Jean-Baptiste Pierre Antoine de Monet de Lamarck was born in Picardy, France, on August 1, 1744. He received a Jesuit education at Amiens and briefly pursued a military career before turning to science. Lamarck's interests ranged widely from natural history to meteorology, and with the reorganization of the Jardin du Roi into the Muséum d'Histoire Naturelle in 1793, he was appointed to the professorship of invertebrates. Lamarck's central concern, reflecting his Enlightenment values, was to present a thoroughly naturalistic and developmental account of all aspects of the natural world. His developmental geology followed uniformitarian principles, and his deism rendered irrelevant the optimism of natural theology and dissolved the distinction between humans and other animals. Lamarck believed that "life" is a force imposed on the universe by the creator, but he rejected any idea of a plan for the development of species. His early interest in botanical classification led to his conversion to a transformationist position after 1800, allowing him to explain a wide range of biological phenomena in one coherent system. Lamarck died in relative obscurity on December 18, 1829. His most influential works were his Hydrogéologie (1802), Recherches sur l'organisation des corps vivants (1802), Philosophie zoologique (1809), and Histoire naturelle des animaux sans vertèbres (1815–1822).

Although Lamarck himself founded no school of thought, his ideas became a standard point of reference and controversy during the century that followed. His failure to develop a convincing theory of the transmutation of species—in an era increasingly favorable to biological mutability—can be traced to his inability to articulate a credible mechanism for such change. He rejected the idea of species extinction, and evolution through the natural selective pressures never occurred to him. Lamarck's own theory about the transmission of acquired traits from parents to offspring lacked empirical support, and he seems not to have appreciated the significance of biogeography or the fossil record offered by paleontology for developing a complete evolutionary account of life. His posthumous reputation suffered substantially from the campaign of Georges Cuvier (1769–1832) against the insufficiencies of his theory of the inheritance of acquired characteristics. Nevertheless, Lamarck played a seminal role in broaching the basic idea of species change and in supporting it with a justification that rivaled natural selection in plausibility until the integration of Mendelian genetics with the theory of Charles Darwin (1809–1882) after 1900.

Neo-Lamarckism was a late-nineteenth-century movement with variants in France, Britain, and North America. Following the publication Darwin's Origin of Species (1859), naturalists who were skeptical of Darwin's insistence on natural selection drew upon Lamarck's theory to elaborate an evolutionary science of life driven by an alternate mechanism. In France his main ideas were preserved through the efforts of his colleague Etienne Geoffroy Saint-Hilaire (1772–1844), and elaborated a generation later by biologists such as Alfred Giard (1846–1908). The neo-Lamarckian school in the United States was led by paleontologist Edward Cope (1840–1897) and other scientists who combined diligent fieldwork with a distinctive theistic metaphysic. Their journal The American Naturalist called for a new natural theology built upon perceived evidence of divine purpose in the environmental adaptation of organisms. In contrast, the French neo-Lamarckian school was secular in flavor, rejecting any intent of discovering divine purpose in nature, illustrating how neo-Lamarckism as a scientific theory was compatible with a wide variety of conflicting theological and metaphysical interpretations.

See also DARWIN, CHARLES; EVOLUTION; NEO-DARWINISM

PETER M. J. HESS