From: lambdac-AT-globalserve.net
Date: Fri, 22 Sep 2000 16:54:07 -0500
Subject: 5. Neo-evolutionism and the central dogma of molecular genetics


5. Neo-evolutionism and the central dogma of molecular genetics
Date: Sun, 17 May 1998 14:08:16 -0500
From: lambdac-AT-globalserve.net
Reply-To:  nietzsche-AT-lists.village.Virginia.EDU 
Date: Sun, 17 May 1998 14:08:02 -0500
From: lambdac-AT-globalserve.net
Reply-To: deleuze-guattari-AT-lists.village.Virginia.EDU
------------------------------------------------

(c) 1998 Correa&Correa

A NIETZSCHEAN CRITIQUE OF EVOLUTIONISM, OLD AND NEW
(Doing harm to evolutionism)

5.  Neo-evolutionism and the central dogma of molecular genetics

	What is essential to the Darwinian conception of natural selection is
the accidental nature of the variations - the element of conflict with
Spencer's Social Darwinism, since the fortuitous aspect of variation
*can* be construed to preclude any natural order to evolution (in this
sense, the naturalist Robert Chambers argued that evolution is not
synonymous to progress, since 'good conditions' alone could lead to
progress and 'bad conditions' to degeneration).  Neo-Darwinism returns
over and over to this point - that only accidental changes that occur at
the level of the genome can be conserved once they are phenotypically
selected by the environment.  The mutations randomly come *before* the
selection.  Specifically, these changes depend upon filiation for their
transmission (the greatest progeny...) and upon reproduction for their
generation - hence the *central* importance (for officiating
evolutionary biology) of the rates of mutation during the 'growth
phases' of populations when reproduction is maximal.

	This is the fundamental basis for all the modern theories of heredity -
from the bacterium to metazoic systems, variation occurs by random
spontaneous mutation of genomic DNA in the replicative phase of the cell
cycle, or via the meiotic reductions of gametes coupled to their fusion
in the zygote.  (...)  Ever since Weismann's XIXth century theory of
heredity, it became taboo to suppose that acquired variations could be
directly transmitted.  Experience or any internal force, save the force
of heredity, could be ruled out as playing any role in the evolution of
species.  The evolution of coordinated and apparently purposeful organs
became seen as merely the result of a gradual accumulation of random
mutations in the genomic structure, all of which would occur during DNA
replication.  Essentially, natural selection operated at the level of
the phenotype, only indirectly selecting the most adequate genotype
which in turn had been randomly generated.  There is thus no need to
suppose acquired characteristics or directed mutation.
	(...)
	The paradigm for the foundation of neo-Darwinism is the microbiological
Luria-Delbrück distribution.  A decade before the elucidation of DNA
structure, Luria exposed log-phase E. coli cultures to the Lambda phage
and observed that there was a random variation in the number yielded by
each colony of mutant bacteria resistant to lysis by the phage. 
Utilizing S. Luria's analogy of the slot machine as a model for the
observed frequency of spontaneous mutation, the physicist and
mathematician M. Delbrück worked out a stochastic analysis that
predicted a Poisson distribution (characteristic of events which are
improbable but nevertheless occur if a large number of trials are
sampled) for the observed frequencies of spontaneous mutation in a
sample of cultures.  An average rate of mutation could then be predicted
on the basis that mutation was random and not directed, since the
observed numbers were not constant from culture to culture.  Then the
Lederbergs, in 1952, confirmed Luria's findings and showed that bacteria
which had never been exposed to antibiotics could still give rise to
resistant mutations in the absence of any environmental pressure.  This
was interpreted as solid evidence for the random nature of the mutation
process.
	(...)
	The stochastic model of genomic transformation during the mitotic phase
of log growth dovetailed with what has become, since J. Watson and F.
Crick's paper, the central dogma of molecular genetics: that the flow of
genetic information is a one way street, from DNA  to RNAs to proteins. 
Logically, the only mutations of consequence to heredity would be those
that occurred at the level of genomic DNA, and this tenet immediately
privileged replication as the domain of mutagenesis.  Prominent
scientists - even J. Monod - categorically stated that the flow of
information in reverse was simply inconceivable.  Maynard Smith went to
the core of the problem when he said that "what a Lamarckian must do is
disprove the [central] dogma" of molecular genetics.

	The random nature of the mutations became explained by biochemical
studies of errors in the functioning of a battery of enzymes
(polymerases, primases, replicases, gyrases, ligases, etc) involved in
the replication and repair of genomic DNA, particularly with the
'proof-reading' functions of polymerases.  Misrepair (base
substitutions, mispairing and frameshift mutations) and DNA replication
errors were thus seen as the major sources of random mutagenesis.  
	(...)
	The first shock, which neo-evolutionism has by now almost completely
absorbed, was the discovery of reverse transcriptase (RT) by H. Temin's
group (including P. Duesberg), reported in 1970.  Identified in
oncogenic retroviruses, RT synthesized complementary DNA from an RNA
template - breaking the first rung of the dogma: information also flowed
in reverse from RNA to DNA.  (...)  Since then, evidence has accumulated
indicating that RT is present in both eukaryotic and prokaryotic cells -
where its role still remains far from clear.  

	Temin's views on the significance of retroviruses went as far as
suggesting that they functioned as intercellular messengers with a role
in differentiation and "could provide part of a mechanism for
inheritance of some acquired characters".  This view challenged what
later became known as the oncogenic theory of retroviruses - since
Temin's views demanded that we question whether retroviruses and their
involvement in specific oncogenic processes functioned - in the
traditional sense of Koch's postulates, as agents or causes of disease. 
Furthermore, by raising the spectrum of neo-Lamarckism with the notion
of a postadaptive role for retroviruses, Temin was begging the very
physiological basis for the malignant transformation of cells: could
Warburg have been onto something when he argued that cancer was a
mutagenic process driven by oxygen starvation?  Reich never ceased
pointing that out.

	Clearly, like all dogmas, the DNA dogma of neo-evolutionist molecular
genetics was a leaky one.  But even researchers of the caliber of J.
Monod hurried to patch the leaky dogma as if nothing had happened-

	"(...) the transcription step from DNA to RNA  (...) is nothing
surprising.  (...) Even by the basic principle in physical chemistry, of
the reversibility of microscopic events, it could be predicted that such
events could occur.  They do occur, indeed, but this must not be taken
to mean that information from protein could possibly go back to the
genome.  I think, despite some hesitation even by very some very
distinguished colleagues, that I am ready to take any bet you like that
this is never going to turn out to be the case!"


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