The French naturalist Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (1744-1829), is best known for his theory of organic evolution and his work on invertebrate animals.
Jean de Monet, Chevalier de Lamarck, was born Aug. 1, 1744, at Bazentin-le-Petit in Picardy. He studied for the priesthood, but on the death of his father in 1760 he joined the French army. When his military career ended because of illness in 1768, he went to Paris, where he began to study medicine. He also became interested in meteorology, chemistry, and botany.
Lamarck's scientific reputation was established with the publication of his Flore française (1778; French Flora), in which he combined the best of two competing systems of plant classification. This work brought him to the attention of the French naturalist the Comte de Buffon, who helped gain Lamarck's admission to the French Academy of Sciences in 1779. Buffon also secured an appointment for Lamarck as a representative of the Jardin des Plantes; in this capacity he traveled through Europe from 1780 to 1782 collecting botanical and mineralogical specimens. Then he began to write the Dictionnaire de botanique (3 vols., 1783-1789; Dictionnaire of Botany) and the Illustration des genres (1791-1800; Illustrations of the Genera) for the Encyclopédie méthodique (Methodical Encyclopedia). From 1784 to 1792 Lamarck also published many botanical articles, but the only botanical work to show the influence of Lamarck's theory of evolution was his Histoire naturelle des végétaux (1803; Natural History of Vegetables).
The Jardin des Plantes in Paris was an important scientific center for work in botany, zoology, chemistry, and mineralogy. At the time of the French Revolution, when all the institutions of the Old Regime were being examined, proposals were also made for the reorganization of the Jardin. However, in 1793, when the Academy of Sciences was suppressed for being too aristocratic, the Jardin was transformed into the Muséum National d'Histoire Naturelle (National Museum of Natural History). Because the posts in botany were filled by someone else, Lamarck was named professor of "Insects and Worms" (Carl Linnaeus's terms for invertebrates). Thus, at almost 50 years of age, Lamarck began a career in a completely new field.
Lamarck's chemical theories are usually dismissed as the product of unfortunate speculation because they represented the "old chemistry" overturned by Antoine Laurent Lavoisier and the "chemical revolution." However, they provide the key to his conception of nature and are essential features of his theory of evolution. Lamarck began his work in chemistry in the 1770s, when the four-element theory of matter (earth, air, fire, water) was still generally accepted in France. The fact that the most important element in his system was fire in its various states of modification allowed Lamarck to explain most of the known chemical and physical phenomena. His chemistry was also used to explain the mechanical interaction of individuals with the environment and, thus, evolution and the emergence of higher mental faculties.
The chemistry is presented in all of Lamarck's works dealing with evolution and in three main studies on the subject: Recherches sur les causes des principaux faits physiques (1794; Research on the Causes of the Principal Physical Facts); Réfutation de la théorie pneumatique (1796; Refutation of the Pneumatic Theory); and Mémoires de physique et d'histoire naturelle (1797; Memoirs on Physics and Natural History).
Lamarck's interest in meteorology dates from his early years in Paris. In fact, Lamarck's first known work in any field was the "Memoir on the Principal Phenomena of the Atmosphere" (1776); he later published a number of articles on the subject. Lamarck's work in this field is also generally dismissed as a collection of unfounded theories. He speculated that atmospheric change was caused by a tidal effect on the earth's atmosphere produced by the sun and the moon. He adhered to the characteristic 18th-century belief that there was a simple law which would describe and predict the weather; this course seemed possible after Benjamin Franklin's work with lightning and the progress of various sciences in the century.
The work in meteorology was also related to Lamarck's interests in biology; weather was a major environmental factor important to his theory of evolution. He believed that the importance of this field was that climate had a great influence on living organisms.
The Hydrogéologie (1802; Hydrogeology) presented Lamarck's geological views. He held that the earth was much older than the biblical account indicated. The history of the earth was one of continuous change brought about by the eroding effect of water followed by sedimentation as organic materials decayed. Great amounts of time were needed for the slow process of organic development. Evolution also required that the same factors producing geological change in the present had operated throughout the history of the earth; this view was later called uniformitarianism. These geological theories were necessary for Lamarck's theory of evolution.
When Lamarck accepted his appointment as professor of "Insects and Worms," a category comprising most of the animal kingdom, very little was known about invertebrates (a term introduced by Lamarck) or how to classify them. Lamarck began to study the many specimens in the Muséum, and he developed a system of classification. His work was publicized through his lectures, a number of monographs, and books, the most important of which were Système des animaux sans vertèbres (1801; System of Invertebrate Animals) and his seven-volume major work, Histoire naturelle des animaux sans vertèbres (1815-1822; Natural History of the Invertebrate Animals). Lamarck's study of the invertebrates had important influences on the development of his theory of evolution, for the lower invertebrates, representing life in its simplest form, helped him to formulate his ideas on the nature of life.
Lamarck laid the foundations of invertebrate paleontology in his Mémoires sur les fossiles des environs de Paris (1802-1806; Memoirs on the Fossils of the Paris Area). His treatment of fossils as organic remains and his recognition of their similarities to living forms were significant for the formulation of his views on evolution.
Lamarck's first suggestion of evolution appeared in 1800, and he went on to develop his evolutionary ideas in Recherches sur l'organisation des corps vivans (1802; Research on the Organization of Living Bodies). The Philosophie zoologique (1809; Zoological Philosophy) is his most famous full-length treatment of evolution. Some of his ideas were clarified and expanded in the "Introduction" to his Histoire naturelle des animaux sans vertèbres (1815; Natural History of Invertebrate Animals), the last presentation of his theory.
In the 18th century it was generally believed that God had created all living beings within the framework of a hierarchy or chain of being. At the bottom of the chain were the simplest forms of life; above them were the various kinds of plants, then animals, and finally man as the most complex creature of creation. Lamarck transformed this static chain of being into an evolutionary one; the complex organisms, he maintained, had evolved from simpler ones over a very long period of time.
A crucial question was the origin of the simplest form of life; Lamarck gave a materialistic definition of life and then, using his chemistry, explained that it originated spontaneously from the action of heat, light, electricity, and moisture on certain inorganic materials. He held that there were actually two forms of life produced, plant and animal, which then evolved along two separate paths. In the animal kingdom, there was not a straight line of development but, rather, a branching family tree.
To maintain that all animals, including man, had been produced in this fashion rather than having been created by God, Lamarck had to account for the origin and development of the higher mental faculties. Again his chemistry was essential; he held that the nervous fluid (a modified form of fire) was the physical cause of these phenomena at various levels in the evolution of the nervous system.
To complete his theory of evolution, Lamarck formulated four laws (1815) to explain how complex life forms arise from simpler ones: "Law 1: Life, by its own forces, continually tends to increase the volume of every body which possesses it and to enlarge the size of its parts up to a limit which it brings about itself. Law 2: The production of a new organ in an animal body results from the appearance of a new want or need, which continues to make itself felt, and from a new movement which this want gives birth to and maintains. Law 3: The development of the organs and their strength of action are constantly in proportion to the use of these organs. Law 4: All that has been acquired, impressed upon, or changed in the organization of individuals during the course of their life is preserved by generation and transmitted to the new individuals that come from those which have undergone those changes." It should be noted that Lamarck's theory of evolution is completely materialistic in the context of its time.
Lamarck died in Paris on Dec. 18, 1829, blind, impoverished, and almost ignored by his countrymen. The eulogy read by his enemy Baron Cuvier condemned all of Lamarck's "fruitless" speculations, but it did offer faint praise for his biological classifications. The Neo-Lamarckians, who adopted only part of Lamarck's theory and changed much of it to suit their needs, were important toward the end of the 19th and beginning of the 20th century.
Only two of Lamarck's works are available in English: Zoological Philosophy, translated by Hugh Elliot (1963), and Hydrogeology, translated by Albert Carozzi (1964). A full-length study of Lamarck in English is Alpheus Packard, Lamarck, the Founder of Evolution (1901), which is somewhat dated and has a Neo-Lamarckian bias. Lamarck's place in the development of the theory of evolution is discussed in Hiram Bentley Glass and others, eds., Forerunners of Darwin, 1745-1859 (1959), and John C. Greene, The Death of Adam (1959). Important background books are Erik Nordenskiöld, The History of Biology, translated by Leonard Eyre (1928; new ed. 1935); Arthur Lovejoy, The Great Chain of Being (1936); and Herbert Butterfield, The Origins of Modern Science (1950; rev. ed. 1957).