For those unfamiliar with Behe's views and the common criticisms, there
are a fair number of on-line resources. Here is a list of a few of
them.
Behe's own position:
http://www.arn.org/arn/articles/behe924.htm
http://www.atr.org/discovery/behespch.html
An anti-Behe page entitled "Behe's Empty Box":
http://www.spacelab.net/~catalj/box/behe.htm
The talk.orgins critique by Keith Robison:
http://www.talkorigins.org/faqs/behe.html
An exchange in the pages of the Boston Review in response to a review
by H. Allen Orr:
http://www-polisci.mit.edu/BostonReview/BR21.6/orr.html
http://www-polisci.mit.edu/bostonreview/evolution.html
Text of my critique given at the ASA meeting in 1994 in a debate with
Mike Behe: http://mcgraytx.calvin.edu/gray/irred_compl.html
Warning: Personal opinion scattered throughout.
OVERVIEW
My overall reaction to the mini-conference is this: I was pleasantly
surprised at how much the debate stayed on the fundamental science
question, i.e. is there a plausible account for the origin of
"irreducibly complex" systems in a Darwinian framework. Even though
Behe has become an advocate of "intelligent design" and Dennett is an
advocate of accepting the full implications of "Darwin's dangerous
idea", i.e. a full-blown atheism, the presentations and question/answer
periods focused on the basic, technical biochemistry questions. The
rhetoric (on both sides) surrounding whether or not "intelligent
design" is a scientific notion was largely missing.
BEHE
Mike Behe presented the basic thesis of his book. A good summary can be
found at http://www.arn.org/arn/articles/behe924.htm and
http://www.atr.org/discovery/behespch.html.
The structure of the paper was essentially unchanged from his 1994
presentation at the ASA meeting in his debate with me. He puts forward
the argument that living things are irreducibly complex and thus could
not have arisen gradually by Darwinian natural selection. By
irreducibly complex systems Behe refers to systems in which each
component plays an essential role in the functional whole such that
only when all the components are present and functioning correctly does
the functional whole exist. The argument against evolution neatly
flows, almost syllogistically, from this definition. It is impossible
for natural selection to produce such a system in a stepwise fashion
since all the parts must already be present to in order to have a
function to select.
Behe appeals to biochemistry in defense of his thesis. Modern
biochemistry has opened the "black box" of living systems by
elucidating the incredible complex molecular machinery underlying them.
The novelty of his claim, as against other similar arguments against
evolution (and for a designer) such as Paley's, is that now we
understand life at its fundamental molecular level.
My notes are scarce on the Question and Answer period, but two
questions/comments do stand out in my mind. Philosopher of science
Ernan McMullin asked Behe if he thought that God could cause
"irreducibly complex" structures to arise using "natural causes". Behe
paused, as one should when one is asked about something that God might
not be able to do. His answer was revealing, however. He suggested that
God could have ordered the universe so that 40 different cosmic rays
might simultaneously strike some primordial cell causing the
simulataneous mutation of all the right genes that would result in the
formation of a novel irreducibly complex structure. [TG: Why God
couldn't do the same thing in a "less obvious" way strikes me as the
obvious question to follow-up with.]
One person commented that Darwinists expect irreducible complexity. The
idea is that the initial function arises in the context of a more
complex system (but not necessarily irreducible) and that evolution
fine tunes this system and removes extraneous pieces leaving the
absolute minimum structure that looks, indeed is in its present state,
irreducible. Behe's response was simply that if you can't explain the
origin of the less complex system, then it would be more difficult to
explain the origin of the more complex system.
HAIG
David Haig is an evolutionary geneticist/theorist who does research in
the area of imprinting. But he had done his biochemistry research and
focused entirely on a biochemical response to Behe's arguments.
He started quoting from the Behe's response to the Orr review in the
Boston Review
(http://www-polisci.mit.edu/bostonreview/br22.1/behe.html) where Behe
claimed, "Evolutionary biology can't overrule biochemistry on
fundamental principles of life. It's not a question of pride--that's
just the way the world works." and "Since inherited changes are caused
by molecular changes, it is biochemists--not evolutionary
biologists--who will ultimately decide whether Darwin's mechanism of
natural selection can explain life. No offense--that's just the way the
world works." [TG: Of course, in stressing the priority of
biochemistry, Behe only gives his view of biochemistry--he doesn't
mention that there are many biochemists who disagree with him.] Haig
disagreed with Behe in these claims and pointed out that biochemists
(at least those who don't think in evolutionary terms) sometimes view
the genes as "the unmoved mover" and forget that genes themselves have
a genetic (evolutionary) history. He presented an initial figure that
looked something like this:
----> Genes ----> Organism ----> Genes ----> Organism ----> Genes
----> Organism -----> Genes ---->
He emphasized that there is a two way causal interaction between
genotype and phenotype because of evolutionary principles. Phenotype
is the expression of the genotype, but genotype is replication (or
survival to replication) of the phenotype. The environment and complex
behaviors of organisms have a causal role in which DNA sequence we see.
In other words the molecular explanation does not explain survival of
a particular genotype because it does not deal with the whole. The
modus operandi of the biochemist is to break the whole into parts that
in the end destroys the meaning of the whole. I think that the main
point of this part of Haig's presentation was to show that biochemistry
is not the end all that Behe claims it is and that evolutionary
theorists do have something to offer that the biochemist can't touch.
Haig then presented the hemoglobin/myoglobin story (similar to what is
found in my and others' responses to Behe--see on-line reviews listed
above.) Here the emphasis is on sequence comparison, gene duplication,
and novel complex structures arising from previously existing less
complex structures. There is lots of data here from comparative
genetics and comparative biochemistry.
Next, he looked at the structure of ovomacroglobulin--a molecular
"mousetrap" for proteases--a structure that physically traps the
protease in a large cavity in the tetramer after undegoing a
conformational change upon protease binding to the "bait region" (the
protease binding site). He showed how this system of interworking parts
"where the function of the whole is dependent on each part being
present" might have evolved by gradual means. He discussed the
structure of the alpha-2 macroglobulin which has a similar monomer
structure, a bait region, but does not have the tetrameric
conformational change that physically traps the protease in a cavity.
This protein undergoes a conformational change upon protease binding to
the active site that then exposes a reactive thioester that covalently
binds to the protease and disables it. In other words, here is a
functional intermediate on the way to forming the complex molecular
machine.
Finally, he looked at the complement system--one of complex systems
discussed in Darwin's Black Box (131-136). He presented a plausible
scenario, all taken from the biochemical literature, for the evolution
of the complement system, based on evidences of gene duplication and
data from comparative biochemistry. He also noted the interesting
observation that part of this pathway is functioning in fat cells for
unknown reasons, but probably unrelated to immune system function.
My personal opinion is that Haig did the trick. He may not have given
the solution to each one of Behe's unsolved problems, but he showed
that a plausible explanation using known mechanisms could produce the
systems in question.
Of course, Behe's response is "Did not!"
Haig says, "Did so!"
"Did not!"
"Did so!"
...
[TG: Whether someone is convinced depends in part, I think, on their
plausibility threshhold. Perhaps the question should be asked (on both
sides), is there any reason why you want evolution to be true or why
you don't want evolution to be true. People who don't want evolution
to be true because they think it will wreck their theism ought not be
trusted in their plausibility threshhold. People who believe that
evolution must be true because they are atheists ought not be trusted
in their plausibility threshhold. Hmm... whom does that leave?]
[To be continued]
_____________________________________________________________
Terry M. Gray, Ph.D. Department of Chemistry and Biochemistry
Calvin College 3201 Burton SE Grand Rapids, MI 49546
Office: (616) 957-7187 FAX: (616) 957-6501
Email: grayt@calvin.edu http://www.calvin.edu/~grayt
*This mission critical message was written on a Macintosh with Eudora
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A special message for Macintosh naysayers:
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