Hennig-Rosa connection

[John Grehan]

Michael Schmitt comments:

 >The name of the second author is clearly given on this page as 'Bernd
 >Hennig'. Dr. Bernd Hennig (Freiburg im Breisgau, Germany) is Willi
Hennig's second son.

I somehow missed the second name, but now see it.

The
 >>author's acknowledge suggestions that during this time Hennig learned
 >>Rosa's theory.
 >This does not mean that they (or I) think this to be likely.

I agree. The point is that the possibility is admitted. I am not suggesting
that Hennig necessarily did have this opportunity to read Rosa's works,
only that it might have.

 >Rosa published a paper in French in 1923 which he called a 'summary' of
the 1918 book. I have carefully read this paper. Provided that it reflects
 >correctly the content of the 1918 book, it is clear that this book is
 >irrelevant to Willi Hennig's method of Phylogenetic Systematics.

Given that there are similarities in the method of Rosa and Hennig,
Rosa's hologenesis is relevant.

 >I can only add that, according to the 1923 summary, there are two points
in Rosa's ideas superficially resembling aspects of Hennig's method:
 >1) Rosa stated that there is a 'law of ramification'
 >2) Rosa was of the opinion that of the two descendant lineages always one
 >will cange evolutionarily at a higher rate than the other.

Whether such similarities are "superficial" or not may be a matter
of individual opinion. Certainly the works of Rosa and Hennig are not
identifical. Authors such as Luzzato et al have pointed to the
the presence of the same analytical concepts present in the work of Rosa
and Hennig. Conceptual differences between their respective theoretical
models do not alter the fact of these similarities. Further, I would not
suggest or imply that the two approaches are identical or that Hennig
has not improved on Rosa (e.g. Schmitt's reference to the lack of criteria
by Rosa for distinguishing "linea precoce" and "linea tardiva").

I agree with Schmitt that the matter of whether Hennig read Rosa is
speculation. The speculation arises because of the level of similarities
between their respective works. These similarities are historically
interesting, however they came about.

John Grehan