The German biologist and natural philosopher Ernst Heinrich Philipp August Haeckel (1834-1919) was famous for his work in evolutionary theory, especially the construction of phylogenetic trees. In the late 19th and early 20th centuries he was as famous as Charles Darwin, whom he admired, though his views were closer to those of Jean Baptiste Lamarck.

Ernst Haeckel was born in Potsdam, Germany, on February 16, 1834, to Carl and Charlotte (Sethe) Haeckel. His father was the chief administrator for religious and educational affairs in Merseburg, while his mother was the daughter of a privy councillor in Berlin. Haeckel thus had the social advantage of growing up in an educated and cultured family. He was publicly educated at the Domgymnasium in Merseburg, graduating in 1852. He then, on the advice of his parents, studied medicine at Berlin, later at Würzburg and Vienna, before returning to Berlin to earn his medical degree in 1857.

In 1858 he passed the state medical examination, but he did not practice medicine. In fact, he had never been truly interested in being a physician, only pursuing that degree for his parents' sake. Yet he discovered, after initial reluctance, that medical school would provide him with the most solid foundation on which to build a scientific career. It was in this medical training that Haeckel met many of the most important biologists of his day. At Würzburg he studied under Albert von Kölliker and Franz Leydig, learning embryological and comparative anatomy as well as perfecting his skills in microscopical investigations--later to prove essential for his research in ontogeny and phylogeny.

It was also at Würzburg that Haeckel's philosophical views began to develop, confronted as he was by mechanistic and materialistic views of life developed by Rudolf Virchow and Carl Vogt and expressed by young scientists and physicians with whom he came into contact. In response to such strongly asserted materialism Haeckel's own Christian beliefs began to be transformed, and though he never relinquished the idea of god, his own god was eventually so radically changed that it seemed scarcely personal, perhaps nothing more than the principle of causality in the universe. Meanwhile, his medical education continued. At Berlin in 1854-1855 Haeckel studied under Johannes Müller, whom he greatly respected as the paradigm of the great scientist. Under Müller, he increased his understanding of comparative anatomy and he was introduced to marine zoology, one of Müller's specialties.

In 1858, after finishing his medical studies and final examination, Karl Gegenbaur offered him the chance of a future professorship in zoology at Jena if he would first undertake a zoological research expedition in the Mediterranean. This research occupied his time from 1859 to 1860 and resulted in the publication in 1862 of The Radiolarians, in which he announced his support of Darwinism. Haeckel determined to reinterpret all of morphology (study and comparison of animal forms) in terms of the theory of evolution, which meant the linking of animal species phylogenetically through "geneological" trees. He argued that all processes could be reduced to mechanical-materialistic causes, that evolution was driven by such causality, and that the true philosophy of nature should be Monism, a system stressing the unity of mind and matter, in contrast to all vitalistic or teleological dualism stressing the separation of mind and matter. He differed from Darwin in two fundamental ways--Haeckel's was the more speculative mind, and he relied much more upon the Lamarckian principle of the inheritance of acquired characteristics than Darwin ever did.

Also in 1862, Haeckel married his cousin, Anna Sethe, who died in 1864, at which time he married Agnes Huschke, daughter of anatomist Emil Huschke. They had three children. In 1861, upon his return from his research expedition, Haeckel had been given the post of Privatdozent at the University of Jena. In 1862 he was named professor extraordinary in comparative anatomy and was made director of the Zoological Institute. And in 1865 a chair in zoology was established for him, which he held until 1909. During that more than 40 year period Haeckel continued his herculean labors on behalf of his science, going on four major scientific expeditions (Canary Islands, 1866-1867; Red Sea, 1873; Ceylon, 1881-1882; Java, 1900-1901) and further elaborating on his evolutionary schemes.

In 1901 he was the recipient of the Turin Bressa Prize for his outstanding work in biology. Throughout his life he received many honors and was elected to many scientific societies, among them the Imperial Academy of Sciences at Vienna (1872), the American Philosophical Society (1885), and the Royal Society of Edinburgh (1888). His most characteristic ideas and tendencies are evident in his early work of 1886, General Morphology--all his subsequent efforts were reworkings of this book. He retired in 1909 and still lived in Jena when he died in 1919.

Further Reading

• For a short but excellent intellectual and biographical sketch of Haeckel, see Georg Uschmann's article in the Dictionary of Scientific Biography, Volume 6. E. W. MacBride also wrote a short article in Nature 133 (1934) on the centenary of Haeckel's birth. Daniel Gasman in his Scientific Origins of National Socialism (1971) explored the way in which the Nazi's used Haeckel's ideas to support their own political ideology. For Haeckel's personal evolutionary views, see his General Morphology (1866).