LAMARCK, JEAN BAPTISTE PIERRE ANTOINE DE MONET DE (b. Bazentin-le-Petit, Picardy, France, 1 August 1744; d. Paris, France, 28 December 1829), botany, invertebrate zoology and paleontology, evolution.

    analogues. There were some people at the museum, however, who were discovering analogues. Alexandre Brongniart and, slightly later, Faujas de Saint-Fond and Étienne Geoffroy Saint-Hilaire were investigating similarities between some fossil and living reptiles.

Several naturalists, including Faujas, expected Lamarck's investigations of shells from living and fossil forms to resolve the issue. His work did reveal a number of analogues. The question then became one of explaining the similarities and differences. Although the existence of analogues would rule out the possibility of a general catastrophe, more limited violent events could have produced some species extinction which would account for the failure to find analogues in many cases. There were, Burkhardt suggests, two other ways to explain the differences: migration or evolution. Lamarck, unable for philosophical reasons to entertain the possibility of extinction and unconvinced of migration as a plausible way to account for all the differences, chose an evolutionary explanation sometime in late 1799 or early 1800. Differences between living and fossil forms existed precisely because organisms had undergone change over time; Lamarck regarded this position as one of the strongest arguments against extinction. The study of fossil forms led Lamarck to conceive of nature as existing in time. Lamarck has often been called the founder of invertebrate paleontology. His most important work on the subject was Mémoires sur les fossiles des environs de Paris (1802-1806). The “Introduction” to this work discusses the significance of fossils for a theory of the earth.

Geology.

Lamarck's geology was closely connected with his work in other fields. His Hydrogéologie, which grew out of a 1799 memoir presented to the Academy and his work in invertebrate paleontology, was published in 1802. He originally intended it to be a much broader work, as the manuscript shows (Muséum National d'Histoire Naturelle, Paris, MS 756-1, 2). It was to have been a terrestrial physics including meteorology, geology, and biology, a term he coined. He had not only a sense of the interrelation of fields but, within geology, a vision of the whole. He saw all of nature working according to similar principles: general natural tendencies producing gradual change over long periods of time, with local circumstances explaining the irregularities. His approach to geology was similar to that in other sciences: concern with the general principles and contempt for those who interested themselves too much with the specifics.

Although Lamarck's geological views were not original (he was strongly influenced by Buffon and Daubenton, among others), they were an important part of his conception of nature. His preoccupation with marine fossil shells had a decisive influence on his choice of geological theories. Since such shells had to have been laid down in water, he needed a theory to explain how this was possible. As in his meteorology, he used the moon as the main cause, in this case of a constant slow progression of the oceans around the globe. The main geological force was water acting according to uniformitarian principles over millions of years. The substances of the mineral kingdom were produced by the progressive disintegration of organic remains; water operated on these products to produce geological formations such as mountains. Lamarck's uniformitarianism and great geological time scale have led some to say that he was his own Lyell. Some historians have thought that Lamarck's perception of a slowly changing environment and the resulting necessity of organisms to change or become extinct (a possibility he could not accept) led him to his theory of evolution.

Theory of Evolution.

Before beginning a discussion of Lamarck's theory of evolution, it is important to point out that he never used the term “evolution” but, rather, spoke of the path or order which nature had followed in producing all living organisms. “Evolution” is used here only as a shorthand form for Lamarck's longer phrases.

Lamarck's first public presentation of his theory of evolution was in his opening discourse for his course on invertebrates at the museum in 1800; it was published the following year at the beginning of his Système des animaux sans vertèbres. The evolutionary views sketched in the discourse leave much to be desired in terms of organization and explanation. They are, however, very much a part of a total view of nature, many aspects of which Lamarck had long accepted. Natural products consisted of living and nonliving things; in the two branches of living organisms, Lamarck pointed out the “degradations” in structural organization of the larger classificatory groupings or “masses” as one moved down the series from the most complex to the simplest. He indicated his lack of clarity about the new views he was proposing by using the term “complication” interchangeably with “degradation.” Nature, after having formed the simplest animals and plants directly, produced all others from them with the aid of time and circumstances. In 1800 Lamarck did not explain how spontaneous generation occurred or how unlimited time and varied circumstances produced all other organisms. He did suggest that, for animals, changing circumstances and physical needs led to new responses which eventually produced new habits; these habits tended to strengthen certain parts or organs through use.