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

Posts: 97
Joined: May 2002

(Permalink) Posted: May 30 2002,12:59   

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.

That's got to be the stupidest argument I've ever seen.  If common descent is true, then there will be no empirical evidence against it.  What they're basically saying is "true theories can't be shown to be false empirically".  Why don't they just say that differing genetic codes are empirical evidence against common descent and be done with it?  How does it make sense to construct a thought experiment where we try to hold two contradictory notions at once, i.e., common descent is both true and shown to be false by the evidence?

Anyway, Nelson & Wells' contention that biologists dropped the "no viable intermediates" claim in order to protect common descent is demonstrably false.  It was dropped because it was shown to be wrong, empirically.  Not only does the example of ambiguous codes demonstrate this, but also the ability of researchers to alter the codes of living organisms.  Ironically, the DI aticle that responds to Miller alludes to this:

Experiments to change the identity of transfer RNA (tRNA)--another possible mechanism by which genetic codes might reassign codon “meanings”--have shown that the intermediate steps must be bridged by intelligent (directed) manipulation. In one such experiment, for instance, Margaret Saks, John Abelson, and colleagues at Caltech changed an E. coli arginine tRNA to specify a different amino acid, threonine. They accomplished this, however, only by supplying the bacterial cells (via a plasmid) with another copy of the wild-type threonine tRNA gene. This intelligently-directed intervention bridged the critical transition stage during which the arginine tRNA was being modified by mutations to specify threonine. [6]

Notice that they're trying to do with this experiment what they do with animal and plant breeding.  When mutation and selction are shown to be sufficient to cause substantial morphological change, they dismiss it outright because it was really just "intelligent design" even though it has nothing to do with ID as they conceive it.  And here, the ability of the code to change is dismissed because it was caused by "intelligent design", as if plasmid transfers never happen in the wild.    

Anyway, here are the refs for the papers cited:

6. Margaret E. Saks, Jeffrey R. Sampson, and John Abelson, “Evolution of a Transfer RNA Gene Through a Point Mutation in the Anticodon,” Science 279 (13 March 1998):1665-1670.

7. Jennifer Normanly, Richard C. Ogden, Suzanna J. Horvath & John Abelson, “Changing the identity of a transfer RNA,” Nature 321 (15 May 986):213-219.

I haven't read them as I don't have online access to either journal (though I might just get off my butt and walk the 100 yards to the library.)  I am interested in seeing how these papers compare to the DI quote-mining spin.


P.S.  Just noticed that the DI has a typo in their reference for the Normanly et al paper.  It looks like it's from 1986, in which case they're using a reference that's much too old given that they're lots of recent ones.

  14 replies since May 23 2002,08:35 < Next Oldest | Next Newest >  


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