Re: transitional fossils

Alexanian, Moorad wrote:

> Let us not deny the flexibility, if not total elasticity, that exists
> in the theory of evolution that can account for any new evidence that
> was originally thought as “surprising.” Witness punctuated equilibrium
> which is a modified form of the original thought.
>

Seems that people miss the point. Evolutionary theory either
incorporates the new data or fails to do so. Punctuated Equilibrium is
often seen as a problem for evolutionary theory when in fact it is
providing an explanation for the data based on existing mechanisms of
evolution and speciation.
PE, rather than a modified form of the original thought, basically
extended Darwin's own views on this matter.

> Evolutionary theory is at best pure phenomenology since the “theory”
> is easily modified as new data emerge. It is quite analogous to the
> epicycle theories of planetary motions which can always be arranged to
> agree with data but would have never led to the geocentric theory of
> Copernicus.
>
I have seen quite a few references to epicycles by creationists when
referring to evolutionary theory. There are various problems with this.
First of all, ID and creationism is far more comparable to epicycles
than evolutionary theory because it at most can present ad hoc
rationalizations to explain data.
Evolutionary theory, rather than being 'modified', takes new data and
incorporate it by understanding or speculating about mechanisms and
pathways. In other words, the theory is not 'salvaged' by adding ad hoc
explanations upon explanations but by incorporating new understandings.
A good example would be horizontal versus vertical inheritance. In
Darwin's time, inheritance itself was poorly understood, let alone the
distinction between vertical and horizontal inheritance. Evolutionary
theory however noticed that existing mechanisms of horizontal
inheritance could help understand phylogenies better. It is estimated
that a small percentage of variation is due to such horizontal
inheritance. While initially the hypothesis of horizontal inheritance
may have been seen as an ad hoc explanation, we now know that the
mechanisms exist and have found much supporting data. Evolutionary
theory has succesfully incorporated these findings without having to
abandon the overal theory. Epicycles add as many exceptions as there are
datapoints, evolutionary theory reconciles many datapoints with a single
addition. That's a major difference.

> If evolutionary theory claims that life, consciousness and self are
> all emergent from the purely physical, then is seems to me that
> evolutionary theory can be falsified only if the Creator Himself shows
> up and tells us that it is all pure nonsense.
>
Interesting strawman.

> A theory ought to give rise to logical implications, viz. if A, then
> B. The latter means that ~B implies ~A. It is in this sense that
> falsifiability makes sense. How can evolutionary theory be falsified?
>
>

Good questions and long since answered by Douglas Theobald
http://www.talkorigins.org/faqs/comdesc/phylo.html
29+ Evidences for Macroevolution
Phylogenetics Primer

Douglas presents many potential falsifiers for evolutionary as a fact
and theory and common descent. That evolution has withstood time is
merely an indication of how powerful an explanation it really is. Such
is science, the more solid the theory, the harder it will be to disprove
it, however this does not mean that it is impossible to at least in
principle falsify evolution.

So I find the objections raised by Cornelius and Alexanian mostly
unconvincing as they fail to understand and appreciate what evolutionary
theory is all about.

An example: Evolvability, the ability for evolution itself to evolve was
long seen as a problem for evolutionary theory. How can evolution
explain the origin of variation. Now we realize that evolution has in
fact guided its own variation. A good example is neutrality. Initially
it may sound self contradicting that neutrality can be selected for,
after all it's neutral so why should it be under control of selection.
The answer is simple, and science for long has focused on the wrong
questions: it's not the existing variation but the potential for
variation (also known as variability ((the degree to which new shapes
can be generated by mutating that sequence))) which should be considered:

As Fontana puts it

"The genotype-phenotype map (that is, development) induces the
topological structure of phenotype space by determining the evolutionary
routes along which phenotype B can be obtained from phenotype A. This is
quite different from the traditional image of phenotype space as a
highly regular metric space constructed around a notion of similarity
(morphological or other) between phenotypes. Punctuated equilibria,
constraints to variation and irreversibility in evolution become
intelligible in this new space, its unfamiliar structure notwithstanding."

In other words, understanding the role of tthe genotype-phenotype
mapping has helped understanding various concepts in evolution and
combined them under a single concept. Rather than epicycles,
evolutionary theory actually explains by reconciling 'epicycles' under a
common explanation.

Fontana has written much on this topic http://www.santafe.edu/~walter/

Hope this helps clarify some of these issues.
Received on Sun Dec 4 16:45:48 2005