Uwe Hoßfeld

The synthetic theory of evolution: general problems and the German contribution to the synthesis

A metatheoretical and historiographical re-analysis of the Evolutionary Synthesis (the process) and the Synthetic Theory (the result) leads to the following conclusion: The Synthetic Theory is not a reductionistic, but rather a structuralistic theory with a limited range of relevant hierarchical levels. Historically the Synthesis was not a sudden event but a rational long-term project carried out between 1930 and 1950 by a large number of biologists in several countries. In the second part of our paper the contributions of several German biologists to the Synthesis are analyzed.

The Road from Haeckel: The Jena Tradition in Evolutionary Morphology and the Origins of "Evo-Devo"

With Carl Gegenbaur and Ernst Haeckel, inspiredby Darwin and the cell theory, comparativeanatomy and embryology became established andflourished in Jena. This tradition wascontinued and developed further with new ideasand methods devised by some of Haeckel’sstudents. This first period of innovative workin evolutionary morphology was followed byperiods of crisis and even a disintegration ofthe discipline in the early twentieth century.This stagnation was caused by a lack ofinterest among morphologists in Mendeliangenetics, and uncertainty about the mechanismsof evolution. Idealistic morphology was stillinfluental in Germany, which prevented a fullappreciation of the importance of Darwin’stheory of natural selection for comparativemorphology. Evolutionary morphology andembryology failed to contribute significantlyto the modern synthesis of evolutionarybiology, thereby probably delaying theintegration of developmental biology intomodern evolutionary biology. However, Haeckel’sstudent Oscar Hertwig, as well as Victor Franzand Alexej N. Sewertzoff from a youngergeneration, all tried to forge their ownsynthetic approaches in which (inspired byHaeckel’s work) embryology played an importantrole. Important for all three researchers wereattempts to refine, and sometimes redefine, thebiogenetic law, and to find new scientificexplanations for it (and for the manyexceptions to it). Their research was latermore or less forgotten, and had littleinfluence on the architects of the modernsynthesis. As the relationship betweenevolutionary and developmental biology is nowagain rising in importance in the form of“Evo-Devo”, we would like to draw attention tohow this earlier research tradition grappledwith similar questions to those now on theagenda, albeit from sometimes quite differentperspectives.

Evolutionary developmental biology: its concepts and history with a focus on Russian and German contributions

Evolutionary theory has been likened to a “universal acid” (Dennett 1995) that eats its way into more and more areas of science. Recently, developmental biology has been infused by evolutionary concepts and perspectives, and a new field of research—evolutionary developmental biology—has been created and is often called EvoDevo for short. However, this is not the first attempt to make a synthesis between these two areas of biology. In contrast, beginning right after the publication of Darwin’s Origin in 1859, Ernst Haeckel formulated his biogenetic law in 1872, famously stating that ontogeny recapitulates phylogeny. Haeckel was in his turn influenced by pre-Darwinian thinkers such as Karl Ernst von Baer, who had noted that earlier developmental stages show similarities not seen in the adults. In this review, written for an audience of non-specialists, we first give an overview of the history of EvoDevo, especially the tradition emanating from Haeckel and other comparative embryologists and morphologists, which has often been neglected in discussions about the history of EvoDevo and evolutionary biology. Here we emphasize contributions from Russian and German scientists to compensate for the Anglo-American bias in the literature. In Germany, the direct influence of Ernst Haeckel was felt particularly in Jena, where he spent his entire career as a professor, and we give an overview of the “Jena school” of evolutionary morphology, with protagonists such as Oscar Hertwig, Ludwig Plate, and Victor Franz, who all developed ideas that we would nowadays think of as belonging to EvoDevo. Franz ideas about “biometabolic modi” are similar to those of a Russian comparative morphologist that visited Jena repeatedly, A. N. Sewertzoff, who made important contributions to what we now call heterochrony research—heterochrony meaning changes in the relative timing of developmental events. His student I. I. Schmalhausen became an important contributor to the synthetic theory of evolution in Russia and is only partly known outside of the Russian-reading world because only one of his many books was translated into English early on. He made many important contributions to evolutionary theory and we point out the important parallels between Schmalhausen’s ideas (stabilizing selection, autonomization) and C. H. Waddington’s (canalization, genetic assimilation). This is one of the many parallels that have contributed to an increased appreciation of the internationality of progress in evolutionary thinking in the first half of the twentieth century. A direct link between German and Russian evolutionary biology is provided by N. V. Timoféeff-Ressovsky, whose work on, e.g., fly genetics in Berlin is a crucial part of the history of evo-devo. To emphasize the international nature of heterochrony research as predecessor to the modern era of EvoDevo, we include Sir G. R. de Beer’s work in the UK. This historical part is followed by a short review of the discovery and importance of homeobox genes and of some of the major concepts that form the core of modern EvoDevo, such as modularity, constraints, and evolutionary novelties. Major trends in contemporary EvoDevo are then outlined, such as increased use of genomics and molecular genetics, computational and bioinformatics approaches, ecological developmental biology (eco-devo), and phylogenetically informed comparative embryology. Based on our survey, we end the review with an outlook on future trends and important issues in EvoDevo.

The history of the oldest self-sustaining laboratory animal: 150 years of axolotl research.

Today the Mexican axolotl is critically endangered in its natural habitat in lakes around Mexico City, but thrives in research laboratories around the world, where it is used for research on development, regeneration, and evolution. Here, we concentrate on the early history of the axolotl as a laboratory animal to celebrate that the first living axolotls arrived in Paris in 1864, 150 years ago. Maybe surprisingly, at first the axolotl was distributed across Europe without being tied to specific research questions, and amateurs engaged in acclimatization and aquarium movements played an important role for the rapid proliferation of the axolotl across the continent. But the aquarium also became an important part of the newly established laboratory, where more and more biological and medical research now took place. Early scientific interest focused on the anatomical peculiarities of the axolotl, its rare metamorphosis, and whether it was a larva or an adult. Later, axolotl data was used to argue both for (by August Weismann and others) and against (by e.g., Albert von Kölliker) Darwinism, and the axolotl even had a brief history as a laboratory animal used in a failed attempt to prove Lysenkoism in Jena, Germany. Nowadays, technical developments such as transgenic lines, and the very strong interest in stem cell and regeneration research has again catapulted the axolotl into becoming an important laboratory animal.

The architects of the evolutionary synthesis in national socialist Germany: science and politics

The Synthetic Theory of Evolution (SyntheticDarwinism) was forged between 1925 and 1950.Several historians of science have pointed outthat this synthesis was a joint venture ofSoviet, German, American and Britishbiologists: A fascinating example of scientificcooperation, considering the fact that theevolutionary synthesis emerged during thedecades in which these countries were engagedin fierce political, military and ideologicalconflicts. The ideological background of itsAnglo-American representatives has beenanalyzed in the literature. We have examinedthe scientific work and ideological commitmentsof the German Darwinians during the ThirdReich. We based our analysis on four criteria:1) General attitude towards the Third Reich. 2) Membership in the NSDAP and other nationalsocialist organizations. Endorsement anddisapproval of the state ideology in 3) scientific and 4) other publications. We willmainly discuss the various authors that havecontributed to Die Evolution derOrganismen (1943), a collection thatrepresented the evolutionary synthesis inGermany. Most of the authors promoted eugenicideas, but not all of them adopted the racistinterpretation of the Third Reich. Anotherfinding is that there existed no directconnection between party membership andpromotion of the state ideology.

Psychoontogeny and psychophylogeny: Bernhard Rensch’s (1900–1990) selectionist turn through the prism of panpsychistic identism

Toward the end of the 1930s, Bernhard Rensch (1900–1990) turned from Lamarckism and orthogenesis to selectionism and became one of the key figures in the making of the Synthetic Theory of Evolution (STE). He contributed to the Darwinization of biological systematics, the criticism of various anti-Darwinian movements in the German lands, but more importantly founded a macroevolutionary theory based on Darwinian gradualism. In the course of time, Rensch’s version of the STE developed into an all-embracing metaphysical conception based on a kind of Spinozism. Here we approach Rensch’s “selectionist turn” by outlining its context, and by analyzing his theoretical transformation. We try to reconstruct the immanent logic of Rensch’s evolution from a “Lamarckian Synthesis” to a “Darwinian Synthesis”. We will pay close attention to his pre-Darwinian works, because this period has not been treated in detail in English before. We demonstrate an astonishing continuity in topics, methodology, and empirical generalizations despite the shift in Rensch’s views on evolutionary mechanisms. We argue that the continuity in Rensch’s theoretical system can be explained, at last in part, by the guiding role of general methodological principles which underlie the entire system, explicitly or implicitly. Specifically, we argue that Rensch’s philosophy became an asylum for the concept of orthogenesis which Rensch banned from evolutionary theory. Unable to explain the directionality of evolution in terms of empirically based science, he “pre-programmed” the occurrence of human-level intelligence by a sophisticated philosophy combined with a supposedly naturalistic evolutionary biology.

The History of Comparative Anatomy in Jena – an Overview

Comparative anatomy and zoology both have long academic traditions in Jena. At first, the two subjects developed in parallel and had many similarites in research topics. This development is covered in the first part of the paper. The close relationship between the two subjects started to break apart when Carl Gegenbaur and Ernst Haeckel were active at Jena University. In 1865 Haeckel became the first full professor of zoology in Jena, and zoology became more independent from comparative anatomy. In the second part of our paper, we follow the developments in comparative anatomy in Jena from Gegenbaur’s immediate students up until the end of Hans Boker’s tenure in Jena in the mid-1930s. Certain subjects are in focus throughout this period, for example vertebrate head morphology and development, (the “head problem”), the relationship between anatomy and biology, and evolutionary questions. Some of these subjects have remained important research topics in zoology and comparative anatomy in Jena until the present day.

Major Research Traditions in Twentieth-Century Evolutionary Biology: The Relations of Germany’s Darwinism with Them

Evolutionary theory has been likened to a “universal acid” (Daniel Dennett) that erodes its way into more and more areas of science. Yet, every single branch of biology has developed this context with its own specific characteristics, which, either through hindering or promoting, has affected the national scientific developments in evolutionary biology. We will argue that the Darwinian theories interacted with national research traditions such that the resulting conceptual body represented an amalgamation of a metatheoretical framework with the “purely empirical” theoretical beliefs such as the theory of natural selection. We will demonstrate this using the example of the German research tradition in evolutionary biology. We will analyse this German tradition comparing it to other major traditions in evolutionary biology such as the English- and Russian-speaking evolutionism. The problem of specific influences constituting the German, English-language (Great Britain and the USA), and Russian-language context of the first and the second Darwinian revolutions will be addressed. In addition, we will introduce a concept of “metaparadigm” reflecting the specificity of German evolutionary theory at the time of the first and the second Darwinian Revolutions.

Preface. Between Ernst Haeckel and the homeobox: the role of developmental biology in explaining evolution

The importance of embryonic development for evolutionary biology has been an issue ever since Charles Darwin and Ernst Haeckel, however, Modern Synthesis approaches to evolution have often neglected certain aspects of developmental biology or treated development as a black box (Mayr and Provine 1980; Breidbach and Ghiselin 2007a, b). Although Wallace’s statement that ‘‘problems concerned with the orderly development of the individual are unrelated to those of the evolution of organisms through time’’ (Wallace 1986, p. 149) is extreme, midtwentieth century mainstream evolutionary biology did not feel much need for an integration of developmental biology into its theoretical foundations. The fact that evolutionary questions have been of interest to some developmental biologists between the era of Darwin and Haeckel and the 1980s, i.e., that modern evolutionary developmental biology, or Evo-devo, as the field is often called by its practitioners, in fact has a history, has received relatively little attention. It has even been claimed that ‘‘Following a quiescent period of almost a century, present-day Evo-devo erupted out of the discovery of the homeobox on the 1980s’’ (Arthur 2002, p. 757). Thus, there is a need for more research into the period ‘‘between Ernst Haeckel and the homeobox’’ in order to gain a more complete understanding of the roots of modern Evo-devo. We are helped by the recent upsurge in interest in the history of Evodevo, which has produced several edited volumes (e.g., Laubichler and Maienschein 2007) and thematic issues of journals. Also this journal has contributed to this increased publication activity on the pre-history and history of Evodevo, having had thematic issues (Theory in Biosciences 124:259–420; 126:115–175) on different aspects of the subject. The history of Evo-devo in the Anglo-American world has received renewed attention recently, as exemplified, e.g., by the work of Alan Love (e.g., Love 2003, 2006; Love and Raff 2003), whose scheme of the historical development of the relationship between evolution and development is here reproduced as Fig. 1. We have ourselves concentrated on the history of Evo-devo in the Germanand Russian-speaking countries (e.g., Hossfeld and Olsson 2003; Levit et al. 2004, 2006; Olsson et al. 2006; Breidbach and Ghiselin 2007a, b; Reis et al. 2007). In Love’s scheme (Fig. 1), he contrasts the ‘‘textbook version’’ (left) with an improved, updated version (right). In the left diagram, evolutionary biology is split from developmental biology, which was dominated by ‘‘Entwickelungsmechanik’’ (Developmental Mechanics) in the first third of the twentieth century. The developmental biologist Thomas H. Morgan (1866–1945) is seen as an example of the split between experimental embryology and genetics, which he helped to found and develop into molecular genetics. Another part of genetics, population genetics, became an important part of the Modern Synthesis of evolutionary biology (Mayr and Provine 1980; L. Olsson (&) Institut fur Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-Universitat Jena, Erbertstr, 1, 07743 Jena, Germany e-mail: Lennart.Olsson@uni-jena.de

Adolf Remane (1898–1976) and his views on systematics, homology and the Modern Synthesis

Adolf Remane was primarily a morphologist and systematist. In 1952, he published an influential book on the foundations of systematics and phylogenetics in which he advocated homology as the central concept of morphology and the basis of the natural system and discussed criteria serving to discriminate homology from homoplasy in great detail. During the decades when the Modern Synthesis of evolution was created, he repeatedly commented on and criticised the synthetic theory of evolution, which he never fully accepted. Remane disapproved of idealistic morphology and was strongly opposed to Lamarckian, saltationist and orthogenetic theories of evolution. Yet, while appreciating the synthetic theorys validity in the realm of speciation and microevolution, he rejected the claim that the current genetic knowledge was sufficient to explain complex morphological transformations on the basis of random mutations and selection. Instead, he seems to have favoured mutation pressure as the most important factor in macroevolution. Nevertheless, the sometimes vicious disputes between Remane and the adherents of the Modern Synthesis may at least partly have been brought about by personal factors rather than by scientific differences.