).

I have no problem with any of the above (although the geological models to 
which I referred to in the Galapagos paper primarily involved mobile island 
arcs, not eastward moving Galapagos islands although this possibility was 
acknowledged in reference to a paper by Hauff et al., 1997). None of the 
above conflicts with the fact that Croizat predicted the existence of a 
major tectonic structure at the Galapagos and that this prediction was 
empirically corroborated through subsequent geological discovery. The other 
fact is that Croizat's historical geological model of mobile geosynclines 
and associated island clusters is conceptually compatible with plate 
tectonic island arc models for the region.

I am in complete agreement with the quote about reconstruction of a 
continuous geological history for a Galapagos archipelago being unlikely. 
This provides a very good illustration of why biogeographic reconstruction 
cannot simply be based on geological speculations (models) about the past. 
This is exactly what Darwinian biogeography did for the Galapagos with all 
its assertions of overwater dispersal being the only possible origin for 
the Galapagos biota. Croizat's approach did not rely on accepted historical 
geological reconstructions and his method took theory ahead of the current 
knowledge of the time and generated predictions of future empirical 
discovery. Regardless of philosophical and rhetorical objections and the 
priority traditionally given to other disciplines over biogeography, 
panbiogeography actually works.

With respect to these various geological views, I submit they further 
illustrate the problematic nature of presenting the science of evolution as 
a doctrine of beliefs. In my own field of biogeography I would emphasize 
the science of evolution as a theoretical framework that allows one to go 
ahead of current empirical knowledge and generate novel predictions of 
future empirical discovery (in the same way that relativity theory 
generated predictions in physics). This approach would show the practical 
real-world power of evolutionary theory where the theoretical models about 
the past are represented as simply summaries of current knowledge generated 
by a methodology that is of itself not constrained by current knowledge 
(poorly worded perhaps but I hope that makes sense).

John Grehan

>* Werner, R., K. Hoernle, P. van den Bogaard, C. Ranero, R. von Huene, &
>D. Korich. 1999. Drowned 14-M.y.-old Galapagos Archipelago off the coast of
>Costa Rica: Implications for tectonic and evolutionary models. — Geology
>   Geoff Read < at>

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