Lamarck, Jean-Baptiste de

Lamarck, Jean-Baptiste de, was a notable naturalist and one of the first proponents of a theory of evolution or transformism…

Biography of Jean-Baptiste de Lamarck

Jean-Baptiste de Lamarck (1 August 1744 – 18 December 1829) was a notable naturalist and one of the first proponents of a theory of evolution or transformism. He contributed to the development of botany, palaeontology and zoology and was the first to use the term “biology”.

Life and work

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, was born on August 1st 1744 in the village of Bazentin-le-Petit, in Picardy, Northern France. He is the last of the eleven children of Marie-Françoise de Fontaines de Chuignolles and Philippe Jacques de Monet de Lamarck. Although he was part of a military family, his parents decided to impose him upon priesthood, as happened to the younger children in the less fortunate noble families. So he entered in the Jesuit School of Amiens in 1755. However, the absence of religious vocation led him to give up in 1759, after the death of his father.

In 1761, Lamarck begins a military career under the name of Chevalier de Saint-Martin. He fought heroically in the seven years ‘ war during which he obtained the title of infantry officer. After the war, he went through several garrisons along the mediterranean and eastern borders of France, where he developed an interest in botany.

Lamarck contracts a form of scrofula (tuberculous cervical lymphadenitis) in 1768 and was forced to leave the army. Next, he thought about starting a music career and at the same time he worked as an accountant in a bank in Paris. However, he abandoned quickly his musical ambitions and turned to medical studies as well as comparative anatomy and botany.

In 1779, he published the Flore Francoise (French Flora) in three volumes, in which he provides dichotomous keys very much easier to use than most methods of identification of the time.  This work brought him an immediate notoriety. In early 1780, Lamarck travelled through Europe as a correspondent of the Jardin du Roi (King’s Garden) and has returned with a collection of plants. He continued to study botany until the French revolution in 1789, when the Jardin du Roi was reorganized.

In 1793, Lamarck participated in the creation of the National Museum of Natural history which is part of the new botanical garden (old Jardin du Roi). At the age of 50, he became professor of zoology, a task split with another scientist, Geoffroy Saint-Hilaire. Lamarck was responsible for insects, worms and microscopic animals, which he called “invertebrates” and Saint-Hilaire for mammals, birds, reptiles and fish. In 1801, he published his Animals without Vertebrae System, in which he makes a review of the classification of invertebrates. The difficulties encountered in the preparation of this work caused the idea the existence of variability of species to arise for the first time. In 1804, he was distinguished, as all teachers of the Museum, with the National Order of the Legion of honour, order newly created by Napoleon I.

He published, in 1809, Philosophie zoologique, ou Exposition des considérations relatives à l’histoire naturelle des animaux (Zoological Philosophy, or exposure of the considerations regarding the natural history of animals), the best known of his works. In it, Lamarck outlines for the first time his theory of evolution, known as Lamarckism. From 1815 to 1820, he published seven volumes of his natural history of animals without vertebrae, showing the general characteristics of invertebrates, as well as their distributions, classes, families, genera, and citing the main species in each group.

From 1819, Lamarck suffers from blindness, making it impossible for him to write. With the help of his daughter Cornélie, to whom he dictates the text, he published his latest work “Système analytique des connaissances positives de l’homme” (“Analytical system of positive knowledge of man”) in 1820.

Father of eight children and three times widowed, Lamarck died poor, despite all his publications, on December 18th 1829 in his house at the Museum. His children had to apply for funds to pay for the funeral. He was buried in the Montparnasse cemetery and, later, his remains were deposited in the catacombs.

Lamarckism

Lamarckism designates the transformist theory developed by Lamarck when he was studying current and fossil molluscs. In fact, his observations led him to question himself about the process behind the succession of forms over time. Lamarck comes quickly to the conclusion that there is certain continuity and therefore that it happen a transformation from one form to another. Thus, a species do not become extinct, it only turns into a new species. According to him, the living things can be classified in a linear scale of increasing complexity. The different forms of animals appear one after another and derive from each other from small changes that accumulate over time, therefore counteracting the Creationist theory, which was dominant at that time.

Lamarckism is based on two laws that Lamarck described for the first time in his book Philosophie zoologique:

1st law – Law of use and disuse: The changes in the environment cause changes in organs. These are strengthened or weakened depending on its use or disuse.

2nd law – Law of transmission of acquired characteristics: The changes caused in certain characteristics of an organism, by its use or disuse, are transmitted to the descendants.

Lamarck used several examples to explain his theory. The best known is the giraffe that, according to him, had to gradually stretch the neck to reach the leaves in the trees, due to shortage of underbrush. This new feature was then transmitted to offspring until we get to the long-necked giraffes.

Lamarck’s theory was refuted by Weismann, in the early 20th century, after having conducted an experiment in which he cut the tail of mice and found that the descendants continued with normal tails.

Epigenetic inheritance

Recently, the concept of inheritance of acquired characteristics have gain renewed attention due to advances in the field of epigenetics, the study of changes in gene expression, hereditary and reversible changes, which do not involve a change in the DNA sequence.

In fact, recent studies, mainly with mice, have highlighted the transgenerational transmission of epigenetic changes. A good example of this is a study carried out in 2014, in which mice were conditioned to feel fear in the presence of a particular odour. It was then verified that this characteristic was transmitted to the next two generations. So, it seems that Lamarck wasn’t completely wrong.

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References:

  • Corsi, P. (2008). Chronologie de la vie de Jean-Baptiste Lamarck. Available: http://www.lamarck.cnrs.fr/chronologie/. Last accessed 20th Jul 2015.
  • Days, B.G. and Ressler, k. j. (2014). Parental olfactory experience influences behavior and neural structure in subsequent generations. Nature Neuroscience. 17 (1), 89-96.
  • Oakes, E. H (2007). Encyclopedia of world Scientists. 2nd ed. New York: Infobase Publishing. p423-424.
  • Van Soom, A., Peelman, L, Holt, W. V. and Fazeli, A. (2014). An Introduction to Epigenetics as the Link Between Genotype and Environment: A Personal View. Reproduction in Domestic Animals. 49 (3), 2-10.
  • Yount, L (2003). A to Z of Biologists. New York: Facts on File. p159-161.
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