[Taxacom] Molecular data and synapomorphies

Pierre Deleporte pierre.deleporte at univ-rennes1.fr
Thu Dec 4 08:34:57 CST 2008

But John, the wording is crucial for efficient communication

your pretended "cladistic data" are just the product of a  
compatibility analysis

if you persist in using "cladistics" instead of "compatibility  
analysis" (see Peter's recent message), and if you talk of your "data"  
without specifying "the subset of available data I selected myself (by  
hand or by nose...) as a (majority???) set of completely compatible  
characters", you will not be understood except by a handful of  
colleagues who patiently struggled their way (since years now...)  
through the arcanes of your astonishingly esoteric vocabulary

what is strange also is that programs are devised for doing exactly  
what you are trying to do by hand (e.g. compatibility analysis in  
Felsenstein's PHYLIP program package, and it's free on the web)

deliberately or not, ignoring the proper terms and tools is a very  
efficient mean for perpetuating largely sterile polemics
but some people like that a lot...

this is not to say that molecular analyses are magic and morphological  
analyses garbadge,
I just mean that e.g. "phenetic data" is pure nonsense, as well as  
"cladistic data", and molecules or morphology can change nothing to that
scientists simply cannot discuss that way
free lectures in systematics are easily accessible on the web for  
anyone willing to make the minimal effort


Quoting John Grehan <jgrehan at sciencebuff.org>:

> I wrote that in the context of the data being generated for a particular
> purpose. If philosophers don't like the wording then I'm ok with
> whatever.
> John Grehan
> ________________________________
> From: J. Kirk Fitzhugh [mailto:kfitzhug at nhm.org]
> Sent: Wednesday, December 03, 2008 8:57 PM
> To: John Grehan
> Subject: Re: [Taxacom] Molecular data and synapomorphies
> John Grehan wrote:
> Perhaps so, but whether the data are capable of answering the same
> question is, for me, the critical problem. If sequence data only provide
> measures of overall similarity (with or without parsimony) then it would
> appear that it cannot address phylogeny in the same way as cladistic
> morphological data.
> "Data" don't answer questions.  The data are what stimulate one to ask
> questions. Sequence data do not provide "measures of overall
> similarity." Sequences are effects in need of explanation no less than
> "morphological data." Even the philosophers of science you want to idly
> chide know that.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> J. Kirk Fitzhugh, Ph.D.
> Curator of Polychaetes
> Invertebrate Zoology Section
> Research & Collections Branch
> Natural History Museum of Los Angeles County
> 900 Exposition Blvd
> Los Angeles CA 90007
> Phone: 213-763-3233
> FAX: 213-746-2999
> e-mail: kfitzhug at nhm.org
> http://www.nhm.org/research/annelida/staff.html
> http://www.nhm.org/research/annelida/index.html
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Pierre Deleporte
UMR 6552 EVE
Station Biologique
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fax 02 99 61 81 88

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