Re: Therefore, both models are correct.

[Tompaleo@aol.com]

In a message dated 96-01-24 03:29:02 EST, you write:

>Well Rob-again that raised the old unanswered problem-from which the famed
>commercial got it's hit slogan "Where's the beef"..."where's the fossil,
>where's the fossil."
>Grad. is plaqued by that problem and punk just seeks to avoid it.  What's
>wrong with "Abrupt appearences."  I mean the record just says that. No more,
>no less.

But just because the fossil record "shows" a sudden appearance (or
disappearance for that matter) does not necessarily prove that the event was
sudden. There are numeorous factors that continually bias the fossil record.
Many are geologically related such as post depositional diagenesis of the
sediment which may destroy the fossil such as metamorphism, volcanism,
depositional hiatuses and taphonomic biases just to name a few. Then there's
the problem of a particular animal being fossilized at all! Then there is
sampling bias both man made and that caused by weathering/erosion.  So in
essence, the record does not necessarily speak for itself! It would be better
to say (IMHO) that both models are partially right. You have a particular
biota, in the absence of a major calamity,  species evolve and go extinct at
a "regular rate". According to Bakker and others this rate is about 2 Million
years on the average per species. This is the "background" extinction. Then
periodically(?), a calamity strikes that affect large numbers of taxa and
then you have a mass extinction.  The survivors then move in to the niches
left vacant by the mass extinction and soon begin a new period of
origination.  The above factors that affect fossilization /preservation
/recovery  tend to bias our opinion in the direction of "sudden appearance"
 events that were obviously gradual.  To me, that is what the geologic
recrord is telling us. INMHO

Regards,
Thomas R. Lipka
Paleontological/Geological Studies