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AW: Notarium question
evelyn sobielski writes:
> > If you score them differently on the assumption that they are
> > separate apomorphies, then you're assuming what you're setting
> > out to prove.
> On the other hand, if you score simply "notarium present (y/n)?",
> you may not be able to show they are separate apomorphies *even if
> they were* because your scoring assumes that the notarium is a
> monolithic entity - which any cladistic analysis will try to
> optimize towards a single origin.
That is exactly what you want: the analysis will balance the
desirability of parsimony of the notatium (single origin, no
reversals) with that of all the other characters. Like I said, you do
the analysis to _discover_ whether this (and other characters) have a
single origin or multiple origins.
> (This is the mistake that led Cracraft to "prove" that
> Hesperornithes, loons and grebes are a clade to the exclusion of
> all other birds living and extinct. In the case of the notarium,
> its presence was used to argue for the monophyly of "Metaves" -
> which, as it seems now, are almost certainly a pseudoclade. For a
> similar error, consider the fallacy "everything with feathery
> integument is a member of Aves".)
I am not familiar with Cracraft's work, but it sound like his problem
was not an a priori assumption that the notarium has a single origin,
but over-emphasizing one "important" character to the neglect of
others that tell a different story.
And notice anyway that assuming a single origin of the notatium, as
you say Cracraft did, is a _completely_ different thing from scoring
the presence of a notarium as a single character and leaving it up to
the analysis to determine how many origins that character had in the
most parsimonious trees. That's the whole point: we try not to assume
_anything_: just make observations, and let the computer turn its
wheels and tell us what those observations indicate about the
> This need not yield "better" results (i.e. better-supported and
> less polytomies). But uncertainty that is correct is preferrable to
> certainty that is wrong.
No argument there!
/o ) \/ Mike Taylor <firstname.lastname@example.org> http://www.miketaylor.org.uk
)_v__/\ "These lions you saw. Did they ... eat ants?" / "Yes, that's
right." / "No, those weren't lions you saw. They were anteaters"
-- Monty Python's Flying Circus.