Étienne Geoffroy Saint-Hilaire bigraphy, stories - Naturalist

Étienne Geoffroy Saint-Hilaire : biography

15 April 1772 - 19 June 1844

Étienne Geoffroy Saint-Hilaire (15 April 1772 – 19 June 1844) was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories. Geoffroy's scientific views had a transcendental flavor (unlike Lamarck's materialistic views) and were similar to those of German morphologists like Lorenz Oken. He believed in the underlying unity of organismal design, and the possibility of the transmutation of species in time, amassing evidence for his claims through research in comparative anatomy, paleontology, and embryology.

Geoffroy's theory

Geoffroy was a deist, which is to say that he believed in a God, but also in a law-like universe, with no supernatural interference in the details of existence. This kind of opinion was common in the Enlightenment, and goes with a rejection of revelation and miracles, and does not interpret the Bible as the literal word of God. These views did not conflict with his naturalistic ideas about organic change.

Geoffroy's theory was not a theory of common descent, but a working-out of existing potential in a given type. For him, the environment causes a direct induction of organic change. This opinion Ernst Mayr labels as 'Geoffroyism'.Ernst Mayr (1982). The Growth of Biological Thought: Diversity, Evolution and Inheritance. Harvard. p. 262 It is definitely not what Lamarck believed (for Lamarck, a change in habits is what changes the animal). The direct effect of environment is not believed today by any main-stream evolutionist; even Lawrence knew by 1816 that the climate does not directly cause the differences between human races.

Geoffroy endorsed a theory of saltational evolution that "monstrosities could become the founding fathers (or mothers) of new species by instantaneous transition from one form to the next."Benedikt Hallgrímsson, Brian K. Hall. (2011). Variation: A Central Concept in Biology. Academic Press. p. 18 In 1831 he speculated that birds could have arisen from reptiles by an epigenetic saltation.Brian K. Hall, Roy D. Pearson. (2004). Environment, Development, and Evolution: Toward a Synthesis. A Bradford Book. p. 9 Geoffroy wrote that environmental pressures could produce sudden transformations to establish new species instantaneously.Peter J. Bowler. (2003). Evolution: The History of an Idea. University of California Press. p. 127 In 1864 Albert von Kölliker revived Geoffroy's theory that evolution proceeds by large steps, under the name of heterogenesis.Sewall Wright. (1984). Evolution and the Genetics of Populations: Genetics and Biometric Foundations Volume 1. University of Chicago Press. p. 10

Later career

In 1809, the year after his return to France, Geoffroy was made professor of zoology at the faculty of sciences at Paris, and from that period he devoted himself more exclusively than before to anatomical study. In 1818 he published the first part of his celebrated Philosophie anatomique, the second volume of which, published in 1822, and subsequent memoirs account for the formation of monstrosities on the principle of arrest of development, and of the attraction of similar parts.

Geoffroy's friend Robert Edmund Grant shared his views on unity of plan and corresponded with him while working on marine invertebrates in the late 1820s in Edinburgh (assisted in 1826 and 1827 by his student Charles Darwin) when Grant successfully identified the pancreas in molluscs. When, in 1830, Geoffroy proceeded to apply to the invertebrata his views as to the unity of animal composition, he found a vigorous opponent in Cuvier, his former friend.

Geoffroy, a synthesiser, contended, in accordance with his theory of unity of plan in organic composition, that all animals are formed of the same elements, in the same number; and with the same connections: homologous parts, however they differ in form and size, must remain associated in the same invariable order. With Johann Wolfgang von Goethe he held that there is in nature a law of compensation or balancing of growth, so that if one organ take on an excess of development, it is at the expense of some other part; and he maintained that, since nature takes no sudden leaps, even organs which are superfluous in any given species, if they have played an important part in other species of the same family, are retained as rudiments, which testify to the permanence of the general plan of creation. It was his conviction that, owing to the conditions of life, the same forms had not been perpetuated since the origin of all things, although it was not his belief that existing species are becoming modified.

Living octopus

Living octopus

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