Hi George, thank you for your comments!
george murphy wrote:
>
> pruest@pop.dplanet.ch wrote:
>
> > Jonathan Wells' "Icons of Evolution" has been criticized repeatedly and
> > recommended a few times on this list. J.A. Coyne's rabid criticism,
> > "Creationism by stealth", Nature 410 (12 April 2001), 745-746, has also
> > been mentioned.
> >
> > In Reasons to Believe's Facts for Faith issue 5 (1/2001), pp. 60-61,
> > Fazale R. Rana provides a very much more sympathetic discussion of
> > "Icons".
>
> There is no single set of observations &/or experiments which _prove_
> biological evolution in general or a particular theory of biological
> evolution. That's the case with any scientific theory & is especially so
> with one like evolution in which a great deal of the relevant phenomena were
> in the past. In addition, any number of theories can be developed to
> explain a given observation. _Ceteris paribus_, the best theory is the one
> which explains the widest range of observations with the fewest number of
> _ad hoc_ &/or untestable hypotheses. A number of the following criticismss
> are effective only to the extent that the experiments or observations are
> supposed to be "proofs" of evolution rather than evidence which is
> supportive of it. In particular ...
I agree with your basic concept of a scientific theory and it's (lack
of) general provability. I don't expect textbooks to give "proofs" for
evolution, and I consider neither Wells' nor my objections to be
"proofs" against evolution. However, we should expect textbooks
presenting evidence for evolution to select the strongest pieces of
evidence available. If all of what they provide is either irrelevant, or
ambiguous as evidence, they aren't doing a good job. The crucial point
is that evolution usually is presented as an undisputable fact, and not
just as the theory "which explains the widest range of observations with
the fewest number of _ad hoc_ &/or untestable hypotheses". In fact, the
principal untestable hypothesis assumed is philosophical naturalism. The
power of the evidences for evolution depends very much on the previous
assumption of theism or atheism. Therefore, the value of a given piece
of evidence will be judged very differently by different scientists of a
similar competence in the relevant fields of study. What is singularly
lacking today in the usual views of the origin of life and biological
evolution is a critical attitude regarding interpretations of the data.
> .....................................
>
> > 1) The Miller-Urey experiment: those in origin-of-life research agree
> > that Miller's reaction conditions were much too reducing to
> > realistically simulate conditions on the primitive Earth, and the few
> > resulting amino acids are a very far cry from what is needed for even
> > the first steps of generating life.
>
> Of course the results of the MU experiment are far from solving the
> problem of chemical evolution. But the final clause is a considerable
> overstatement. The experiment showed that, under what were then considered
> to be plausible conditions, amino acids - which can certainly be called
> "first steps" in chemical evolution - could be produced. & this inspired a
> lot of other experiments which still haven't solved the problem but which
> are not all subject to the same criticism as the original & relatively
> primitive MU work.
Even including all experiments done since the first by MU, I don't think
I have to change my final clause. Consider a recent conclusion by L.E.
Orgel, one of the leading researchers in the field (Trends Bioch. Sci.
23 (Dec. 1998), 491):
"There are three main contending theories of the prebiotic origin of
biomonomers [1. strongly reducing primitive atmosphere, 2. meteorites,
3. deep-sea vents]. No theory is compelling, and none can be rejected
out of hand...
"The situation with regard to the evolution of a self-replicating system
is less satisfactory; there are at least as many suspects, but there are
virtually no experimental data...
"[There is] a very large gap between the complexity of molecules that
are readily synthesized in simulations of the chemistry of the early
earth and the molecules that are known to form potentially replicating
informational structures...
"Several alternative scenarios might account for the self-organization
of a self-replicating entity from prebiotic organic material, but all of
those that are well formulated are based on hypothetical chemical
syntheses that are problematic...
"I have neglected important aspects of prebiotic chemistry (e.g. the
origin of chirality, the organic chemistry of solar bodies other than
the earth, and the formation of membranes)...
"There is no basis in known chemistry for the belief that long sequences
of reactions can organize spontaneously - and every reason to believe
that they cannot."
> > ..............................................
> >
> > 3) The homology of vertebrate limbs: the main problem with all
> > similarities between functional features is that they may need to be
> > similar in order to function: thus, they cannot be evidence for common
> > descent. Genuine evidence for homology may require functionless features
> > (cf. my "How has life and its diversity been produced", PSCF 44
> > (2/1992), 80-94).
>
> I.e., homology doesn't support evolution because limbs MAY (Sic!)
> need to be similar in order to function? Unless it can be shown that the
> limbs actually DO need to be similar to function, this argument is vacuous.
> But even if that could be shown (which I think is unlikely), it doesn't
> explain _how_ the limbs of diverse species came to be homologous. Waiting
> to jump out here is perhaps the answer, "God made them that way." But while
> I agree that "God made them", that isn't a scientific theory.
As Tim Ikeda indicated (28 May 2001 09:49:18 -0400), macroscopic systems
such as limbs consist of multiple components, each with its function. In
individual components, e.g., "there are examples of enzyme active sites
where strong arguments can be made for convergence rather than
homology". For the extension of this ambiguity to composite systems see
my answer (30 May) to Tim regarding similarities between cladistic
trees. Saying that functional features "may" need to be similar in order
to function, I primarily considered individual molecular features and
meant that we should expect them to be similar, quite apart from a
possible common descent. In view of the many known cases of molecular
convergence, the argument is not at all vacuous. Each case of
convergence produces an erroneous discrepancy between the cladistic tree
of the feature considered and the (unknown) true phylogenetic tree. The
analysis of the huge database of the human genome demonstrates how
difficult it is to be sure of a homology on the molecular level (W.H.
Li, Z. Gu, H. Wang, A. Nekrutenko, Nature 409 (15 Feb 2001), 847), not
to speak of the much more intricate problem of homology on the
macroscopic level. I certainly would not use the
"God-made-them-that-way" answer, but the textbook "demonstration" of
homology by means of the vertebrate limbs is all too simple-minded.
> Shalom,
>
> George
>
> George L. Murphy
> http://web.raex.com/~gmurphy/
> "The Science-Theology Dialogue"
Peter
-- -------------------------------------------------------------- Dr Peter Ruest Biochemistry Wagerten Creation and evolution CH-3148 Lanzenhaeusern Tel.: ++41 31 731 1055 Switzerland E-mail: <pruest@dplanet.ch - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - In biology - there's no free lunch - and no information without an adequate source. In Christ - there is free and limitless grace - for those of a contrite heart. --------------------------------------------------------------
This archive was generated by hypermail 2b29 : Thu May 31 2001 - 11:06:11 EDT