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Author Topic:   Irreducible complexity at the microscopic level
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 15 of 27 (426921)
10-09-2007 3:23 AM


Evolution's forgotten prediction
Genetic Variablity, Twin Hybrids and Constant Hybrids, in a Case of Balanced Lethal Factors, by Hermann J Muller:
quote:
In the first place, it is likely that lethals are really among the common-
est forms of mutants, but they would be discovered much more readily
if they were dominant in regard to some visible character than if they
were completely recessive, and this would cause the proportion of lethals
among the dominant mutant factors to appear to be excessively high,
when compared with the proportion among the recessives. Most pres-
ent-day animals are the result of a long process of evolution, in which
at least thousands of mutations must have taken place. Each new mu-
tant in turn must have derived its survival value from the effect which
it produced upon the "reaction system" that had been brought into being
by the many previously formed factors in cooperation; thus a compli-
cated machine was gradually built up whose effective working was de-
pendent upon the interlocking action of very numerous different ele-
mentary parts or factors, and many of the characters and factors which,
when new, were originally merely an asset finally became necessary
be-
cause other necessary characters and factors had subsequently become
changed so as to be dependent on the former. It must result, in conse-
quence, that a dropping out of, or even a slight change in any one of
these parts is very likely to disturb fatally the whole machinery;
for this
reason we should expect very many, if not most, mutations to result in
lethal factors, and of the rest, the majority should be "semi-lethal" or
at least disadvantageous in the struggle for life, and likely to set wrong
any delicately balanced system, such as the reproductive system.
Although this conclusion had suggested itself to the writer in 1912 it
would manifestly have been very difficult to obtain experimental evi-
dence for it...
(My emphasis)
"Irredicible Complexity" was a prediction based upon evolutionary theory made in 1912 by Nobel Prize winner, Hermann Muller. I think it is important to get that across. I may have more to say directly linked to the OP, and I'll edit that in if I get the time.
Edited by Modulous, : No reason given.

Replies to this message:
 Message 18 by Kitsune, posted 10-09-2007 12:07 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 22 of 27 (426990)
10-09-2007 12:25 PM
Reply to: Message 18 by Kitsune
10-09-2007 12:07 PM


Re: Evolution's forgotten prediction
I take it that the author was not quite right there, and that mutations tend not to be as commonly harmful as he suggests. Otherwise we would not see organisms evolving as they have done.
He was surprisingly accurate. Most genetic mutations that have an effect on the phenotype...on the biochemistry, are harmful. A suitably complex biochemical structure is much more likely to be ruined by even a slight change than it is to be improved. Populations tend to find themselves either evolving in light of environmental change, or more generally they find themselves in equilibrium - all the phenotypes are generally clustered around an optimum, and deviating from the optimum is likely to result in selection culling things back. It's only when the optimum changes that we see the mutations that might make the organism less badly adapted for the new environment.

This message is a reply to:
 Message 18 by Kitsune, posted 10-09-2007 12:07 PM Kitsune has not replied

  
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