Re: transitional fossils

Cornelius Hunter wrote:

>
>
>>> 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 allopatric speciation model was developed by Ernst Mayr, an
> evolutionist. It is a qualitative model that he used to explain the
> data assuming evolution is true. It does not come out of population
> genetics, per se. Even Mayr admitted that no model explains the
> details of speciation (involving anything more than minor
> morphological change which for some would not even qualify as
> speciation):
>
> "In particular, there is one problem that is not yet entirely solved.
> When we look at what happens to the genotype during evolutionary
> change, particularly relating to such extreme phenomena as highly
> rapid evolution and complete stasis, we must admit that we do not
> fully understand them. The reason for this is that evolution is not a
> matter of changes of single genes; evolution consists of the change of
> entire genotypes." [What Evolution Is, p. 272]
>
> Indeed. Population genetics does not indicate that adaptative changes
> should give the massive change required for evolution.
>
Hence the combination of population genetics with developmental
evolution which helps explain the observations. And while evolution does
not 'require' massive change, evo-devo is unravelling how novel and
complex pathways have arisen. That evolution does not fully understand
all the aspects should of course not be seen as a problem unique to
evolution.

>
>> 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.
>
>
> What is important to understand about these examples from the field
> and fossil record is that they involve minor morphological variations.
> The genotype (and phenotype) has not undergone anything qualitatively
> like what evolution needs. Even evolutionists doubt that these changes
> and their mechanisms are sufficient to account for the larger changes
> evolution requires.

Again this is contradicted by the data. In fact the genotype and
phenotype need to be separately treated due to the neutral pathways in
the genotype which can create much variation. Again, the combination of
genetic changes and their impact on the phenotype is a fascinating topic
and recent work is slowly unraveling even the most abrupt of all
changes, the Cambrian. Foremost researchers in this area have realized
that the Cambrian, which appeared to some to be an enigma for
evolutionary theory, is hardly that enigmatic anymore.

>
>
>
>> 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.
>
>
> Everybody slips up now and then, but ad hominems like this don't help.
>
How is this anymore ad hominem than claiming that Mayr based his ideas
on the assumption that evolution were true? The 'only' difference is
that evolutionary theory does explain the data in a beautiful manner and
that competing explanations, especially relevant to the concept of ID
are fully lacking.

>
>> 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.
>
>
> Yes, that is true. However, there are so many other predictions of
> evolution that have been falsified that it is not clear how much value
> there is in pointing to those predictions that were successful.
> Geocentrism has many successful predictions to its credit as well.

Ah yes, these mythical falsifications of evolutionary predictions...
Funny how evolution has withstood the attempts to falsify it and is
blossoming in the new era of genetic and developmental research. Oh yes,
many surprises have arisen over time and evolution has succesfully
adapted to them.

 From the evolution of the genetic code to the developmental pathways
evolutionary theory is exploring fascinating worlds.Remind me again what
ID's contribution in these areas has been?

examples include

This represents another successful evolutionary prediction. What we
expect to find in biology is that the networks of genes responsible for
specific morphological features in complex organisms will also be
present in simpler forms, but with broader, more general, and sometimes
rather different functions. With /Trichoplax/, we're identifying the
evolutionary foundations of some of the most basic features of our
embryonic organization—features so primitive that we take them entirely
for granted.

http://pharyngula.org/index/weblog/comments/mysterious_trichoplax/

/Science/ has published a description of a new specimen of
/Archaeopteryx/, the best preserved one yet, with clearer preservation
of the skull and feet. What it reveals are details of the limbs:
/Archaeopteryx/ lacked the opposed first toe of modern birds, so it
lacked the ability to perch, but it did have an extensible second toe,
rather like the terrible claw of /Deinonychus/. The discovery tightens
the affinities between birds and theropod dinosaurs.

http://pharyngula.org/index/weblog/comments/new_archaeopteryx_specimen/

Now here's a paper on the comparative analysis of introns with a pair of
surprises. Surprise #1: the introns in our genes are highly conserved,
and about two thirds of the human introns examined were also present in
our urbilaterian ancestors at the very same amino acid position and
phase. What that means is that this peculiar disruption of our genes
occurred in multicellular animals /before/ the Cambrian, and we have
preserved this quirk for half a billion years. While sequences have
diverged, the way the genes are organized in blocks has been conserved.

Surprise #2 (although it shouldn't be): we vertebrates are /primitive/.
Other clades have modified their gene structure over evolutionary
history more than we have, and our genes are more similar to those of
some obscure marine worms than they are to those of insects, for
instance, and have changed less than those of some of our closer relatives.

http://pharyngula.org/index/science/comments/we_are_as_worms/

So fish have gills to regulate calcium, and we have parathyroid/thyroid
glands to regulate calcium. Do they have anything else in common? One
minor thing seems to be location: gills are in the fish's 'neck', and
the parathyroid glands are located at roughly the same place, in your
neck—and that's interestingly coincidental, since there's no particular
/need/ for these glands to be in that particular location. They can do
their job just as well anywhere. And they happen to be located in a
particularly fascinating place for those of us curious about vertebrate
evo-devo; all kinds of action occurs in this pharyngeal region in early
development.

http://pharyngula.org/index/weblog/comments/deep_homologies_in_the_pharyngeal_arches/

      Which Came First, the Snake or the Venom?

<http://www.corante.com/loom/archives/038391print.html>

Posted by Carl Zimmer

Back in February I discovered the remarkable work of Australian
biologist Bryan Grieg Fry <http://venomdoc.com/>, who has been tracing
the evolution of venom. As I wrote
<http://carlzimmer.com/articles/2005/articles_2005_venom.html> in the
/New York Times/, he searched the genomes of snakes for venom genes. He
discovered that even non-venomous snakes produce venom. By drawing an
evolutionary tree of the venom genes, Fry showed
<http://www.corante.com/loom/archives/2005/04/04/doctor_venom.php> that
the common ancestor of living snakes had several kinds of venom, which
had evolved through accidental "borrowing" of proteins produced in other
parts of the body. Later, these genes duplicated to create a
sophisticated cocktail of venoms--a cocktail that varied from one
lineage of snakes to another.

As I report <http://www.nytimes.com/2005/11/22/science/22venom.html>
tomorrow in the /Times/, Fry has taken this research the next logical
step. He set out to find out when that ancestral venom evolve. In his
search, Fry made an astonishing discovery: snakes are 100 million years
old, but snake venom is 200 million years old. This conclusion arose
from the fact that some lizards produce the same sorts of venom as
snakes--including this desert spotted monitor that Fry is posing next to
on one of his venom expeditions in the Outback.

http://www.corante.com/loom/archives/2005/11/21/which_came_first_the_snake_or_the_venom.php

Previously, it was thought that venom production in snakes and lizards
had evolved independently, since the venom glands in these lineages had
a different structure. However, using new DNA sequence data, Dr Fry and
his colleagues found nine venom toxin types that were shared between
lizards and snakes. Seven of these were previously only known from snake
venoms, including one that had only previously been reported in
rattlesnake venom but was sequenced by the team from the Bearded Dragon.
Looks like yet another paradigm-shattering paper; y'know, the kind all
the IDists say scientists are so afraid of...

http://aetiology.blogspot.com/2005/11/of-dragons-and-microbes.html
Received on Sun Dec 4 14:09:03 2005