Subject: biography, biology
German zoologist well known for his genealogical trees of living organisms and for his early support of Darwin's ideas on evolution.
Haeckel was born in Potsdam, Prussia (now in Germany), on 16 February 1834. His father was a lawyer in Merseburg, where Ernst Haeckel was educated. He studied medicine (although his main interest was botany) at the University of Würzburg and obtained his degree from the University of Berlin in 1857. There he was taught by Johannes Müller (1801-1858), who interested him greatly in zoology; he also studied under Rudolf Virchow (1821-1902). Haeckel travelled through Italy and then, after practising medicine for a year, became a lecturer at the University of Jena in 1861. The following year he was appointed extraordinary professor of comparative anatomy at the Zoological Institute in Jena. He founded the Phyletic Museum in Jena and the Ernst Haeckel Haus, which contains his archives as well as many personal mementos. In 1865 he took up the full professorship at Jena, a position he retained until he retired in 1909. He died in Jena on 8 August 1919.
In 1866 Haeckel met Charles Darwin and was completely convinced by his theory of evolution. He went further and, using Darwin's research, developed Haeckel's law of recapitulation, which concerns resemblances between the ontogeny (the development from fertilized egg to adult) of different animals. According to the law of recapitulation, during its ontogeny an individual goes through a series of stages similar to the evolutionary stages of its adult ancestors, which show characteristics of less highly evolved animals. In this way ontogeny recapitulates phylogeny (the developmental history of a species). An example of the evidence on which Haeckel founded this view is the series of gill pouches found both in birds and mammals at the embryo stage. These gill pouches are not present in adult mammals, although the slits are present in full-grown birds and fish from which the embryo forms were descended. Haeckel's theory was thought to make ontogeny relevant to evolution simply because he believed that it should be possible to find out, by studying the development of an individual, what its adult ancestors were like. The concept that Haeckel revived had already been refuted by Karl von Baer, who had shown that embryos resemble the embryos only and not the adults of other species, but Haeckel's claims remained popular to the end of the 19th century.
In the same year that he met Darwin, Haeckel introduced a method of representing evolutionary history, or phylogeny, by means of tree-like diagrams. His method is still used today by animal systematists to show degrees of presumed relationship in the various groups and can be traced in present modified zoological classifications.
Haeckel also tried to apply Darwin's doctrine of evolution to philosophy and religion. He believed that just as the higher animals have evolved from the simpler forms of life, so the highest human faculties have evolved from the soul of animals. He denied the immortality of the soul, the freedom of the will, and the existence of a personal God. He now occupies no serious place in the history of philosophy, although he was widely read in his own day.
Haeckel held some ideas that are still accepted, one of them being his view that the origin of life lies in the chemical and physical factors of the environment, such as sunlight, oxygen, water, and methane. This theory has recently, as a result of laboratory experiments, been shown to be likely. He also believed that the simplest forms of life were developed by a form of crystallization. A further influence Haeckel had on science was the coining of the word ‘ecology’, to mean the study of living organisms in relation to one another and to the inanimate environment. As a field naturalist Haeckel was a man of extraordinary energy, and he gave much of interest to biology, even if the theory was tenuous and was typical of the extreme evolutionists of his era.
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