Farewell to Species - reticulation

Michael Schmitt m.schmitt at UNI-BONN.DE
Wed Feb 2 10:37:21 CST 2000

At 11:25 01.02.2000 -0600, Thomas Lammers wrote:
>Submitted for mulling over: cladistics is flawed science because it comes
>to a conclusion first ("all evolution is dichotomously divergent, with
>ancestors becoming extinct at the appearance of a pair of daughter-taxa")
>and then seeks data to support that conclusion.

THIS is a widespread misconception. Cladistics - at least as long as it is
understood in  the "classical" sense of phylogenetic systematics does NOT
start from the "conclusion" that "all evolution is dichotomously
divergent". Instead, the search for dichotomous splittings is a METHODICAL
demand arising from pure logics: if a species splits, the result are at
least two lineages; if we end up in our analysis with a polytomy there is
absolutely no change to exclude definitely the possibility that this
polytomy is actually a non-resolved sequence of dichotomies; if we,
however, end up with a dichotomy - based on synapomorphies - then it is
extremly unlikely that we did overlook a real polytomy.

Nothing else can be found in Willi Hennig's papers, and I am pretty certain
that no present-day cladist would ever argue in favour of a 'law of
dichotomous splitting' or something similar.


* Dr. Michael Schmitt (Zoologischer Anzeiger, Managing Editor) *
* Zoologisches Forschungsinstitut und Museum Alexander Koenig  *
* Adenauerallee 160, D-53113 Bonn, Germany                     *
* Phone/Fax +49 228-9122 286, e-mail: m.schmitt at uni-bonn.de    *
* http://www.uni-bonn.de/museumkoenig/ENGLISH/ESCHMITT.HTML    *

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