Haeckel's 1866 tree of life and the origin of eukaryotes

What Whole Genome Sequencing Has Told Us About Pathogenic Vibrios

When the first microbial genome sequences were published just 20 years ago, our understanding regarding the microbial world changed dramatically. The genomes of the first pathogenic vibrios sequenced, including Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus revealed a functional and phylogenetic diversity previously unimagined as well as a genome structure indelibly shaped by horizontal gene transfer. The initial glimpses into these organisms also revealed a genomic plasticity that allowed these bacteria to thrive in challenging and varied aquatic and marine environments, but critically also a suite of pathogenicity attributes. In this review we outline how our understanding of vibrios has changed over the last two decades with the advent of genomics and advances in bioinformatic and data analysis techniques, it has become possible to provide a more cohesive understanding regarding these bacteria: how these pathogens have evolved and emerged from environmental sources, their evolutionary routes through time and space, how they interact with other bacteria and the human host, as well as initiate disease. We outline novel approaches to the use of whole genome sequencing for this important group of bacteria and how new sequencing technologies may be applied to study these organisms in future studies.

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.

Ernst Haeckel, ancient forests, and the Anthropocene

In this Addendum to an article in  Nature commemorating the 100th anniversary of Ernst Haeckel's death (9 August 1919), we recall the largely forgotten fact that Haeckel (1868) was an early proponent of the concept of an "Anthropozoic Age", a 19th-century anticipation of the "Anthropocene". Haeckel in particular highlighted man's extensive remodeling of the planet in ancient forests. Earlier influences on Haeckel included Alexander von Humboldt (1769-1859) and dozens of similar writers in the 19th century Romantic era, including the Italian geologist and priest Antonio Stoppani (1824-1891), and the American diplomat and environmentalist George P. Marsh (1801-1882). Starting in the 1840s, Marsh described in extraordinary detail the destructive influence of mankind on natural ecosystems, again with particular emphasis on the destruction of forests. Marsh, like Haeckel after him, was a pioneer in describing the far-reaching human re-modeling of the planet that they and their colleagues presciently labeled the "Anthropozoic Age".

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.

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.

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.

Plasmodial slime molds and the evolution of microbial husbandry

Detailed analyses into the life cycle of the soil-dwelling microbe Dictyostelium discoideum led to the conclusion that this "social amoeba" practices some form of "non-monoculture farming" via the transfer of bacteria to novel environments. Herein, we show that in myxomycetes (plasmodial slime molds or myxogastrids) a similar "farming symbiosis" has evolved. Based on laboratory studies of two representative species in the genera Fuligo and Didymium, the sexual life cycle of these enigmatic microbes that feed on bacteria was reconstructed, with reference to plasmo- and karyogamy. We document that the spores carry and transfer bacteria and hence may inoculate new habitats. The significance of this finding with respect to Ernst Haeckel's work on myxomycetes and his concept of ecology are addressed.

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.

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.