Lamarck was born in the small town of Bazentin in northern France, the scion of an impoverished aristocratic family. He served in the military during the Seven Years War and, at the age of only 17, was awarded a commission for bravery in recognition of his actions on the battlefield. It was at this point that Jean-Baptiste Pierre Antoine de Monet (Lamarck's given name) became the Chevalier de Lamarck, or Jean-Baptiste Lamarck, the name by which he was thereafter known.
Later, when Lamarck retired injured, he took up a new career in natural history. He first studied botany under the naturalist Bernard de Jussieu. The eventual product of this ten-year period of research was Lamarck's Flore françoise (1778), a three-volume work on the plant life of France that brought its author into the front rank of French naturalists.
Lamarck eventually obtained a position at the Jardin des Plantes in Paris, and later at the Muséum national d'Histoire naturelle where he became a professor of zoology. In 1801, he published Système des Animaux sans Vertebres, a landmark in invertebrate taxonomy. It was he who originated the distinction between vertebrates and invertebrates, and who introduced many still-existing major divisions of the latter category, such as crustaceans, arachnids and annelids.
Lamarck's theory of evolution. Lamarck is now best remembered for his proposals concerning evolution. He was the first scientist to formally propose a gradualistic theory of evolution (as opposed to saltationist theories of evolution such as that proposed earlier by Linnaeus). As Darwin (Origin, 3rd ed., p. xiii) put it,
Lamarck was the first man whose conclusions on this subject excited much attention. This justly-celebrated naturalist first published his views in 1801, and he much enlarged them in 1809 in his Philosophie Zoologique, and subsequently, in 1815, in his Introduction to his Hist. Nat. des Animaux sans Vertèbres. In these works he upholds the doctrine that all species, including man, are descended from other species. He first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition.
In his theory, Lamarck assumed that simple microscopic forms of life continuously arise spontaneously from nonliving matter. This notion that spontaneous generation occurs on an ongoing basis was still widely accepted in his day. But he further supposed that such forms had an innate tendency gradually to evolve over time into organisms of ever greater complexity. This was something no one else had said. Thus in 1803, he comments,
Do we not therefore see that through the action of the laws of organization ... nature has in favorable times, places, and climates multiplied the first germs of animal life, and allowed their organization to develop, ... and increased and diversified their organs? Then, ... aided by much time and by a slow and ongoing diversity of circumstances, she has gradually brought about in this way the state of things which we now observe. How grand is this consideration, and especially how distant is it from what is generally thought on this subject!
Under Lamarck's theory, traits could arise, or become more developed, through the use of an organ or portion of the body. For example, he said the necks of giraffes had gotten longer as they were used to stretch ever higher for leaves. Traits could also diminish, he claimed, through "disuse." In this way any organ that went unused would tend to shrink with the passing generations. For example, he said blind cave fish had become blind because their ancestors had not used their eyes.
This notion, that traits acquired in an individual's lifetime in response to exercise or environmental stimuli could be passed on to descendant generations, was not new. In those days, many people, even scientists, thought acquired traits could be inherited. But many other scientists opposed the idea, most prominently Cuvier. They ridiculed the idea with farcical scenarios such as cowboys fathering bowlegged babies or weight lifters producing muscle-bound children. However, many naturalists freely embraced the idea, including Darwin himself. For example, in the Origin (1859, pp. 479-480) he asserts that
Disuse, aided sometimes by natural selection, will often tend to reduce an organ, when it has become useless by changed habits or under changed conditions of life.
But Lamarck did not consider the inheritance of acquired traits crucial to his theory. The essential idea was an ongoing transformation of forms tending toward ever higher levels of complexity under the influence of natural laws.
He originated the idea of arranging organisms into genealogical trees of descent. As Locy (1915, pp. 131-132) notes, Lamarck
was the first to employ a genealogical tree and to break up the serial arrangement of animal forms. In 1809, in the second volume of his Philosophie Zoologique, as Packard has pointed out, he arranged animals according to their relationships, in the form of a trunk with divergent branches. This was no vague suggestion on his part, but an actual pictorial representation of the relationship between different groups of animals, as conceived by him. Although a crude attempt, it is interesting as being the first of its kind. This is so directly opposed to the idea of scale of being that we make note of the fact that Lamarck forsook that view at least twenty years before the close of his life and substituted for it that of the genealogical tree.
It is perhaps no coincidence that a former soldier, decorated for courage on the field of battle, was also the first scientist to suggest explicitly that human beings had evolved from apes (Philosophie Zoologique, 1809):
Certainly, if some race of apes, especially the most perfect among them, lost, by necessity of circumstances, or some other cause, the habit of climbing trees and grasping branches with the feet, … , and if the individuals of that race, over generations, were forced to use their feet only for walking and ceased to use their hands as feet, doubtless … these apes would be transformed into two-handed beings and … their feet would no longer serve any purpose other than to walk.
Perhaps he was a bit too courageous — his free tongue made him enemies among the very men who could have promoted his career — Jean-Baptiste Lamarck died in penury and ended in a rented grave. His remains were later exhumed when the five-year lease expired, and their ultimate destination is now unknown.
Major works of Jean-Baptiste Lamarck: Flore françoise (1778); Tableau encyclopédique et méthodique des trois règnes de la nature (1782-1832); Système des Animaux sans vertèbres (1801); Recherches sur l'organisation des corps vivants (1802); Philosophie Zoologique (1809); Histoire naturelle des animaux sans vertèbres (1815-1822).
Cited work: Locy, W. A. 1915. Biology and its makers. New York: Henry Hold.
Full Name: Though remembered as Jean-Baptiste Lamarck, his full name was actually Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck. As author, his name often appears as Jean-Baptiste de Lamarck.
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