Re: Classification: A Definition

[Tim Williams <twilliams_alpha@hotmail.com>]

Colin McHenry wrote:

> Hang on, I think this is a little unfair on Linnaeanists.  Whilst the old 
> system was absolutely and >horribly biased towards multicellular 
> eukaryotes, I don't think it's fair to say that this was due to >the ills 
> of the Linnaean system.  [snip] The two kingdom classification that many of 
> us were taught >[snip] was a result of ignorance stemming from the lack of 
> the right tools, not the fault of the classification system.

I've got nothing against the way things used to be done, given that these 
were different times.  But the old system is just that: the "old system".  
Modern tools have revealed just how inadequate the old Linnaean system was.  
I don't blame the Linnaean microbiologists; it's not their fault that they 
didn't have PCR and thermocyclers and electron microscopy.  Similarly, for 
previous generations of "macrobiologists", it's not their fault that they 
didn't have high-powered computers to plug-and-chug away at huge character 
matrices.  We're spoiled, in this day and age.

There is a context here, and I actually agree with you about the "March of 
Science" changing many of our traditional views.  I agree that Linnaean 
classification did the best it could, and it was a convenient system for 
categorizing the diversity of life.  Unfortunately, many of its hallmarks 
(e.g., the use of ranks; mutually exclusive groups for ancestors and 
descendents) was fundamentally misleading.  New research and new techniques 
show just how creakingly inappropriate Linnaean classification is to 
describe and portray phylogenetic relationships.

> So to claim that our improved understanding of basic diversity is thanks to 
> thanks to people abandoning Linnaeus is something I would dispute.

I agree.  I would say that abandoning the Linnaean classification system is 
a by-product of our improved understanding of basic diversity.

> Insistance of the importance recognising major monophyletic groups?  Sure.

Seconded.

> Committment to abandoning ranks?  No.

Here I would disagree.  Linnaean names can stay (Aves, Mammalia, etc), but 
not ranks (above genus, or maybe family, anyway).  And no more splitting off 
of certain groups from their ancestors into separate "classes" or "phyla" - 
such as birds separate from theropods, or mammals from therapsids 
("mammal-like reptiles"), or pogonophoran worms from polychaetes.

> Of course, if Margulis is right about the eukaryote cytoskeleton being a 
> result of endosymbiosis >with a spirochaete-type bacteria, then the Eucarya 
> are merely a symbiosis between one branch of >the Bacteria and one branch 
> of the Archea.  I'm still confused about how the Phylocode will deal with 
> these sorts of tree topologies;

So am I.  At the root of Eucarya/Bacteria/Archaea life resembles one big 
rugby scrum.

Cheers

Tim

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