Ernst Haeckel (100 years)

This blog post is an abridged version. The full length article will be available in the September issue of PuLSe.

Opening up the Origin

During his own lifetime, and in the 100 years since his death, the great German naturalist and morphologist Ernst Haeckel (1834–1919) has been a controversial figure. Not only was he probably the greatest promulgator of Darwinian ideas in the world of the early 20th century, he conceived the underpinning of the phylogenetic paradigm with which we see all of life today, and was an accomplished artist whose drawings influenced the German artistic movement Jugenstil (Art Nouveau). His plates from Kunstformen der Natur (Art Forms in Nature) have also influenced contemporary artists and designers. He was commissioned to undertake the identification of the radiolarians for the famous British Challenger expedition in the 1870s—the first global natural history survey of ocean life—and described more than 4,000 species of these exquisite unicellular organisms. He went on to be awarded the Linnean Society’s Linnean Medal in 1894.

He was surrounded by controversy (see Richards’ The Tragic Sense of Life for details), but instead, I wish to emphasise that Haeckel was not only a pivotal figure in the acceptance of evolutionary thought, but also that he deserves merit for bringing art and science together.

Early days

Ernst Haeckel was born in 1834, to a family of lawyers in Potsdam, on the outskirts of Berlin. He was, as was common at the time, educated at home, imbibing German poetry from his mother, and a love of geology and travel from his father. He went on to attend medical school in Würzburg, whose star professor was Rudolf Virchow (1821–1902). Despite a revulsion for the practice of medicine, Haeckel continued with his studies, inspired by Virchow’s use of the microscope to study anatomy and morphology, but focused on natural history.

He became engaged to his long-term love, Anna Sethe, though without a job marriage was not possible. However an invitation to Italy changed this. The diversity of marine life in the seas around Messina, near Naples, led him to study the almost unknown radiolaria—a group of single-celled organisms (“zooplankton”) with silica skeletons. He not only described new species, but carefully analysed their internal structure, something never before achieved. It was during the preparation of the resulting monograph in the summer of 1860 that he buried himself in the German translation of Charles Darwin’s Origin of Species (that interestingly left out one of its final sentences: “Light will be thrown on the origins of man and his history”), and pieces clicked together.

Descent, death and radiolarians

Haeckel realised that his studies on radiolarians provided positive evidence for descent with modification—the central thesis of the Origin. His two-volume monograph published in 1862 (Die Radiolarien (Rhizopoda Radiaria): eine Monografie) was received to great acclaim, with Darwin himself pronouncing it one of the most magnificent scientific works he had ever seen. The monograph was instrumental in Haeckel’s obtaining a position at the University of Jena, allowing him to marry Anna. But both triumph and tragedy struck in 1864; on the same day Haeckel was informed he had been awarded the prestigious Cothenius Medal for his monograph, Anna died of pleurisy. His despair at losing Anna coloured the rest of his scientific life.

Missing links

Haeckel became the strongest proponent of Darwin’s ideas worldwide, and it is said that more people were exposed to evolutionary theory through Haeckel’s works than through the Origin itself. But his writing style did not endear him to critics and non-evolutionists. His anguish over Anna’s death led him to completely reject religion. His 1868 book Natürliche Schopfungsgeschichte (The Natural History of Creation) boldly asserted that descent with modification was the unifying basis for all diversity, including that of human beings and their languages. The diagrams depicted descent with modification as trees—most famously as a gnarled oak. He speculated that “missing links” would be found to connect apes with humans (in the late 1890s Eugène Dubois went on to discover fossils of Homo erectus). This too was rejected by Haeckel’s detractors; his old professor Rudolf Virchow, who had become what might be termed “anti-Haeckelian”, maintained the fossils were not human at all.

Controversy continued to dog Haeckel even in death. In order to better conform to his “ontology recapitulates phylogeny” argument (essentially that shared features of embryos are evidence of commonality of descent of all vertebrates), he had been accused of altering the supporting embryological diagrams. This charge was resurrected in the late 20th century, and has been used by anti-evolutionists espousing intelligent design as “proof” that Darwin was wrong, and that descent with modification is not how life evolves. His diagram of the relationships of the races of humans has been used to accuse his work of being the springboard behind National Socialism in Germany. The context of his work is perhaps deliberately misunderstood—these studies of relationships were commonplace at the time, and Haeckel never mentioned anything about racial “purity”. Haeckel’s works were even on Nazi lists of banned books—hardly an endorsement.

In truth, Haeckel was a careful scientist whose fierce defense of Darwinian theory did so much to cement its centrality in today’s biology. In addition, his artistic talent did much to subtly show a non-scientific public how organismal form provided the evidence for common descent, as well as being incredibly beautiful. Ernst Haeckel deserves to be remembered not just for his seminal contribution to today’s evolutionary biology, but also for his zeal in bringing the wonders of nature to audiences of all types.

By Dr Sandra Knapp, President, Linnean Society of London