Bronn, Heinrich Georg

(b. Ziegelhausen bei Heidelberg, Germany, 3 March 1800; d. Heidelberg, Germany, 5 July 1862)

paleontology, zoology.

Fundamental systematic works in paleontology are Bronn’s most enduring contribution to science. He was educated in public administration and natural science in Heidelberg, after which he traveled through northern Italy and southern France, making paleontological investigations. In 1833 he became professor of natural science at Heidelberg. For a short time Louis Agassiz studied with Bronn, and decades later returned to purchase Bronn’s collection of fossils for the newly established Museum of Comparative Zoology at Harvard.

In 1831 Bronn’s Italiens Tertiär-Gebilde distinguished different series of Tertiary strata on the principle that in successively more recent strata the number of extinct species diminishes while the number of modern species increases. His divisions correspond closely to those established as Eocene, Miocene, Older Pliocene, and Newer Pliocene in Lyell’s Principles of Geology (1833). Bronn’s extensive Lethaea geognostica, which sought to establish a chronological sequence of fossil organisms, summarized all that was then known in stratigraphy and paleontology. His later Index palaeontologicus and the Lethaea geognostica were for decades the chief reference works in paleontology. At his death Bronn left unfinished the enormous undertaking of systematizing the whole animal kingdom, recent as well as fossil forms, in Die Klassen und Ordnungen des Thier-reichs. From 1830 he edited the Jahrbuch für Mineralogie, Geognosie, Geologie, und Petrefackten-kunde with Karl von Leonhard, and later with Georg von Leonhard. Soon after Darwin’s Origin of Species appeared in 1859, Bronn, at Darwin’s suggestion, was responsible for having it translated into German.

Near the end of his life Bronn synthesized developmental laws of nature from his extensive and detailed paleontological studies. He rejected theories of development like those of Lamarck and Geoffroy St. Hilaire and the modification of one species into another. Instead, he explained progressive development, “the successive appearance of forms with more and more complicated organization,” by a law of creation operating according to a definite plan. Species became extinct and were replaced by improved ones within the limits imposed by the external “conditions of existence.” Bronn used this phrase, borrowed from Cuvier, to indicate adaptation to environment rather than functional harmony, as Cuvier had. The conditions of existence, which exerted a negative, restricting effect on organic development, varied as the earth’s crust evolved. During the formation of the crust the primitive ocean was first modified by the appearance of islands and mountain chains, which then grew into continents, thereby dividing the earth’s surface into separate oceans, inland seas, lakes, coastal plains, and mountain ranges. The organic kingdoms adhered to a law of terripetal evolution analogous to the development of the crust. At first entirely pelagic, they evolved littoral, then coastal, and finally continental forms.

Bronn emphasized that these changes, both organic and inorganic, had been gradual and continuous. Like many of his contemporaries, he criticized the new glacial theory of Louis Agassiz because it appeared to introduce a catastrophe into the history of the world. Bronn argued that the gaps then acknowledged in the paleontological and stratigraphic succession were illusory and would be bridged by the future discovery of transitional species and intermediate formations. (Compare Darwin’s similar essay, “On the Imperfection of the Geological Record,” Origin of Species, ch. 9.)

Bronn’s contributions, both theoretical and systematic, were recognized by his contemporaries. In 1857 his “Laws of Evolution of the Organic World” won the prize of the Academy of Sciences of Paris. For the Handbuch einer Geschichte der Natur he was awarded a prize medal by the Scientific Society of Haarlem, and in 1861 he received the Wollaston Prize of the Geological Society of London.

BIBLIOGRAPHY

Bronn’s main theoretical contributions are found in his Untersuchungen über die Entwicklungsgeschichte der organischen Welt während der Bildungszeit unserer Erdoberfläche (Stuttgart, 1858), of which the last chapter, summarizing the whole work, is available in English in The Annals and Magazine of Natural History, 3rd ser., 4 (1859), 81–90, 175–184.

His more important classificatory and descriptive works are Gaea Heidelbergensis, oder Mineralogische Beschreibung der Gegend von Heidelberg (Heidelberg, 1830); Italiens Tertiär-Gebilde und deren organischen Einschlüsse (Heidelberg, 1831); Lethaea geognostica, oder Abbildungen und Beschreibungen der für die Gebirgs-Formationen bezeichnendsten Versteinerungen, 2 vols. (Stuttgart, 1835–1838 and several later editions); Handbuch einer Geschichte der Natur, 2 vols. (Stuttgart, 1841–1843), which includes as its third part Index palaeontologicus, a systematic reduction of all published lists of fossils; and Die Klassen und Ordnungen des Thier-reichs, wissenschaftlich dargestellt in Wort und Bild (begun in 1859 and continued after Bronn’s death), paleontology and zoology combined in one system.

For a list of his memoirs, see the Royal Society Catalogue of Scientific Papers, I, VII.

For biographical information, see the obituary notice in the Quarterly Journal of the Geological Society of London, 19 (1863), xxxii–xxxiii.

Bert Hansen