© 2003 by The Society for Integrative and Comparative Biology
Carl Gegenbaur and Evolutionary Morphology
1 Department of Orthodontics University of Washington Seattle, Washington 98195
Carl Gegenbaur and Evolutionary Morphology. UWE HOßFELD, LENNART OLSSON AND OLAF BREIDBACH, EDS. Special Issue, Theory in Biosciences Vol. 122 (2–3), June, 2003, Urban & Fischer
Biology is a fast-moving field that looks forward rather than around, and almost never backward. Thus it is astonishing to be reminded by this little book that with modern evo-devo techniques, we are still asking the same questions that obsessed Carl Gegenbaur, who died a century ago in 1903. Gegenbaur is a little known name, mostly recalled because of the eponymous Gegenbaurs Morphologisches Jahrbuch, a journal which ceased publication in 1990. Yet Gegenbaur, the senior colleague of Ernst Haeckel, was a major figure advocating the scientific study of comparative anatomy and embryology to understand evolution and the founder of the German school of evolutionary morphology. As argued by various authors in this volume, Gegenbaur's views provided the antecedents for later research agendas such as Hennig's cladism (Breidbach) and Spemann's cell lineage criteria for homology (Laubichler and Maienschein).
The volume begins with the editors' contributions, a short biography of Gegenbaur and a history of comparative anatomy (and its divorce from zoology) at the University of Jena. These are followed by papers that set the stage: Göbbel and Schultka's chapter on Gegenbaur's distinguished predecessor, J. F. Meckel the Younger (he of branchial cartilage fame); Ghiselin's colorful tale of the feud between Gegenbaur/Haeckel and Anton Dohrn over Dohrn's (recently revived) theory that vertebrates arose from the annelids; Fröber's account of the anatomical collections on which the Gegenbaur group based their work; and a wonderful summary by Nyhart of the intellectual environment in which the Gegenbaur school first flourished and then faltered. The next articles are those already mentioned by Breidbach and Laubichler/Maienschein, dealing with how Gegenbaur's evolutionary morphology contributed to and conflicted with later work in phylogenetics and embryology.
The next section covers the theories that form Gegenbaur's most famous legacy. The "segmentation theory," as reviewed by Mitgutsch, postulated that the vertebrate head is metameric like the trunk, the cranial nerves being homologous with spinal nerves. Although incorrect in many details, aspects of the segmentation theory are still widely accepted today and form a mainstay of most comparative anatomy courses. Mitgutsch points out that modern work on Hox genes and patterning draws strongly on the organizational basis provided by the segmentation theory. An even better demonstration of the currency of the segmentation theory is the marvelous paper by Kuratani, synthesizing his elegant studies on amphioxus and vertebrate head development in the context of evolutionary transformation. Kuratani favors the dual metamerism promoted by Romer, with head segmentation based on the branchial arches rather than the somites. Olsson reinforces the connection between Gegenbaur and modern evo-devo approaches with a paper on neural crest cell migration in lungfish and amphibians. The final two papers deal with Gegenbaur's "archipterygium theory," that the vertebrate limb is derived from the branchial arches. The archipterygium competed unsuccessfully with the "fin-fold" hypothesis of limb origin, which is the one I learned (as fact) in graduate school. I was therefore very surprised to read in Coates' interesting chapter that there are problems with the fin-fold argument and that certain parts of the archipterygium theory may be right after all. The volume ends with Grandel's explicit linking of the genetics of limb development with Gegenbaur's Bauplan for the limb.
In summary, this collection of papers demonstrates convincingly that modern biology is the product of its roots, and that the oldest questions are still among the most interesting.
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||