3TA (was Human and ape phylogeny)

Richard Jensen rjensen at SAINTMARYS.EDU
Wed Apr 9 14:18:19 CDT 2003

I'll play along.  What you are saying is that, if I have data that allow me to
hypothesize that (B,C) is a natural subset of (A,B,C), then there are no additional
data that can be used to test this hypothesis.  Suppose my initial hypothesis is
based on 25 characters.  After a period of rigorous research, I have 5 new
characters and when I include them in the analysis, I now find (total evidence)
that (A,B) is recognized as a natural subset.  My initial hypothesis was put
forward, based on the information then at hand, and was tested with new information
that indicates my initial hypothesis is  inconsistent with the data now at hand.

Why isn't this a test of a hypothesis?


Kirk Fitzhugh wrote:

> Actually, no "test" has been performed. The first inference, leading to
> (A(B,C)), is entirely distinct from the inference leading to (A(B,C)).
> These are different inferences derived from different sets of premises. One
> has nothing to do with the other except to show that one has modified a
> previous inference to take into consideration additional observations in
> need of explanation in the same context as the original observations - this
> is nothing more than abiding by the requirement of total evidence. One
> might claim that they deduced, as consequences of (A(B,C)), additional
> synapomorphies under the guise of a Popperian test. Unfortunately, such a
> deduction is not a valid test since (A(B,C)) will account for those new
> data no matter what. What are of relevance as tests are consequences of the
> causal events claimed by (A(B,C)). Such consequences must be of a class of
> effects independent from the class of effects, i.e., characters, the
> hypothesis is intended to address.
> Kirk
> At 01:19 PM 4/9/03 -0500, you wrote:
> >A phenetic classification is a hypothesis about natural
> >relationships.  What are
> >the relationships among A ,B and C?  Our initial data set yields (A(B,C)).  We
> >"discover" a new set of characters that we believe will help clarify the
> >relationships.  We include these with our initial data and the answer is
> >(A(B,C)).
> >Thus, our initial hypothesis has been tested against the new information
> >and has
> >been found to be consistent with the new information (or, at the least,
> >the new set
> >of characters did not have a strong enough signal to alter the
> >result).  Of course,
> >one could argue that the 250 characters in our first data set completely
> >swamped
> >the signal in the 10 newly discovered characters, but that's another matter
> >entirely.  The second result is based on total evidence and we have no
> >reason to
> >question our hypothesis that (B,C) is a natural group with respect to A.
> >
> >Cheers,
> >
> >Dick

Richard J. Jensen              | tel: 574-284-4674
Department of Biology      | fax: 574-284-4716
Saint Mary's College         | e-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen

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