Ernst Haeckel in the history of biology

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.

Phylogenies in yeast species descriptions: in defense of neighbor-joining

The neighbor-joining (NJ) method of tree inference is examined, with special attention to its use in yeast species descriptions. How the often-vilified method works is often misunderstood. More importantly, given the right kind of data, its output is a phylogram that illustrates a hypothetical phylogeny that is just as credible as that obtained by any other method. And as with any other method, the result is greatly affected by sampling intensity, particularly the number of aligned positions used for analysis. I address various allegations, including the claim that the method is phenetic, and therefore not phylogenetic. I argue that NJ is the most suitable tree inference method to use in yeast species descriptions, primarily because it is best at visually preserving the extent of sequence divergence between close relatives, which continues to be the primary criterion for yeast species delineation. The relevance of bootstraps in application of the phylogenetic species concept is discussed. This article is protected by copyright. All rights reserved.

Ontogeny, Phylotypic Periods, Paedomorphosis, and Ontogenetic Systematics

The key terms linking ontogeny and evolution are briefly reviewed. It is shown that their application and usage in the modern biology are often inconsistent and incorrectly understood even within the “evo-devo” field. For instance, the core modern reformulation that ontogeny not merely recapitulates, but produces phylogeny implies that ontogeny and phylogeny are closely interconnected. However, the vast modern phylogenetic and taxonomic fields largely omit ontogeny as a central concept. Instead, the common “clade-” and “tree-thinking” prevail, despite on the all achievements of the evo-devo. This is because the main conceptual basis of the modern biology is fundamentally ontogeny-free. In another words, in the Haeckel’s pair of “ontogeny and phylogeny,” ontogeny is still just a subsidiary for the evolutionary process (and hence, phylogeny), instead as in reality, its main driving force. The phylotypic periods is another important term of the evo-devo and represent a modern reformulation of Haeckel’s recapitulations and biogenetic law. However, surprisingly, this one of the most important biological evidence, based on the natural ontogenetic grounds, in the phylogenetic field that can be alleged as a “non-evolutionary concept.” All these observations clearly imply that a major revision of the main terms which are associated with the “ontogeny and phylogeny/evolution” field is urgently necessarily. Thus, “ontogenetic” is not just an endless addition to the term “systematics,” but instead a crucial term, without it neither systematics, nor biology have sense. To consistently employ the modern ontogenetic and epigenetic achievements, the concept of ontogenetic systematics is hereby refined. Ontogenetic systematics is not merely a “research program” but a key biological discipline which consistently links the enormous biological diversity with underlying fundamental process of ontogeny at both molecular and morphological levels. The paedomorphosis is another widespread ontogenetic-and-evolutionary process that is significantly underestimated or misinterpreted by the current phylogenetics and taxonomy. The term paedomorphosis is refined, as initially proposed to link ontogeny with evolution, whereas “neoteny” and “progenesis” are originally specific, narrow terms without evolutionary context, and should not be used as synonyms of paedomorphosis. Examples of application of the principles of ontogenetic systematics represented by such disparate animal groups as nudibranch molluscs and ophiuroid echinoderms clearly demonstrate that perseverance of the phylotypic periods is based not only on the classic examples in vertebrates, but it is a universal phenomenon in all organisms, including disparate animal phyla.

The First Brazilian Thesis of Evolution: Haeckel's Recapitulation Theory and Its Relations with the Idea of Progress

The aim of this work is to present the thesis "On the Ontogenetic Evolution of the Human Embryo in its Relations with Phylogenesis," by Affonso Regulo de Oliveira Fausto (1866-1930), published in Brazil in 1890. To our knowledge, it was one of the first Brazilian academic works focused specifically on evolution. It was also the first doctoral thesis that addressed the topic of recapitulation in order to analyze what was then called the progressive evolution of the human species in tandem with the embryological development of the individuals that would constitute the Brazilian "type." In the present work, we analyze the author's thesis in relation to its sources, concepts, as well as the country's political context at the time of its publication. Fausto's text, in which he explicitly recognized the influence of Ernst Haeckel's (1834-1919) recapitulation theory, represents a window to understand better a concept of nation based on science and on the idea of inexorable progress that was accepted in Brazil at the end of the nineteenth century.

On the historical roots of creationism and intelligent design: German Allmacht and Darwinian evolution in context

As detailed in a Letter published in Science in 2017, the adherents of creationism and intelligent design are still active in promoting their biblical-literalist views of the origin and evolution of life on Earth. In this contribution, we take a look at this ideological phenomenon in the USA and analyze the philosophical roots of this ongoing movement. Specifically, we discuss Vernon Kellogg's book entitled Headquarters Nights (1917) with reference to the German 'Allmacht' (English-omnipotence) and Darwinian evolution to demonstrate how this publication bolstered the development of active anti-evolutionism in the USA among American fundamentalist Christians, inclusive of the Intelligent Design (ID)-agenda. The current activities of creationist associations in the USA and Germany are summarized, with reference to a new pro-ID-group established in Austria in 2019 that is sponsored by the Discovery Institute in Seattle, Washington (USA).

Archaeal Origins of Eukaryotic Cell and Nucleus

Symbiosis is a major evolutionary force, especially at the cellular level. Here we discuss several older and new discoveries suggesting that besides mitochondria and plastids, eukaryotic nuclei also have symbiotic origins. We propose an archaea-archaea scenario for the evolutionary origin of the eukaryotic cells. We suggest that two ancient archaea-like cells, one based on the actin cytoskeleton and another one based on the tubulin-centrin cytoskeleton, merged together to form the first nucleated eukaryotic cell. This archaeal endosymbiotic origin of eukaryotic cells and their nuclei explains several features of eukaryotic cells which are incompatible with the currently preferred autogenous scenarios of eukaryogenesis.

A Place for Viruses on the Tree of Life

Viruses are ubiquitous. They infect almost every species and are probably the most abundant biological entities on the planet, yet they are excluded from the Tree of Life (ToL). However, there can be no doubt that viruses play a significant role in evolution, the force that facilitates all life on Earth. Conceptually, viruses are regarded by many as non-living entities that hijack living cells in order to propagate. A strict separation between living and non-living entities places viruses far from the ToL, but this may be theoretically unsound. Advances in sequencing technology and comparative genomics have expanded our understanding of the evolutionary relationships between viruses and cellular organisms. Genomic and metagenomic data have revealed that co-evolution between viral and cellular genomes involves frequent horizontal gene transfer and the occasional co-option of novel functions over evolutionary time. From the giant, ameba-infecting marine viruses to the tiny Porcine circovirus harboring only two genes, viruses and their cellular hosts are ecologically and evolutionarily intertwined. When deciding how, if, and where viruses should be placed on the ToL, we should remember that the Tree functions best as a model of biological evolution on Earth, and it is important that models themselves evolve with our increasing understanding of biological systems.

How can recapitulation be reconciled with modern concepts of evolution?

To understand Haeckel's idea of recapitulation with modern evolutionary biology, one has to realize how evolutionarily conserved embryonic stages appear sequentially in developmental processes as chains of causality. Whether the idea of evolution was accepted or not, Haeckel and von Baer commonly saw an importance of a particularly conserved mid-embryonic stage in biphasic development of metazoans, the phylotype, that defines an animal phylum as the developmental source of a basic body plan. In an evolutionary context, the phylotypic stage was once understood by Haeckel to reflect the common ancestor of animal phyla, which went through hypermorphosis independently into various phyla. Recent comprehensive molecular studies, however, accumulated data to refute this idea. The conserved embryonic pattern does not reflect an ancestral adult morphology but appears to have arisen primarily as an embodiment of developmental constraints established through evolutionary processes. How the developmental burden results in a nested series of constraints will solve the recapitulative tendency of developmental programs.

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.