Chris Cogan wrote:
[...]
CC>Evolution is *definitely* not to be regarded as always
CC>proceeding at a constant rate (by any measure that I can think
CC>of). This "uniformitarianism" was one of Darwin's biggest
CC>mistakes.
[...]
Except that Darwin did not espouse a "constant rate" view of
natural selection. At least, I haven't seen any prose from
Darwin that sets aside his identification of intermittent
action of natural selection.
I think, Chris, that you grant Johnson too much credit in his
assertion that the invertebrate fossil record fails to clearly
document transitional sequences. In fact, my reading leads me
to almost the opposite conclusion -- the invertebrate fossil
record yields a richer source of data concerning transitions
than does the vertebrate record. I routinely ask those who
deny that any transitional sequences exist to explain what,
precisely, might disqualify the transition discussed in
the following paper:
Pearson, P.N.; Shackleton, N.J.; and Hall, M.A., 1997.
Stable isotopic evidence for the sympatric divergence of
_Globigerinoides_trilobus_ and _Orbulina_universa_ (planktonic
foraminifera). Journal of the Geological Society, London,
v.154, p.295-302.
Researchers at Florida State Univerity (Arnold and Parker) put
together a large-scale collection of foram data showing
transitions. A longer article used to be available, but
<http://geomag.gly.fsu.edu/research/paleo.html> seems to
describe the department broadly.
Roger Cuffey's article on paleontological evidence printed by
the ASA in 1974 cited many (>100) research papers, and the
majority of those were of invertebrate studies.
[Quote]
Planktonic foraminifera provide a unique tool for assessment
of rates and patterns of morphological evolution. It is in
this group of fossils where the best documented examples of
evolutionary transitions between species have been
described. Yet, although the fossil record of planktonic
foraminifera allows direct tracing of ancestry, quantification
of rates of morphological change and tracking of spatial
patterns of speciation, the insufficient knowledge of the
function of their shells has been gravely limiting the
interpretation of such data. Recent advances in DNA extraction
from modern planktonic foraminifera, as well as stable
isotopic studies of habitat changes of their fossil relatives
have cast additional doubts on the biological meaning of the
well documented evolutionary patterns in this group. If there
are cryptic species of planktonic foraminifera, if changes in
the shape of their shells during the evolution occur out of
phase with changes in their ecological preferences, does it
mean that shell form is in fact not subjected to the machinery
of natural selection?
Here, I present data on morphological evolution in a late
Neogene planktonic foraminifer lineage. A detailed
investigation of the changes in the relative abundance and
size of secondary openings in the shells of this lineage
suggests that there was a strong selection against this
character. Thus, it seems that at least in some cases
morphological evolution of planktonic foraminifera may indeed
reflect the biological processes of natural selection. This
implies that recent findings on the functional morphology of
planktonic foraminiferal shells do not imply a threat to
studies of morphological evolution in this group; rather they
provide a challenge and a great prospect for future
investigations.
[End Quote -
<http://www.campublic.co.uk/science/publications/JConfAbs/4/278.html>]
Five out of six examples at
<http://www.cs.colorado.edu/~lindsay/creation/fossil_series.html>
concern invertebrates.
Discussion of speciation in the fossil record in
<http://mercy.georgian.edu/~wootton/FOSSWEB.html> discusses
four groups of invertebrates.
Wesley
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