Biochemical Challenge

Ron Grunwald grun at acpub.duke.edu
Fri Nov 8 03:15:14 EST 1996


In article <wgallin.1197790122A at news.srv.ualberta.ca>,
wgallin at gpu.srv.ualberta.ca (Warren Gallin) wrote:

> In Article <55ta2t$vtn at fidoii.cc.lehigh.edu>, inpri at lehigh.edu (Alan
> Allegra) wrote:
> >Just out of curiosity, has anyone read the book, "Darwin's Black Box:  The 
> >Biochemical Challenge to Evolution," by Lehigh University professor Michael 
> >Behe? It is a convincing challenge to the theory of Darwinian evolution.
> >
> 
> I haven't read the book, but I did here Behe propounding his theories on CBC
> radio a couple months ago.
>     His arguments boiled down to (I paraphrase) "I can not understand how it
> could work, so it can't work".  I find this argument by personal
> incomprehension to be less than compelling.

I did read the recent NYT Op-Ed piece, though. I assume that the argument
there pretty much follows the book. As a teacher of cell biology and
biochemistry I find his "argument by personal incomprehension" (nice
phrase, btw) just a bit distressing as well as weak. For in his
unwillingness to wrestle intellectually with the remarkable complexity of
the modern cell Behe deprives his students of the excitment and richness
that comes from building evolutionary explanations of complex systems. 

Ironically, declarations such as "it's so complex that it can only be the
act of a devine intelligence" disuade a young student from asking the
probing how and why questions of biochemical systems right at a time when
we have the tools and an expanding knowledge base that allows such
questions to be asked fruitfully. He does a great disservice by declaring
the mystery and complexity of microscopic world to be dark and
impenetrable!

To his credit, he does bring to the fore one of the more challenging
problems of evolutionary thinking, that of 'pre-adaptation' or the
difficulty in explaining the evolution of complex systems adapted for
novel functions. This was the problem that Darwin raised in his discussion
of the evolution of the eye, now so often misrepresented by creationists
like Behe. 

Indeed, we teach in sophmore (freshman?) biology courses that this is
exactly the challenge of modern biology - to explain the emergence of such
complex structures as the eye or the bacterial flagellum (Behe's example)
without resorting to teleology.  That we cannot (at least I cannot) spin a
neat Darwinian narrative about origins of the bacterial flagellum should
simply be an acknowledgement of ignorance and of the enormity of the
challenge ahead of us - not literal proof of the workings of a devine
engineer. 

The fact is that good Darwinian explainations are possible, even now, for
the origins of many complex biochemical systems. For example, the origins
of the  'irreducibly complex' system of oxidative phosphorylation
(electron transport chains, ATP synthases, = dozens of proteins +
impermeant membranes) may be thought of in terms of the independent
evolution of H+ extruding proteins which conferred tremendous selective
advantage to the acidifying cells of an early anaerobic world.  

The fortuitous co-localization of several such pumps in a the same
membrane may result in the remarkable emergence of an entirely new trait -
the chemiosmotic activation of ADP->ATP. It is not necessary to suggest
that such chemiosmotic systems were 'designed' to produce ATP - this is
clearly not the case. And yet the chemiosmotic activation of ATP surely
offered a significant selective advantage for the fortunate few and has
had profound consequences for the subsequent evolution of life. 

The story is a familar one we teach the freshmen. It may, of course, be
all wrong - that is the nature of historical explanations. But how much
more exciting are they than the cowardly retreat into incomprehension!

-- 
Ron Grunwald 
Department of Botany
grun at acpub.duke.edu                            



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