Model Organisms

Arlin Stoltzfus arlin at is.dal.ca
Fri Apr 25 14:30:38 EST 1997

L.A. Moran wrote:

> >Among trained experts, the
> >word "primitive" means "retaining an ancestral state".  The
> >contrary of "primitive" is "derived".  It is a straightforward
> >matter to apply these terms to individual characters in cases
> >where ancestral states can be inferred.

> I appreciate the point that you are trying to make but perhaps it would be
> best to remember the context. Someone wanted to knw if there were any
> organisms that were more primitive than Drosphila but less primitive than
> C. elegans. Why? Because he was hoping to isolate a C. elegans gene using
> a human probe and was looking for an "intermediate" model organism. Do you
> think that this is a reasonable experiment? Is it consistant with your
> understanding of evolution. (I sure hope not or I have seriously misjudged
> you!)  (-:

Yes, I didn't mean to deny the possibility that the question was 
a bit absurd (I thought that this was implicit at the beginning 
of my statement).  More generally, we could probably all dispense 
immediately, today, with using the words "primitive" and "derived" 
(or its confusing semi-synonym, "advanced") *in reference to 
species or higher taxa* and biology would be none the 
worse for it.  If I were the editor of an evolution journal, I 
would explicitly forbid this usage in the instructions to authors, 
because there is such an extraordinary tendency toward abuse 
(a bit like the words "novel" and "striking" in molecular biology
journals).  Of course we would want to retain these useful 
terms for referring to individual character states.  

I only wanted to warn that the history of evolutionary 
biology (maybe other sciences too) is peppered with instances 
in which the rejection of a false doctrine led to over-generalizations 
that became false doctrines themselves and inhibited research 
in interesting directions.  An example would be the over-heated 
rejection of Lamarckism, orthogenesis and mutationism, which 
leads to blanket statements about mutation being "random" (in 
spite of the obvious evidence that mutation is non-random in 
many ways, including its relationship to fitness-- there 
is usually a bias in favor of fitness-decreasing mutations 
over fitness-increasing ones, as everyone knows) and "spontaneous" 
(in spite of other observations to the contrary).  

Arlin Stoltzfus
Department of Biochemistry
Dalhousie University
Halifax, Nova Scotia B3H 4H7 CANADA
(email) arlin at is.dal.ca 
(phone) 902-494-3569 
(fax) 902-494-1355

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