Darwin (was: Phylogenetic evidence)

[Peter Stevens]

Those interested in Darwin and classification might want to read

Kevin Padian, "Charles darwin's views on classification in theory and
practice".  Syst. Bio. 48: 352-364. 1999.

As to what CD would think if he were alive today, I will consult my
medium.  If it is printable, I will let you know.

P.

>Barry,
>      I detect no hint of any complaint (about ranks) in Darwin's statement.
>  Could this be wishful thinking on your part?  :-)
>      Seems to me he is making a straightforward observation about how to
>"express" differential anagenesis (different degrees of modification) in a
>classification.  And this can be just as true for molecular data as it is
>for morphological data.
>     It's perfectly natural to give two sister groups different rank based
>on  different degree of divergence.  The therapsid Family Tritheledontidae
>went extinct early on and therefore had no chance to diverge nearly as far
>as its sister group Class Mammalia.  Likewise a genus can be a sister group
>to a whole family or even an order.  I see no problem with this as long as
>you explicitly show such sister group relationships (as I do with my exgroup
>markers).
>     Seems to me Darwin is just acknowledging that this is the way it was
>done and there would have been no need to "endorse" it.  And this is still
>done, in spite of strict cladism's efforts to demonize and snuff out
>paraphyly completely.  If you really think Darwin was a proponent of
>unranked taxonomy, I would think you could find a more direct statement in
>his many writings.  I don't recall any indication that he would have
>preferred unranked classifications, nor do I have any reason to believe he
>would prefer strict cladism if he were alive today.
>         ------ Cheers,  Ken
>***************************************
>>From: Barry Roth <barry_roth at YAHOO.COM>
>>Reply-To: Barry Roth <barry_roth at YAHOO.COM>
>>To: TAXACOM at USOBI.ORG
>>Subject: Re: Phylogenetic evidence
>>Date: Wed, 10 Jul 2002 09:03:14 -0700
>>
>>Ken,
>>They say the Devil can cite scripture for his purposes.  Let's see.  In
>>your linked message you quote Darwin thus:
>>
>>       "but that the amount of difference in the several branches or
>>groups,
>>though allied in the same degree in blood to their common progenitor, may
>>differ greatly, being due to the different degrees of modification which
>>they have undergone; and this is expressed by the forms being ranked under
>>different genera, families, sections, or orders."  (Origins of Species,
>>Chapter 13)
>>
>>
>>I read this as Darwin's insight that morphology is an imprecise guide to
>>degree of consanguinity and his recognition that the standard, ranked
>>classification is based on "magnitude of difference" in morphology, not
>>phylogeny.  He states that this is the case; he doesn't necessarily endorse
>>it.  In fact, his statement is a complaint about the problem.
>>
>>
>>
>>I therefore claim Darwin as an early proponent of unranked taxonomy.
>>
>>
>>BR (adjusting his horns)
>>
>>
>>  Ken Kinman wrote:Barry,
>>I wholeheartedly agree with Darwin on this, but this is only a partial
>>quote, and omits an extremely important qualifier (which strict cladists
>>often prefer to ignore).
>>See my post on this subject in January 2001 at the DML (dinosaur
>>mailing list). Here's the link:
>>
>>http://www.cmnh.org/dinoarch/2001Jan/msg00328.html
>>
>>
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