Re: transitional fossils

From: Keith Miller <kbmill@ksu.edu>
Date: Sat Dec 03 2005 - 18:39:08 EST

> PE's call for non uniform morphological change was in response to the
> non uniform character of the fossil record. It is not based on
> population genetics. If you do not presuppose evolution to begin with,
> then population genetics does not particularly help. That is,
> population genetics does not, itself, indicate PE.

Gould and Eldredge's proposal was based on applying the consequences of
the allopatric speciation model to the fossil record. They argued that
the common pattern of species evolution in the fossil record was
consistent with the expectation of the allopatric model and lineage
splitting (cladogensis). Again the object of the PE model was
speciation.

> The term "Transitional forms" is not a theory-neutral description of
> the data. Those forms are "transitional" if evolution is true. The
> bottom line is that the fossil record is characterized by the rapid
> appearance and then stasis of new species. Species persist for eons
> with little or no change. You can try to align those species in
> "transitional" sequences if you like. What you will find is a wide
> variety of patterns, all of which evolution can explain by one means
> or another (gradualism, PE, missing data, selection, no selection,
> environmental shifts, saltation, co-evolution, and so forth). All of
> these explanations are used today, but we still are left with rapid
> appearance and then stasis of new species. Hence PE. It provides an
> explanation for those dashed lines between the "transitional" species.

The formation of new species is well-documented in the fossil record
and observed today both in the field and under experimental conditions.
  Species formation is not something hypothetical. The fossil record of
speciation includes examples of gradual change as well as more
punctuated patterns. The debate is over which of these patterns are
more typical and what genetic and environmental factors are at play.

At higher taxonomic levels, transitional forms are known for many
groups such that the definitions of these taxonomic groups break down
and the fossil specimens cannot be easily classified.

Note: If someone chooses to reject evolution a priori, then absolutely
no fossil evidence regardless of how complete will be statisfactory for
them.

Another critical point is that many of the fossil transitions now known
were predicted on the basis of evolutionary models. That is, the
fossils were discovered after their existence was predicted. It is
this predictive ability which makes evolutionary theory a powerful
model for the history of life.

Keith B. Miller
Research Assistant Professor
Dept of Geology, Kansas State University
Manhattan, KS 66506-3201
785-532-2250
http://www-personal.ksu.edu/~kbmill/
Received on Sat Dec 3 18:45:05 2005

This archive was generated by hypermail 2.1.8 : Sat Dec 03 2005 - 18:45:05 EST