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  Topic: The Canonical Genetic Code, Resources & arguments< Next Oldest | Next Newest >  

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Joined: May 2002

(Permalink) Posted: May 30 2002,01:49   

Reviewing this 1993 article by Paul Nelson and Jonathan Wells:


Is Common Descent an Axiom of Biology?

[Editorial note:  The following discussion paper was written for the conference, “The Darwinian Paradigm: Problems and Prospects,” held June 22-25, 1993, at the Pajaro Dunes beach community on Monterey Bay, near Watsonville, California.  The conference was organized by Phillip Johnson.  Attendees included Michael Behe, Walter Bradley, John Angus Campbell, William Dembski, Dean Kenyon, Stephen Meyer, Paul Nelson, David Raup, Siegfried Scherer, Jonathan Wells, and Kurt Wise.]


To:                  Pajaro Dunes Conference Participants
From:              Paul Nelson and Jonathan Wells
Date:               15 June 1993
Re:                  Discussion paper for Topic Area I (homology, etc.)

...and skipping to the genetic code section, we find that Nelson & Wells are indeed assuming that the "functional invariance" thesis was dropped, without evidence, to protect common descent:


The Universal Genetic Code Argument for Common Descent

Lest it be thought that this pattern of reasoning – namely, sacrificing the auxiliary theory to save common descent – is an isolated example, we offer another, perhaps more striking case.

Most of us are familiar with the universal genetic code argument for common descent.  The argument first appeared in the mid to late 1960s, after the structure of the code was elucidated.  It is now widespread.[33]

[they quote several quotes to this effect]

...and then, they argue that "functional invariance" is highly probable and therefore scientists are unjustifiably dropping the "functional invariance theory" to protect common descent:


Postulating that such fundamental variations occurred is, however, very far from knowing how they occurred. "Direct replacements of one amino acid by another throughout proteins," argue Osawa et al., "would be disruptive in intact organisms and even in mitochondria."[45]  That is, we should not think that the body of molecular knowledge motivating functional invariance can be jettisoned at will. (Yes, if common descent is true, and variant codes exist, functional invariance has to go to the wall. Yet functional invariance still seems to be true, or at least highly probable.)  Rather, taking common descent as given, we are now faced with another novel research problem: "How could non-disruptive code changes occur?"[46]

I find this article fascinating because it exemplifies one particularly devious tactic of the ID movement: rather than taking the obvious, but difficult, route of simply arguing that common descent is true or false to some specific degree, based on this and that specific evidence, they try to make the convert the entire argument into one about the intellectual credibility of the biologists, and therefore the thesis the IDists are really trying to advance is something like "mainstream biologists are biased and would believe in evolution no matter what the evidence."  As in Nelson & Wells' conclusion:


Suppose Darwin had it right, namely, that "all the organic beings which have ever lived on this earth have descended from some one primordial form."[52]  The existence of this "one primordial form," the common ancestor, establishes a theoretical domain that logically subsumes all biological and paleontological phenomena.  That is, even if life had multiple origins, we will be unable, having assumed the truth of common descent, to provide any evidence for that possibility: all observed organisms, whether recent or extinct, will necessarily lie within what might be called the "common ancestor horizon."

If this seems counter-intuitive, try the following thought experiment. Assume the truth of common descent, and then attempt to construct an empirical argument against it. No imaginable evidence one might bring to bear, however striking – e.g., organisms for which no transitional stages seem possible, multiple genetic codes – will be able to overturn the theory. If there really was a common ancestor, then all discontinuities between organisms are only apparent, the artifacts of an incomplete history. An ideally fine-grained history would reveal the begetting relations by which all organisms have descended from the common ancestor.

If the axiom thesis is correct, then the theory of common descent will indeed be refractory to the evidential challenges thrown up by biological experience. One can see the point in Mayr's recent claim that common descent

has been gloriously confirmed by all researches since 1859. Everything we have learned about the physiology and chemistry of organisms supports Darwin's daring speculation that "all the organic beings which have ever lived on this earth have descended from some one primordial form..."[53]

One wonders what we could have learned about organisms, since 1859, that would not have confirmed common descent.

We offer the axiom thesis, not because we are persuaded of its truth, but to provide a starting point or focus for discussion. How, really, do the patterns of living things count for, or against, the notions of primary continuity (common ancestry) or primary discontinuity (polyphyly)? If common descent cannot be dislodged by the "evidence," then how should we go about evaluating it?

I propose a (new??) term for this style of argument: Argumentum ad Innuendo.

Thanks, nic

Edited by niiicholas on May 30 2002,01:51

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