Re: Rapid Lizard Evo

[dinoboygraphics@aol.com]

There were a few classic misconceptions in Dan's post I wanted to 
clarify: the majority of random mutations are niether harmful nor 
beneficial, most do not impact survival and reproductive success at 
all.  Ones that do often have small impacts (e.g. a basepair 
substitution in a transcription promoter may make the protein may alter 
the affinity towards it's binding site, making a gene cascade turn on 
slightly sooner or later).  These help rack up small phenotypic 
variations in general proportions which mostly don't matter but become 
selection-worthy when the environment changes (e.g. the larger heads of 
the lizards in the study under consideration).

Random mutations most certainly play a large roll in maintaining this 
type of overall phenotypic variation, and said variety is constantly 
acruing (albeit being weeded out too if the phenotype strays too far 
into contra-adaptive territory which provides the base variation that 
natural selection acts upon.

Dan is right that organisms that use sexual reproduction certainly 
leverage genetic recombination to increase the degree of phenotypic 
variation in a population (and in the case of strong selection it may 
also let a succesful trait proliferate more rapidly to the rest of the 
population).  Also true that organisms with complex central nervous 
systems can buffer themselves against selection on their genomes by 
altering behavior, and this is especially succesful in organisms that 
can transmit learned behaviors.

It should be noted, however, that the vast majority of organisms cannot 
utilize one or both of these buffers, so the accumulation of random 
genetic variation into the genome still provides the majority of 
variation that is acted upon by selection in the history of life.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com


-----Original Message-----
From: Dann Pigdon <dannj@alphalink.com.au>
To: dinosaur@usc.edu
Sent: Tue, 22 Apr 2008 5:23 pm
Subject: Re: Rapid Lizard Evo

Â
One of the worst generalisations about evolution is that it mostly 
involves random genetic mutations over long periods of time. I suspect 
that random mutation plays only a very small part in the evolutionary 
process, and that other processes (recombination, RNA interferance, 
learned behaviour, to name a few) provide far more fodder for natural 
selection to act on, and on a much smaller time scale. Â
Relying on random mutation is fine, as long as those mutations are 
actually beneficial (which most aren't), and as long as your 
environment doesn't change faster than *beneficial* random mutation can 
keep up with (which it almost certainly will). Otherwise you'd better 
have some short-term backup plans just in case. Â
___________________________________________________________________ Â
Dann PigdonÂ
GIS / Archaeologist http://geo_cities.com/dannsdinosaursÂ;
Melbourne, Australia http://heretichides.soffiles.comÂ;
___________________________________________________________________Â