Paleontology and molecular clocks

From
Date
To try and pursue a positive thread in discussing new directions and
broader "relevance" of paleontology, our discipline can have a major role
in supporting molecular systematics.  "Molecular clock" studies of
phylogeny often seek reliable dates for time of origin of one or more
included clades.  Many "biological" paleontologists will know about this
contribution of paleontology, but stratigraphic paleontologists might not
have latched onto it fully.  (Excuse me if this is familiar ground.)  For
the record, examples of recently published papers that emphasise fossil
calibrations include:

        Arnason, U. et al.  1996.  Pattern and timing of evolutionary
divergences among hominoids based on analyses of complete mtDNAs.  J MOL
EVOL 43: (6) 650-661   [Includes calibrations from fossil whales.]

        Cooper, A., and Penny, D.  1997.  Mass survival of birds across the
K-T boundary.  Science 275 (5303): 1109-1113.  [Uses multiple calibrations
from fossil birds.]

But, the fossil record is not always accorded as much weight as we might
hope; see e.g.

        Milinkovitch, M. C.  1995.  Molecular phylogeny of cetaceans
prompts revision of morphological transformations.  Trends in ecology and
evolution 10 (8): 328-334.  [Here molecular conclusions are quite at odds
with stratigraphy and anatomical cladistics.  Alas, the molecular results
have been accepted by many as "gospel" . . . the opposing anatomical
studies are just too hard to work through, I suppose.]

Here's a chance to work in collaborative fashion outside our normal circles
. . .

R. Ewan Fordyce
Associate Professor, Department of Geology
University of Otago, PO Box 56, Dunedin, NZ