Jean-Baptiste Lamarck

  Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 – December 18, 1829) was a French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws. Lamarck was born as the eleventh child in an impoverished noble family of soldiers in Picardie. Lamarck was forced into enrollment in a Jesuit college in Amiens, but after his father's death in 1760, Lamarck joined a company of soldiers.^[1] He fought in the Pomeranian War with Prussia, and was awarded a commission for his bravery on the battlefield. At his post in Monaco, Lamarck became interested in natural history and resolved to study medicine.^[2] He retired from the army after being injured in 1766, and he continued to his medicine studies. Lamarck showed a particular interest for botany, and he studied the subject under Bernard de Jussieu for nearly ten years. He was one of the main contributors to the Cell Theory.

After publishing a respected three-volume work Flore Français, he gained membership into the French Academy of Sciences in 1779, with the help of Georges-Louis Leclerc, Comte de Buffon. Lamarck became involved in the Jardin des Plantes and was appointed to the Chair of Botany in 1788. When the Muséum national d'histoire naturelle was founded in 1793, Lamarck was appointed as a professor of zoology. In 1801, he published Système des Animaux sans Vertebres, a major work on the classifications of invertebrates. In an 1802 publication, he became one of the first to use the term biology in its modern sense.^[3][4] Lamarck continued his work as a premier authority on invertebrate zoology. In the modern era, Lamarck is remembered primarily for a theory of "inheritance of acquired characters", called "soft inheritance" or Lamarckism. His descriptions of soft inheritance were accepted by most natural historians (including Charles Darwin in his Origin of Species). Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through "use and disuse" of characteristics, differentiating them from other organisms.^[5]

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Biography

  Lamarck was born in Bazentin-le-Petit, Picardie, northern France,^[6] as the eleventh child in an impoverished aristocratic family.^[7] Male members of the Lamarck family had traditionally served in the French army. Lamarck's eldest brother was killed in combat at the Siege of Bergen-op-Zoom, and two other brothers were still in service when Lamarck was in his teenage years. Yielding to the wishes of his father, Lamarck enrolled in a Jesuit college in Amiens in the late 1750s.^[8] After his father died in 1760, Lamarck bought himself a horse, and rode across the country to join the French army, which was in Germany at the time. Lamarck showed great physical courage on the battlefield in the Pomeranian War with Prussia, and he was even nominated for the lieutenancy.^[9] However, when one of his comrades playfully lifted him by the head, he sustained an inflammation in the lymphatic glands of the neck, and he was sent to Paris to receive treatment.^[10] He underwent a complicated operation, and continued his treatment for a year.^[11] He was awarded a commission and settled at his post in Monaco. It was there that he encountered Traite des Plantes usuelles, a botany book by James Francis Chomel.^[2]

With a reduced pension of only 400 francs a year, Lamarck resolved to pursue a profession. He attempted to study medicine, and supported himself by working in a bank office.^[2] Lamarck studied medicine for four years, but gave it up under his elder brother's persuasion. He was interested in botany, especially after his visits to the Jardin du Roi, and he became a student under Bernard de Jussieu, a notable French naturalist.^[12] Under Jussieu, Lamarck spent ten years studying French flora. After his studies, in 1778, he published some of his observations and results in a three-volume work, entitled Flore Français. Lamarck's work was respected by many scholars, and it launched him into prominence in French science. On August 8, 1778, Lamarck married Marie Anne Rosalie Delaporte.^[13] Georges-Louis Leclerc, Comte de Buffon, one of the top French scientists of the day, mentored Lamarck, and helped him gain membership to the French Academy of Sciences in 1779 and a commission as a Royal Botanist in 1781, in which he traveled to foreign botanical gardens and museums.^[14] Lamarck's first son, André, was born on April 22, 1781, and he made colleague André Thouin the child's godfather.

In his two years of travel, Lamarck collected rare plants that were not available in the Royal Garden, and also other objects of natural history, such as minerals and ores, that were not found in French museums. On January 7, 1786, his second son, Antoine, was born, and Lamarck chose Antoine Laurent de Jussieu, Bernard de Jussieu's nephew, as the boy's godfather.^[15] On April 21 of the following year, Charles Rene, Lamarck's third son, was born. René Louiche Desfontaines, a professor of botany at the Royal Garden, was the boy's godfather, and Lamarck's elder sister, Marie Charlotte Pelagie De Monet was the godmother.^[15] In 1788, Buffon's successor at the position of Intendant of the Royal Garden, Charles-Claude Flahaut de la Billaderie, comte d'Angiviller, created a position for Lamarck, with a yearly salary of 1,000 francs, as the keeper of the herbarium of the Royal Garden.^[16]

  In 1790, at the height of the French Revolution, Lamarck changed the name of the Royal Garden from Jardin du Roi to Jardin des Plantes, a name that did not imply such a close association with King Louis XVI.^[17] Lamarck had worked as the keeper of the herbarium for five years before he was appointed curator and professor of invertebrate zoology at the Muséum national d'histoire naturelle in 1793.^[18] During his time at the herbarium, Lamarck's wife gave birth to three more children before dying on September 27, 1792. With the official title of "Professeur d’Histoire naturelle des Insectes et des Vers", Lamarck received a salary of nearly 2,500 francs per year.^[19] The following year on October 9, he married Charlotte Reverdy, who was thirty years his junior.^[15] On September 26, 1794, Lamarck was appointed to serve as secretary of the assembly of professors for the museum for a period of one year. In 1797, his second wife Charlotte died, and he remarried Julie Mallet the following year, who later died in 1819.^[15]

In his first six years as professor, Lamarck published only one paper, in 1798, on the influence of the moon on the earth's atmosphere.^[20] Lamarck began as an essentialist who believed species were unchanging; however, after working on the molluscs of the Paris Basin, he grew convinced that transmutation or change in the nature of a species occurred over time.^[21] He set out to develop an explanation, and on the 11th of May 1800 (the 21st day of Floreal, Year VIII, in the revolutionary timescale used in France at the time), he presented a lecture at the Museum de'Histoire Naturelle in which he first outlined his newly developing ideas about evolution.

In 1801, he published Système des Animaux sans Vertebres, a major work on the classification of invertebrates. In the work, he introduced definitions of natural groups among invertebrates. He categorized echinoderms, arachnids, crustaceans and annelids, which he separated from the old taxon for worms known as Vermes.^[22] Lamarck was the first to separate arachnids from insects in classification, and he moved crustaceans into a separate class from insects. In the class Crustaces, Lamarck proposed two orders. The first group was Crustaces pediocles, classified by the animals' two distinct stalked eyes. This categorization included crabs, shrimps and hermit crabs. The second group Crustaces sessiliocles were classified by the animals' distinct pair of eyes, or single, sessile eyes. Members of this order included amphipods, isopods, cyclops, cladocerans, xiphosurida and amymones.^[23]

In 1802 Lamarck published Hydrogéologie, and became one of the first to use the term biology in its modern sense.^[3][24] In Hydrogéologie, Lamarck advocated a steady-state geology based on a strict uniformitarianism. He argued that global currents tended to flow from east to west, and continents eroded on their eastern borders, with the material carried across to be deposited on the western borders. Thus, the Earth's continents marched steadily westward around the globe.

That year, he also published Recherches sur l'Organisation des Corps Vivans, in which he drew out his theory on evolution. He believed that all life was organized in a vertical chain, with gradation between the lowest forms and the highest forms of life, thus demonstrating a path to progressive developments in nature.^[25]

During his lifetime he became controversial, attacking the chemistry proposed by Lavoisier and criticising palaeontologist Georges Cuvier’s anti-evolutionary stance. After his death, Cuvier used the forum of an eulogy in an attempt to discredit Lamarck's scientific beliefs, painting a picture of Lamarck as the equivalent of a philosopher or poet (in fact, Lamarck was a strict materialist).

Lamarck died in Paris on December 18, 1829.^[26]

Lamarckian Evolution

Lamarck stressed two main themes in his biological work. The first was that the environment gives rise to changes in animals. He cited examples of blindness in moles, the presence of teeth in mammals and the absence of teeth in birds as evidence of this principle. The second principle was that life was structured in an orderly manner and that many different parts of all bodies make it possible for the organic movements of animals.^[25]

Although he was not the first thinker to advocate organic evolution, he was the first to develop a truly coherent evolutionary theory. He outlined his theories regarding evolution first in his Floreal lecture of 1800, and then in three later published works:

• Recherches sur l'organisation des corps vivans, 1802.
• Philosophie Zoologique, 1809.
• Histoire naturelle des animaux sans vertebres, (in seven volumes, 1815-1822).

Lamarck employed several mechanisms as drivers of evolution, drawn from the common knowledge of his day and from his own belief in chemistry pre-Lavoisier. He used these mechanisms to explain the two forces he saw as comprising evolution; a force driving animals from simple to complex forms, and a force adapting animals to their local environments and differentiating them from each other. He believed that these forces must be explained as a necessary consequence of basic physical principles, favoring a materialistic attitude toward biology.

Le pouvoir de la vie: The complexifying force

Lamarck referred to a tendency for organisms to become more complex, moving 'up' a ladder of progress. He referred to this phenomenon as Le pouvoir de la vie or la force qui tend sans cesse à composer l'organisation (The force that perpetually tends to make order). Like many natural historians, Lamarck believed that organisms arose in their simplest forms via spontaneous generation.

Lamarck ran against the modern chemistry promoted by Lavoisier (whose ideas he regarded with disdain), preferring to embrace a more traditional alchemical view of the elements as influenced primarily by earth, air, fire and water. He asserted that the natural movements of fluids in living organisms drove them toward ever greater levels of complexity:

The rapid motion of fluids will etch canals between delicate tissues. Soon their flow will begin to vary, leading to the emergence of distinct organs. The fluids themselves, now more elaborate, will become more complex, engendering a greater variety of secretions and substances composing the organs.

- Histoire naturelle des animaux sans vertebres, 1815.

He argued that organisms thus moved from simple to complex in a steady, predictable way based on the fundamental physical principles of alchemy. In this view, simple organisms never disappeared because they were constantly being created by spontaneous generation in what has been described as a 'steady-state biology'. Lamarck saw spontaneous generation as being ongoing, with the simple organisms thus created being transmuted over time becoming more complex. He is sometimes regarded as believing in a teleological (goal-oriented) process where organisms became more perfect as they evolved, though as a materialist, he emphasized that these forces must originate necessarily from underlying physical principles.

L'influence des circonstances: The adaptive force

The second component of Lamarck's theory of evolution was the adaptation of organisms to their environment. This could move organisms sideways from the ladder of progress into new and distinct forms with local adaptations. It could also drive organisms into evolutionary blind alleys, where the organism became so finely adapted that no further change could occur. This was later expanded in Charles Darwin's theories of species adaption and natural selection.

Lamarck argued that this adaptive force was powered by the interaction of organisms with their environment, by the use and disuse of characters:

In every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears.

These characters were then inherited, according to the common belief of the day, in what is known as "soft inheritance" (nowadays erroneously called Lamarckism):

All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which their race has long been placed, and hence through the influence of the predominant use or permanent disuse of any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired modifications are common to both sexes, or at least to the individuals which produce the young.

Legacy

Lamarck constructed what may be the first comprehensive theoretical framework of organic evolution. Stephen Jay Gould argues that Lamarck was the "primary evolutionary theorist", in that his ideas and the way in which he structured his theory set the tone for much of the subsequent thinking in evolutionary biology, through to the present day.^[27]

Lamarck is usually remembered for his belief in the inheritance of acquired characteristics, and the "use and disuse" model by which organisms developed their characteristics. Lamarck incorporated this belief into his theory of evolution, along with other more common beliefs of the time, such as spontaneous generation.

The inheritance of acquired characteristics (also called the theory of adaptation or "soft inheritance") was rejected by August Weismann when he developed a theory of inheritance in which "germ-plasm" (the hereditary material passed from parents to offspring) remained separate and distinct from "soma" (the material composing the body of an organism); thus nothing which happens to the soma may be passed on with the germ-plasm. This model underlies the modern understanding of inheritance. Weismann is famous for an experiment in which he cut the tails off mice, demonstrating that the injury was not passed on to the offspring; but historians of science such as Stephen Jay Gould argue that this experiment had far less effect on the acceptance of Lamarckism than Weismann's more comprehensive theoretical framework^[27] (Believers in Lamarckian inheritance did not count injury or mutilation as a true acquired characteristic: only those which were initiated by the animal's own needs, that were beneficial, were expected to be passed on. This Lamarckian view is consistent with Charles Darwin's theory of natural selection).

Lamarckism is used as an analogy to describe the action of other "evolutionary" concepts in the modern era. For example, the memetic theory of cultural evolution is sometimes described as a form of "Lamarckian" inheritance of non-genetic traits.

The honeybee subspecies Apis mellifera lamarckii is named after Lamarck. Likewise, the bluefire jellyfish (Cyaneia lamarckii) has been named after him.

See also

• Lamarckism
• Acclimation
• Exaptation
• Evolution
• Gene-centered view of evolution
• Intragenomic conflict
• Lysenkoism
• Maladaptation
• Neutral theory of molecular evolution
• Phenotypic plasticity
• Preadaptation
• Spandrel

Major Works

Lamarck's writings are available in facsimile and in word format (fr) at www.lamarck.cnrs.fr. Search engine allows full text search.

• 1809. Philosophie zoologique, ou Exposition des considérations relatives à l’histoire naturelle des animaux..., Paris.

On invertebrate classification:

• 1801. Système des animaux sans vertèbres, ou tableau général des classes, des ordres et des genres de ces animaux; présentant leurs caractères essentiels et leur distribution, d'après la considération de leurs..., Paris, Detreville, VIII : 1-432.
• 1815-1822. Histoire naturelle des animaux sans vertèbres, présentant les caractères généraux et particuliers de ces animaux..., Tome 1 (1815): 1-462; Tome 2 (1816): 1-568; Tome 3 (1816): 1-586; Tome 4 (1817): 1-603; Tome 5 (1818): 1-612; Tome 6, Pt.1 (1819): 1-343; Tome 6, Pt.2 (1822): 1-252; Tome 7 (1822): 1-711.

References