Traits and/or states

Kirk Fitzhugh kfitzhug at NHM.ORG
Fri Oct 31 11:31:23 CST 2003


At 10:42 AM 10/31/03 +0100, you wrote:
>The character/state distinction seems to be (to me, at least) reasonable
>not only from the purely practical point of view.
>What we call 'character' and 'state' in the phylogenetic analysis are
>indeed both high-level constructs, not observations (not speaking about
>all the problems with the process of "observation"). The character/state
>distinction is a way how to hierarchize such constructs; we can treat this
>hierarchic relation as a subject/predicate, variable/value or whatever but
>the language we are using can hardly change the merit. I have personally
>found nothing in your message (nor in your presentation referenced below)
>what would contradict this generally accepted opinion. Perhaps you could
>explain your position in more detail?


My thanks to Drs. Skala and Deleporte for their thoughtful comments. I will
try to respond here to both.

I'm not entirely sure I understand what is meant by "high-level
constructs." If descriptions of organisms, or the cells of a data matrix,
do not represent our observations, then it would be difficult to claim that
a phylogenetic hypothesis is an explanation of shared similarities.

The concern I have had with the "character" and "state" distinction is that
it is not consistent with the nature of observation. What we observe are
objects by way of their properties (= character, attribute, trait), and
these are communicated by subject-predicate relations. For instance, I
cannot observe "number of digits." But I can observe that the distal ends
of some set of appendages (subject) have five digits (predicate). The
"character," "number of digits," and the "state," "five," cannot represent
subject-predicate relations denoting observations since "number of digits"
does not represent the subject observed. What are observed are subjects
called appendages with the property (= character, attribute, trait) of five
digits. The cell of a data matrix for species X must code the observation
that individuals in this class have appendages with five digits. The cell
is not simply a "state;" the cell summarizes observations.

I don't find any hierarchic relation here, and such a relation would not be
expected for objects and their properties. On the other hand, an object can
be composed of subsidiary objects, in which case hierarchic relations can
be stated. But, this hierarchic relation of a part composed of parts is not
equivalent to the observations which allow us to speak of the relation itself.

I hope this helps clarify what I said earlier.

Best,

Kirk

-----------------------------------------------------
J. Kirk Fitzhugh, Ph.D.
Associate 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
FAX:     213-746-2999
e-mail:  kfitzhug at nhm.org
http://www.nhm.org/research/annelida/index.html
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