Learning from history: Morphology's challenges in Germany ca. 1900

Abstract

A century ago, Carl Gegenbaur's program of vertebrate evolutionary morphology faced its greatest challenges. The controversy over the evolutionary origin of the vertebrate paired limbs between 1875 and 1906 illustrates the failure of the traditional methods of comparative anatomy and embryology (supported by Haeckel's biogenetic law) to choose between different phylogenetic hypotheses. The controversy over morphology's status as science intensified at the turn of the twentieth century, when the legitimacy of historical explanation itself as a mode of scientific understanding came under fire. Gegenbaur's intellectual grandson, Hermann Braus, sought to defend the legitimacy of phylogenetic reconstruction while updating it to include experimental and causal-analytical approaches, but was unable to sustain a viable synthetic research program. The article concludes with reflections on approaches to the past used by historians and evolutionary morphologists.

The importance of the “Gegenbaur school” for German morphology

“…The controversy over method assumed concrete form in the debate that raged between 1875 and about 1910 over the origin of the limbs. Gegenbaur's school mobilized to support Gegenbaur's``gill archº theory against the``fin-foldº theory proposed by the American James K. Thacher, developed by the British morphologist St. George Mivart, and supported by numerous German morphologists, including Robert Wiedersheim, Carl Rabl, and Anton Dohrn (Nyhart 1995(Nyhart , 2002Bowler 1996). Thus Michael von Davidoff, who was conducting research in Gegenbaur's lab while he worked as an assistant in Heidelberg's zoology institute, produced (1879) an article in the Morphologisches Jahrbuch analyzing the pelvic fins, which concluded with an attack on the fin-fold theory ± an analysis that Gegenbaur himself, using his prerogative as the journal's editor, backed up with a short note of support appended to the article.…”

Kowalevsky, comparative evolutionary embryology, and the intellectual lineage of evo‐devo

“…We refer to this intellectual lineage as comparative evolutionary embryology and its most natural contrast in historical context is developmental mechanics (Entwicklungsmechanik), which took as one of its starting points an explicit rejection of the methodology inherent in the phylogenetic problem agenda at that time. Wilhelm Roux, Hans Driesch, and others attempted to forge a causal investigation of development that did not entangle itself in phylogenetic speculations (Oppenheimer,'67,, which appeared to repeatedly end in stalemates (Nyhart, 2002). The rhetoric of the superiority of experimental embryology over the painstaking descriptive observations most commonly associated with comparative evolutionary embryology coincided with a general trend towards experimentalism in the early 20th century (Allen,'76).…”

What is the promise of developmental evolution? III. The crucible of developmental evolution

“…By the end of the 19th century, however, evolutionary morphology had lost its ability to recruit a critical mass of young scientists and thus lost much of its momentum. Lynn Nyhart has argued that the reason for the loss of evolutionary morphology's prominent status was, in part, the inability of its practitioners to agree on standards of evidence to evaluate the veracity of evolutionary scenarios (Nyhart, '95;Nyhart, 2002). Specifically, there were no methods to evaluate the primacy of anatomical versus developmental data for any particular evolutionary hypothesis, leaving the researcher to rely only on personal bias.…”

“…Examples are the controversies over the origin of paired appendages in vertebrates (Nyhart,'95) and the role of segmentation of the vertebrate head (Kuratani, 2003;Mitgutsch, 2003). This led to heated personal debates that ultimately convinced the younger generation that the field was not very promising (Nyhart, 1995;Nyhart, 2002).…”