Darwin, Haeckel, and the "Mikluskan gas organ theory".

A previously unknown reference to the Russian ethnologist, biologist, and traveler Nikolai N. Miklucho-Maclay (1846-1888) was discovered in correspondence between Charles Darwin (1809-1882) and Ernst Haeckel (1834-1919). This reference has remained unknown to science, even to Miklucho-Maclay's biographers, probably because Darwin used the Russian nickname "Mikluska" when alluding to this young scientist. Here, we briefly outline the story behind the short discussion between Darwin and his German counterpart Haeckel, and highlight its importance for the history of science. Miklucho-Maclay's discovery of a putative swim bladder anlage in sharks, published in 1867, was discussed in four letters between the great biologists. Whereas, Haeckel showed enthusiasm for the finding because it supported (his view on) evolutionary theory, Darwin was less interested, which highlights the conceptual differences between the two authorities. We discuss the scientific treatment of Miklucho-Maclay's observation in the literature and discuss the homology, origin, and destiny of gas organs-swim bladders and lungs-in vertebrate evolution, from an ontogenetic point of view. We show that the conclusions reached by Miklucho-Maclay and Haeckel were rather exaggerated, although they gave rise to fundamental insights, and we illustrate how tree-thinking may lead to differences in the conceptualization of evolutionary change.

The biogenetic law and the Gastraea theory: From Ernst Haeckel's discoveries to contemporary views.

More than 150 years ago, in 1866, Ernst Haeckel published a book in two volumes called Generelle Morphologie der Organismen (General Morphology of Organisms) in the first volume of which he formulated his biogenetic law, famously stating that ontogeny recapitulates phylogeny. Here, we describe Haeckel's original idea as first formulated in the Generelle Morphologie der Organismen and later further developed in other publications until the present situation in which molecular data are used to test the "hourglass model," which can be seen as a modern version of the biogenetic law. We also tell the story about his discovery, while traveling in Norway, of an unknown organism, Magosphaera planula, that was important in that it helped to precipitate his ideas into what was to become the Gastraea theory. We also follow further development and reformulations of the Gastraea theory by other scientists, notably the Russian school. Elias Metchnikoff developed the Phagocytella hypothesis for the origin of metazoans based on studies of a colonial flagellate. Alexey Zakhvatin focused on deducing the ancestral life cycle and the cell types of the last common ancestor of all metazoans, and Kirill V. Mikhailov recently pursued this line of research further.

Ernst Haeckel, Nikolai Miklucho-Maclay and the racial controversy over the Papuans.

BACKGROUND: The "German Darwin" Ernst Haeckel (1834-1919) was a key figure during the first "Darwinian revolution", a time when the foundations of the modern evolutionary theory were laid. It was Haeckel, who crucially contributed to the visualization of the Darwinian theory by designing "genealogical-trees" illustrating the evolution of various species, including humans. Although the idea of explaining human evolution by natural selection belongs to Darwin, Haeckel was the first who attempted to create a new exact anthropology based on the Darwinian method. DISCUSSION: Trying to immediately reconstruct human evolution proceeding from the description of modern populations led Haeckel to the views which, from the contemporary perspective, are definitely racist. Haeckel created racial anthropology intending to prove human origins from a lower organism, but without the intention of establishing a discriminatory racial praxis. Although hierarchical in its outcome, the Haeckelian method did not presuppose the necessity of a racial hierarchy of currently living humans. It is crucial to grasp in what sense Haeckel's theoretical explorations in human evolution were racist, and in what sense they were not. Our argument flows as follows. One of Haeckel's pupils was the Russian ethnographer, anthropologist and zoologist Nikolai Nikolajewitsch Miklucho-Maclay (1846-1888). Maclay and Haeckel worked closely together for several years; they traveled jointly and Maclay had enough time to learn the major methodological principles of Haeckel's research. Yet in contrast to Haeckel, Maclay is regarded as one of the first scientific anti-racists, who came to anti-racist views using empirical field studies in Papua-New Guinea. CONCLUSIONS: We claim that while conducting these studies Maclay applied scientific principles to a significant extent acquired from Haeckel. The paper contributes to the view that Haeckel's theoretical racism did not follow the Darwinian method he used.

100 Years of phenogenetics: Valentin Haecker and his examination of the phenotype.

Following the 'rediscovery' of Mendel's work around 1900 the study of genetics grew rapidly and multiple new inheritance theories quickly emerged such as Hugo de Vries' "Mutation Theory" (1901) and the "Boveri-Sutton Chromosome Theory" (1902). Mendel's work also caught the attention of the German geneticist Valentin Haecker, yet he was generally dissatisfied the simplicity of Mendelian genetics as he believed that inheritance and the expression of various characteristics appeared to be much more complex than the proposed "on-off hypotheses". Haecker's primary objection was that Mendelian-based theories still failed to bridge the gap between hereditary units and phenotypic traits. Haecker thus set out to bridge this gap in his research program, which he called Phänogenetik ("phenogenetics"). He outlined his work in a special study "Entwicklungsgeschichtliche Eigenschaftsanalyse (Phänogenetik)" in 1918. 2018 thus marks the 100th anniversary of Haecker's seminal publication, which was devoted to the analysis of the phenotype and highlighted the true complexity of heredity. This article takes a specific look at Haecker and his work, while also illustrating how this often forgotten scientist influenced the field of genetics and other scientists.

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 reception of Haeckel in pre-revolutionary Russia and his impact on evolutionary theory.

The "German Darwin" Ernst Haeckel was influential not only in Germany, but in non-German-speaking countries as well. Due to the widespread use of German as a language of science in the Russian Empire along with growing Russian-German links in various scientific fields, Haeckel directly and indirectly influenced Russian intellectual landscape. The objective of the present paper is to investigate Haeckel's impact on Russian biology before the Bolshevik Revolution of 1917. We outline the transfer of Haeckelian ideas to Russia and its adaptation to a national research tradition. Haeckel's ideas influenced the most crucial Russian evolutionists such as brothers Alexander and Vladimir Kovalevsky, Ilya (Elias) Metschnikoff, Mikhail Menzbier (Menzbir), Karl Kessler, Andrei Famintzyn, and Konstantin Mereschkowsky. At the same time, Haeckel's speculative hypotheses and his attempts to convert Darwinism into a universal worldview by promoting monism found little support in biological circles of Russia. Russian biology grew as an empirical science having weak connections to "romantic philosophy" as German biology did. This, among others, explains the acceptance of Haeckel as a biologist and the rejection of Haeckel as a philosopher by crucial Russian evolutionists.

Ernst Haeckel in the history of biology.

The German zoologist Ernst Haeckel (1834-1919) was arguably the most influential champion of Darwin's theory of evolution on the European continent and one of the most significant worldwide. As his biographer Robert Richards emphasized: "More people at the turn of the century learned of evolutionary theory from his pen than from any other source, including Darwin's own writings" [1]. Furthermore, Darwin himself considered Haeckel a crucial proponent of his theory. How can we explain the mismatch between Haeckel's extraordinary influence among his contemporaries and his relatively modest place in the current historiography of biology? Why are Haeckel-studies nothing like the 'Darwin-industry'? To answer these questions, we outline Haeckel's contribution to evolutionary biology and anthropology and - to a lesser extent - the general history of ideas. We argue that Haeckel is currently underestimated, because history written by the advocates of the modern synthesis focused on neo-Darwinian schools of thought and neglected 'old-school-Darwinism' which Haeckel was part of. Besides, Haeckel's militant anti-clericalism and his exotic philosophy of 'monism' made him an uncomfortable figure in European intellectual history. In contrast to Darwin, Haeckel from the very beginning tried to turn Darwinism into a universal worldview, thus jeopardizing his credibility as a scientist.

Ernst Haeckel (1834-1919): The German Darwin and his impact on modern biology.

The year 2019 marks the 100th anniversary of the death of Ernst Haeckel, a German zoologist, artist, and philosopher of science, who defended and supplemented Charles Darwin's system of theories regarding the mechanisms of biological evolution. We briefly recapitulate Haeckel's remarkable career and reproduce the Laudatio read by the President of the Linnean Society of London (1 July 1908), when Haeckel was awarded the Darwin-Wallace Medal. Finally, we summarize the importance of Haeckel's original concepts, insights, and theories with reference to our current knowledge in the areas of evolutionary biology, molecular phylogenetics, systematic zoology, and philosophical issues today.

Ernst Haeckel's contribution to Evo-Devo and scientific debate: a re-evaluation of Haeckel's controversial illustrations in US textbooks in response to creationist accusations.

As Blackwell (Am Biol Teach 69:135-136, 2007) pointed out, multiple authors have attempted to discredit Haeckel, stating that modern embryological studies have shown that Haeckel's drawings are stylized or embellished. More importantly, though, it has been shown that the discussion within the scientific community concerning Haeckel's drawings and the question of whether embryonic similarities are convergent or conserved have been extrapolated outside the science community in an attempt to discredit Darwin and evolutionary theory in general (Behe in Science 281:347-351, 1998; Blackwell in Am Biol Teach 69:135-136, 2007; Pickett et al. in Am Biol Teach 67:275, 2005; Wells in Am Biol Teach 61:345-349, 1999; Icons of evolution: science or myth? Why much of what we teach about evolution is wrong. Regnery Publishing, Washington, 2002). In this paper, we address the controversy surrounding Haeckel and his work in order to clarify the line between the shortcomings and the benefits of his research and illustrations. Specifically, we show that while his illustrations were not perfect anatomical representations, they were useful educational visualizations and did serve an important role in furthering studies in embryology.

Ecology and Evolution: Haeckel's Darwinian Paradigm.

Ernst Haeckel coined the term ecology in the process of Darwinizing our understanding of nature. His concept of ecology was part of a theoretical system embracing development, evolution, and environment. We outline Haeckel's views on ecology as an evolutionary science and demonstrate their importance for current theoretical developments.

Evolutionary ethics and Haeckelian monism: the case of Heinrich Schmidt's Harmonie (1931).

This paper offers the first ever published discussion of the ethical treatise Harmonie: Versuch einer monistischen Ethik [Harmony: an attempt at a monistic ethics] by Heinrich Schmidt (1874-1935), one of the leading figures in the circle of Ernst Haeckel. Published near the end of Schmidt's life (1931), it constituted a kind of summation of decades of intense involvement in the "project" of German monism that found its epicentre in Jena, and in Haeckel's attempts at founding it on Darwinian and Goethian lines. After a brief description of Schmidt's life and works, we summarize the main lines of Haeckel's evolutionary thought and their expression in his sparse ethical writings. A detailed description of Harmonie follows, in which we seek to demonstrate Schmidt's close adherence to Haeckel's monist foundations, as well as indicate where he expanded his own thinking in directions beyond Haeckel's. Lastly, we suggest that Harmonie, perhaps contrary to Schmidt's wishes after 1933, nevertheless offers textual evidence of the deep incompatibility of Schmidt's understanding of ethics to the sociopolitical ideology of National Socialism. This is consistent with the historical record of how Haeckel's monism, together with those like Schmidt who worked tirelessly to promote it, was negatively regarded by the NSDAP.

Ernst Haeckel's embryology in biology textbooks in the German Democratic Republic, 1951-1988.

In our era of computers and computer models, the importance of physical or graphical models for both research and education in developmental biology (embryology) is often forgotten or at least underappreciated. Still, one important aspect of embryology is the (evolutionary) developmental anatomy of both human and animal embryos. Here, we present a short history of the visualization of Ernst Haeckel's "biogenetic law" and his "gastraea theory" in biology textbooks from the German Democratic Republic (GDR) between 1951 and 1988. Our analysis of GDR textbooks showed embryology was integrated into different disciplines and remained an educational constant within the school textbooks throughout the GDR despite various educational reforms. While the majority of these textbooks failed to reference either Ernst Haeckel or his contributions to embryology, they often did mention Haeckel in sections dedicated to the theory of evolution and the promotion of Soviet ideals such as materialism.

The "Biogenetic Law" in zoology: from Ernst Haeckel's formulation to current approaches.

150 years ago, in 1866, Ernst Haeckel published a book in two volumes called "Generelle Morphologie der Organismen" (General Morphology of Organisms) in which he formulated his biogenetic law, famously stating that ontogeny recapitulates phylogeny. Here we describe Haeckel's original idea and follow its development in the thinking of two scientists inspired by Haeckel, Alexei Sewertzoff and Adolf Naef. Sewertzoff and Naef initially approached the problem of reformulating Haeckel's law in similar ways, and formulated comparable hypotheses at a purely descriptive level. But their theoretical viewpoints were crucially different. While Sewertzoff laid the foundations for a Darwinian evolutionary morphology and is regarded as a forerunner of the Modern Synthesis, Naef was one of the most important figures in 'idealistic morphology', usually seen as a type of anti-Darwinism. Both Naef and Sewertzoff aimed to revise Haeckel's biogenetic law and came to comparable conclusions at the empirical level. We end our review with a brief look at the present situation in which molecular data are used to test the "hour-glass model", which can be seen as a modern version of the biogenetic law.

Valentin Haecker (1864-1927) as a pioneer of phenogenetics: Building the bridge between genotype and phenotype.

Valentin Haecker is one of the forerunners of experimental biology, genetics, and developmental physiology. Haecker introduced the term Phänogenetik (phenogenetics) in 1918 in Entwicklungsgeschichtliche Eigenschaftsanalyse (Evolutionary Analysis of Characters), in which he described the earliest stages in the development of the phenotype. 1 His major objective in this publication was to integrate the 2 most important concepts of Mendelian genetics-phenotype and genotype-within a well-articulated theory. Haecker realized that a proper analysis of how the genotype gives rise to the phenotype requires the integration of knowledge of morphology, physiology, and experimental embryology.

The First Darwinian Phylogenetic Tree of Plants.

In 1866, the German zoologist Ernst Haeckel (1834-1919) published the first Darwinian trees of life in the history of biology in his book General Morphology of Organisms. We take a specific look at the first phylogenetic trees for the plant kingdom that Haeckel created as part of this two-volume work.

Beyond borders: on the influence of the creationist movement on the educational landscape in the USA and Russia.

This paper provides a detailed look at how creationism originated in the United States and then explores how this evangelical trend was exported to Russia by American missionaries following the fall of the USSR. The comparison between these two countries is particularly interesting since the rivalry between the US and the USSR during the race to space caused both countries to revamp their science education. Yet, while political interests led both governments to focus on science education, creationist activities were simultaneously focused on diminishing the coverage of evolution in science classrooms. Now, decades following Sputnik's trip to space, the urgency to strengthen scientific learning has waned, while creationists are still equally focused on removing scientific naturalism in favor of supernatural explanations for the origin of species. This paper thus offers an in-depth look at which groups are currently responsible for promoting creationist activities in the US and in Russia and which groups are working hard to keep supernatural doctrines out of science curriculum.