Ernst Haeckel (1834-1919)

"I established the opposite view, that this history of the embryo (ontogeny) must be completed by a second, equally valuable, and closely connected branch of thought - the history of race (phylogeny). Both of these branches of evolutionary science, are, in my opinion, in the closest causal connection; this arises from the reciprocal action of the laws of heredity and adaptation... 'ontogenesis is a brief and rapid recapitulation of phylogenesis, determined by the physiological functions of heredity (generation) and adaptation (maintenance).'"
Haeckel, E. 1899. Riddle of the Universe at the Close of the Nineteenth Century.

Biography of Haeckel

Ernst Haeckel, much like Herbert Spencer, was always quotable, even when wrong. Although best known for the famous statement "ontogeny recapitulates phylogeny", he also coined many words commonly used by biologists today, such as phylum, phylogeny, and ecology. On the other hand, Haeckel also stated that "politics is applied biology", a quote used by Nazi propagandists. The Nazi party, rather unfortunately, used not only Haeckel's quotes, but also Haeckel's justifications for racism, nationalism and social darwinism.

Although trained as a physician, Haeckel abandoned his practice in 1859 after reading Darwin's Origin of Species. Always suspicious of teleological and mystical explanation, Haeckel used the Origin as ammunition both to attack entrenched religious dogma and to build his own unique world view.

Hackel studied under Carl Gegenbauer in Jena for three years before becoming a professor of comparative anatomy in 1862. Between 1859 and 1866, he worked on many "invertebrate" groups, including radiolarians, poriferans (sponges) and annelids (segmented worms). He named nearly 150 new species of radiolarians during a trip to the Mediterranean. "Invertebrates" provided the fodder for most of his experimental work on development, leading to his "law of recapitulation". Haeckel was also a free-thinker who went beyond biology, dabbling in anthropology, psychology, and cosmology. Haeckel's speculative ideas and possible fudging of data, plus lack of empirical support for many of his ideas, tarnished his scientific credentials. However, he remained an immensely popular figure in Germany and was considered a hero by his countrymen.

Haeckel's Scientific Thought

While materialists and utilitarians were shaking away traditional beliefs in England, German thinking was decidely more idealist and romantic during the eighteenth and nineteenth centuries. The influential philosopher Goethe, who like Haeckel lived for a time in Jena, stressed the importance of the spirit as a creative, organizing force. German morphologists, influenced both by Goethe and by Hegel's idealistic philosophy, believed in progressive perfection of both the universal plan of creation and the recapituation of that plan in the growth of the embryo.

Haeckel was influenced both by the German idealistic tradition and by the works of Darwin. After reading Origin of Species, Haeckel became one of the more prolific and vociferous supporters of evolution, but was less supportive of natural selection as the mechanism by which evolution occured. Hacekel was certainly an evolutionist but less so a Darwinian.

An extremely common misperception is that natural selection and evolution are the same thing. In fact, Haeckel is one of many thinkers who believed that all species were historical entities (lineages) but did not share Darwin's enthusiasm for natural selection as the main mechanism for generating the diversity of the biological world. Haeckel instead believed that the environment acted directly on organisms, producing new races (a version of Lamarckism). The survival of the races did depend on their interaction with the environment, a weak form of natural selection. Haeckel's mechanism of change required that formation of new characters diagnostic of new species occured through progressive addition to the developmental trajectory. For example, most metazoans go through a developmental stage called a gastrula -- a ball of cells with an infolding that later forms the gut. Haeckel thought that at one time an organism called a "gastraea" existed that looked much like the gastrula stage of ontogeny. This hypothesized ancestral metazoan gave rise to the rest of the multi-celled animals.

The "law of recapitulation" has been discredited since the beginning of the twentieth century. Experimental morphologists and biologists have shown that there is not a one-to-one correspondence between phylogeny and ontogeny. Although a strong form of recapitulation is not correct, phylogeny and ontogeny are intertwined, and many biologists are beginning to both explore and understand the basis for this connection.