[Taxacom] SUSPECT Re: Molecules vs Morphology

[Stephen Thorpe]

Just a small point here, but scientists have an odd definition of  
'definition'! Evolution cannot be 'defined' (in the true,  
philosophical sense of 'defined') as change in genome because it was  
an empirical discovery that genomes even exist, nevermind that they  
have anything at all to do with evolution! Actually, though,  
'evolution' is a vague theoretical notion with little in the way of  
meaning. What we are trying to explain is BIODIVERSITY! Creationists  
have their own "theory" to "explain" it. "Evolutionists" have very  
different theories, such as genetic change (with accompanying  
reproductive isolation) combined with geological events (vicariance),  
dispersal, etc. etc. It seems bizarre to me to distinguish between  
morphological and genetic evolution when they are both just two  
aspects on one explanation of biodiversity...

As Tony would say, just my 2 cents ...

Stephen

Quoting Mario Blanco <mblanco at flmnh.ufl.edu>:

> Commonly accepted among biologists in general. That definition has
> absolutely no conflict with morphological evolution. As I said, all
> morphological evolution is determined by changes in the genetic makeup
> through generations. I am myself more interested in the morphology, but
> even paleontologists have to acknowledge the genetic basis of
> morphological evolution. The reason that this definition does not
> explicitly mention morphology is because you can have genetic change
> through generations without any obvious change in morphology or
> behavior. And yes, that is still evolution.
>
> Of course, when you study evolution of extinct taxa you have to rely on
> morphological evolution and rarely (if at all) can study the underlying
> genetic changes, but that doesn't mean they didn't occur. The logical
> assumption is that all morphological changes were determined by genetic
> changes. And of course, you can have artifacts, like when different life
> stages or sexes are mistakenly taken as different species, always a risk
> with extict taxa (and any poorly known extant taxa for that matter).
>
> If you define evolution in terms of morphological change, then you have
> to be careful to explicitly indicate that such change must be heritable
> (to avoid Lamarckian implications). And of course, "heritable change"
> implies that it is dictated by the genome.
>
>
> Bob Mesibov wrote:
>> Mario Blanco wrote:
>>
>> "But evolution itself is defined as change in the genetic makeup of  
>> a population through generations (this is a widely accepted  
>> definition of evolution)."
>>
>> Ouch. Widely accepted among phylogeneticists, maybe, but  
>> paleontologists would disagree. Also all those who, like me, have a  
>> rather more richly textured picture of evolutionary history than a  
>> set of gene trees.
>>
>
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