[Taxacom] Classification of ALL life forms (weblink)

Frederick W. Schueler bckcdb at istar.ca
Thu Apr 22 14:41:47 CDT 2010


Kenneth Kinman wrote:
> Dear All,
>        Last night I forgot to include a weblink to Peter Ward's proposal
> (it apparently also appears in his 2005 book).     Also, note that
> instead of "into the obcells", I meant to type "into the folded-up
> obcells".   Anyway, here's the weblink to Ward's proposal:   
> http://abscicon2006.arc.nasa.gov/abstract/id/159.doc
> ------------------------------------------------------------

* that's very interesting, but I think a more fundamental problem, which 
Ward glosses over, is whether Linnean names can apply to wholly 
artificial life forms, which result from human a priori cleverness 
rather than from historic descent with modification. Do we give a genus 
and species name to the watch that we find ticking on the heath?

fred.
========================================================


> I wrote:
> Dear All, 
>        The relatively new overall classification of life (2005) by Peter
> Ward has apparently not attracted a lot of attention or support, which
> is a very good thing in my opinion, because I don't think the newly
> proposed taxa are particularly natural or useful.  Actually I only 
> stumbled across it today for the first time.            
>        I do agree with him that RNA life preceded present-day DNA-based
> life, and also agree with him that viruses should be classified as
> "life", even if all present-day viruses are probably parasitic. However,
> his classification has a lot of problems: 
>   (1) There is no evidence that cellular RNA forms (his Domain Ribosea)
> ever existed.  Seems more likely that a precellular RNA world evolved
> into a precellular RNA-DNA world before becoming cellularized into the
> obcells (of Cavalier-Smith) or other kinds of protocells.  We may be
> able to synthesize cellular RNA forms in the future, but giving such
> freaks of nature a separate Domain is based on the totally
> unsubstantiated assumption that DNA evolved after cellularization of
> primitive life. 
>   (2)  I also see no advantage in dividing viruses between two
> high-level taxa (his Dominions Ribosa and Terroa).  Some present-day,
> non-cellular RNA viruses may well be just as derived as non-cellular DNA
> viruses).  All types of viruses may have been popping in and out of
> genomes for billions of years, so whether you regard viruses as living 
> or not, it is a polyphyletic grouping no matter how you classify them.
> (3)  Most importantly, if the RNA world preceded the DNA world, 
> and Peter Ward and agree on that, his Dominion Ribosa is not only
> paraphyletic, but paraphyletic in a highly asymmetric (and unuseful)
> way.   So I see this new high-level classification as overly asymmetric,
> unuseful, and as discussed above, probably unnatural.  Therefore the new
> taxonomic category Dominion seems both unnecessary and extremely
> problematic. 
>    Finally, his proposal that Dominions Ribosa and Terroa be 
> combined into a single taxonomic category (Arborea) for earth-based life
> is unneeded.  He not only failed to name the earth-based taxon of rank
> Arborea, I proposed a same taxonomic category back in 1994, named
> Cosmogenre, and gave earth-based life the specific name Cosmogenre
> Geobiota.  I also proposed calling all non-Earth-based life under the
> umbrella term Cosmogenre Exobiota until specific such life forms were
> discovered and described.  If you regard the supposed Martian "fossils"
> found in Antarctica as independently evolved forms of life, I suggested
> that you could perhaps call them Cosmogenre Martiobiota, but I am
> skeptical about these supposed "fossils", so perhaps it is best to wait
> until paleontologists find fossils on Mars (in situ on that planet), a
> couple of decades from now. 
>        In any case, I still prefer classifying viruses and progenotes in
> taxon Parabacteria.  Whether you want to call it a separate Domain or
> Kingdom is one thing, but I find the new higher-level taxonomic category
> (Dominion) neither natural nor useful.  Instead it seems even more
> unnatural and problematic than Woese's Domains.  In both cases, there
> seems to be an implication that they reflect holophyletic taxa (clades)
> when there is no credible evidence to back it up.  Such cladification at
> the highest level is more harmful than helpful.  Frankly, I see them as
> simplistic, deadend, classifications which divert us from a true
> understanding of the early evolution of life.  It is strict
> cladification prematurely run amok (amuck) and is not only unhelpful,
> but harmful in the long run.  I think Peter Ward should be more
> skeptical of Woese's views.  It is best to recognize paraphyly where it
> clearly exists (and is extremely useful) and stop pretending (and
> simplistically ignoring) that such paraphyly is not only useful, but a
> fundamental expression of how the true Tree of Life actually evolved.
> Even if you don't buy this at the species level, it is abundantly clear 
> at broader (especially Kingdom) levels.             
>        ------------Ken Kinman              
> Ward's overall classification of earth-based life: 
> Dominion Ribosa (RNA life) 
>       Domain Viroea (non-cellular RNA viruses) 
>       Domain Ribosea (theoretical, cellular RNA forms) 
> Dominion Terroa (RNA-DNA life) 
>       most Earth life (including some viruses) 
>      NOTE: It is unclear to me if he would put such Terroa viruses in a
> separate Domain from Woese's Three Domains.  In any case, the basal
> Domains of Terroa are almost certainly  paraphyletic, not holophyletic
> (strictly cladistic).  The only Domain that is clearly holophyletic is
> Eukaryota.  I don't find either the proposed phylogeny or the name
> "Terroa" (a real clade??) particularly helpful.  Paraphyletic taxa are
> clearly useful in my opinion, but pretending that such paraphyletic taxa
> are holophyletic (strictly monophyletic) is extremely problematic,
> especially at such high levels of biological classifications. 
> 
> 
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          Frederick W. Schueler & Aleta Karstad
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