Cladistic hypotheses

Thu Nov 24 14:58:29 CST 2005

Bravo, Kirk! In Sys. Zool. 31: 100-104 (1982!) I pointed out that "testing" one hypothesis with another is nonsense. At best it can only CONFIRM, but never REFUTE; as I wrote then "Ultimately one is just counting the score: the number of consistent hypotheses". Maybe, though, one can use the "Inference to the Best Explanation" model.

Don Colless,
Div of Entomology, CSIRO,
GPO Box 1700,
Canberra. 2601.
Email: don.colless at csiro.au
Tuz li munz est miens envirun

-----Original Message-----
From:   Taxacom Discussion List on behalf of J. Kirk Fitzhugh
Sent:   Thu 11/24/2005 4:39 AM
To:     TAXACOM at LISTSERV.NHM.KU.EDU
Cc:	
Subject:             Re: Cladistic hypotheses
At 10:17 AM 11/23/2005 -1000, you wrote:
>I didn't entirely understand Kirk's message that prompted this, but as I
>see it, you test the cladogram by running an analysis and determining if
>it is the best one available according to whatever criteria (parsimony,
>ML, Bayesian, etc.) you are using.  Of course this is all automated so
>that the "hypotheses" are generated automatically.  The only thing that
>seems unusual (in terms of deviating from typical scientific theory) is
>that a hypothesis (i.e. cladogram) can't really be falsified on its own
>but only when you find another one that has better support.

Unfortunately, there is nothing within the inference of cladograms,
regardless of what software one uses or mental inclination one has, that
has anything at all to do with testing.  The long-standing notion that one
cladogram can test/falsify another cladogram is mistaken.  One cladogram
based on data set a+b+c cannot be evaluated against a cladogram based on
data set a+b+c+d (or even mutually exclusive data sets).  The two
hypotheses stand independent of one another as entirely different causal
explanations for different sets of causal questions.

Kirk

-----------------------------------------------------
J. Kirk Fitzhugh, Ph.D.
Curator of Polychaetes
Invertebrate Zoology Section
Research & Collections Branch
Los Angeles County Museum of Natural History
900 Exposition Blvd
Los Angeles CA 90007

Phone:   213-763-3233
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e-mail:  kfitzhug at nhm.org
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