In Zoological Philosophy, Jean-Baptiste Lamarck proposed a pre-Darwinian theory of organic evolution, or transmutation of species, and explained it by the twofold mechanism of natural progress and the inheritance of acquired characteristics.
The eighteenth century saw a number of naturalists, including the great taxonomist Carolus Linnaeus and, in later life, naturalist Georges Leclerc, comte de Buffon, question the immutability of species. According to the time period’s common understanding, any new forms resulted from either hybridization or degeneration of type. The idea of unlimited change found expression in the works of
Before 1800, Lamarck himself accepted the immutability of species, though his attempts to discover a natural classification of plants in his first book, published in 1779, became important when he later conceived of the evolutionary process. During the 1790’s, he worked on the classification of invertebrates, which had all been lumped together into one group. He also did research on physicochemical problems and attempted to convince his contemporaries that his chemistry was superior to the new chemistry of Antoine-Laurent Lavoisier.
Before publishing Philosophie zoologique: Ou, Exposition des considérations relative à l’histoire naturelle des animaux (1809; Zoological Philosophy: An Exposition with Regard to the Natural History of Animals, 1914), Lamarck had explored the principles of organic change, described in his Recherches sur l’organisation des corps vivans (1802; studies on the organization of living bodies). The principles include spontaneous generation at the lowest levels of the plant and animal kingdoms, the natural production of increasingly complex organisms from simpler ones, and the influence of the environment, which altered the natural progress toward ever-increasing complexity.
Two issues led Lamarck to the idea of the mutability of species. First was his rejection of the extinction of species, a phenomenon that had been suspected but not convincingly demonstrated until the 1790’s. As an adherent of geological uniformitarianism, the idea that geological changes were slow and steady, he rejected the explanation proposed by Georges Cuvier and others that geological catastrophes had erased entire species. Lamarck asserted that the forms no longer in existence had changed into present forms.
Second, Lamarck devised a theory of spontaneous generation to account for the origins of the simplest living forms. The causes of spontaneous generation were entirely physical: Light, combined with certain elements—for example, caloric and electric—occasioned the organization of inorganic matter and excited the process of life. Lamarck’s experience in classification supported his idea that nature progressed from simple to complex in the production of living beings. His theory of evolution rested on a phylogenetic
The fact of organic transformation required a cause. During the eighteenth century the idea of the march of human history had developed, that is, a natural course of progress, which circumstances modified. Along similar lines, Lamarck proposed two quite different causes for organic diversity. The first and more important cause was the tendency of nature to cause an increase in the complexity of organization of animals. The second cause was the influence of the environment upon heredity.
In chapter 7 of Zoological Philosophy, Lamarck elucidates the two laws of inheritance: first, continuous use strengthens an organ and continuous disuse weakens it until it ultimately disappears; second, through long-term environmental influences organisms developed needs that occasioned inherited changes in organs through use or disuse. These laws formed his principle of the inheritance of acquired characteristics.
Lamarck was inconsistent in his assertions concerning the necessity of both causes. In some places he argued that evolution occurred even in the absence of environmental effects; in others, having noted that when species reproduce in an unchanging environment they do not change, he seemed to deny the inevitability of progress. Lamarck provided three pages of speculations concerning how structures might change. For example, the membranes between the toes of a bird stretched until the webbed foot formed in waterfowl. The horns and antlers of male ruminants formed in response to the excess flow of inner fluids stirred up by fits of anger.
Lamarck had worked out these views by 1802 but published them seven years later in Zoological Philosophy, which contains three parts. Part 1 presents his views on the natural classification of animals, and that classification reveals increasing complexity, which is interrupted by environmental factors leading to the inheritance of acquired characteristics. Part 2 details Lamarck’s materialistic definition of life and his views on spontaneous generation. Part 3 encompasses his views on the nature of the nervous system, again explained in terms of physical causes. One of the functions of the nervous system was to create unconscious needs or instincts, the actions of which could change habits and lead to deviations from the progressive plan of nature.
Instincts are not universal in all species. Lamarck believed that the most important features of animals were the nervous, respiratory, and circulatory systems, in that order. On the linear scale of organisms, descending from the top position, occupied by humans, to the lowest, the infusoria, one could observe the simplification and finally the disappearance of these systems. In species with little-developed nervous systems in particular (and in plants), habits formed from the direct influence of the external fluids upon the internal organization, while in more advanced organisms, the nonconscious “internal sentiment” mediated the influence of the external fluids.
Lamarck’s ideas gathered a few adherents. However, even before the publication of Zoological Philosophy, Georges Cuvier, the most important comparative anatomist and paleontologist in France at the time, attacked Lamarck’s system. He rejected Lamarck’s geological uniformitarianism and organic transformationism and interpreted geological history as a series of alternations of catastrophes that caused extinction and creations of new species. Furthermore, he believed in a very tight or rigid organization of the organism, in which all structures worked together to perform the functions necessary to life. Any change in structure beyond the normal bounds would result in death. When Zoological Philosophy appeared, the general public as well as the scientific community largely ignored it.
Lamarck’s work represents one of the earliest attempts to explore species inheritance, the mutability of species, and organic evolution. Several years earlier, in the 1790’s, Erasmus Darwin
During the 1820’s several minor figures and a more important one, Jean-Baptiste Bory de Saint-Vincent
Charles Darwin
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Bowler, Peter J. Evolution, The History of an Idea. Rev. ed. Berkeley: University of California Press, 1989. Lengthy work examining theories of earth history and evolution from the sixteenth to the twentieth centuries. Highly useful for placing the work of Lamarck in its larger context. -
Burkhardt, Richard W., Jr. The Spirit of System: Now with “Lamarck in 1995.” Cambridge, Mass.: Harvard University Press, 1995. A reprint of Burkhardt’s authoritative 1977 book, along with a lengthy introductory essay assessing scholarship since its original publication. -
Corsi, Pietro. The Age of Lamarck: Evolutionary Theories in France, 1790-1830. Berkeley: University of California Press, 1988. A study focusing on Lamarck’s earlier scientific study of the organization of living bodies (1802), which contained most of his ideas on transmutation, and the reaction to his evolutionary theory by Cuvier and others. -
Gould, Stephen Jay. “A Division of Worms.” Natural History 108, no. 1 (February, 1999). Argues that Lamarck’s theory has been misread and that he modified his ideas during his studies after the publication of Zoological Philosophy. -
Lamarck, Jean-Baptiste. Lamarck’s Open Mind: The Lectures. Gold Beach, Oreg.: High Sierra Books, 2004. A reissue of six lectures given by Lamarck, including two relating to his theory of transmutation. -
_______. Zoological Philosophy: An Exposition with Regard to the Natural History of Animals. Translated by Hugh Elliot. Chicago: University of Chicago Press, 1984. The introductory essays by David L. Hull and Richard W. Burkhardt, Jr., provide an overview of the development and impact of Lamarck’s thought.
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Louis Agassiz; Karl Ernst von Baer; Samuel Butler; Georges Cuvier; Charles Darwin; Asa Gray; Ernst Haeckel; Thomas Henry Huxley; Sir Charles Lyell; Herbert Spencer.