Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck

views updated

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck

1744-1829

French Naturalist and Systematist

Jean-Baptiste de Lamarck did much to clear the path toward the current theory of evolution and natural selection. While some of his ideas about evolution were later proven false, others led later scientists, including Charles Darwin (1809-1882), to develop the concepts that now form the basis of the biological sciences. Another of Lamarck's great contributions was the classification of invertebrates, a term he coined for animals lacking a backbone.

Lamarck was born in Bazentin-le-Petit in Picardy, north of France, the youngest of 11 children. His family fell into the upper class socially but not financially, and he would struggle with money matters throughout his life.

After a few years in a Jesuit seminary, Lamarck decided to continue his family's history of military service and joined the French army in 1761. When, seven years later, an accidental injury ended his military career, he began to pursue scientific studies with an emphasis on botany.

His botanical work led to the 1778 publication of the greatly successful Flore Française, which described the plants of France. The book helped Lamarck win admission to the French Academy of Sciences in 1779 and to land a position as assistant botanist at the Jardin des Plantes, which specialized in its botanical gardens, along with studies of medicine, chemistry, and biological sciences.

A reorganization of the Jardin des Plantes into the Musée National d'Histoire Naturelle (National Museum of Natural History) in 1793 eliminated the need for Lamarck as a botanist and instead catapulted him into the position of professor of the natural history of "insects and worms." Although he was nearly 50 years old and lacked a background in the field, Lamarck quickly switched gears and began a study of these animals, for which he introduced the term invertebrates.

At the museum, Lamarck became a renowned systematist. He recognized the differences between insects, spiders and other arachnids, and worms and other annelids, and he classified them into separate groups. He explained his classification system in Systéme des animaux sans vertébres (System of Invertebrate Animals) published in 1801, and the seven-volume Histoire naturelle des animaux sans vertébres (Natural History of Invertebrate Animals), published from 1815-1822.

Shortly after the turn of the century, Lamarck began to voice his views on evolution. He believed that species changed over time, and that current species were the descendants of earlier forms. He also helped shift the widely accepted evolutionary depiction of a "chain of being," which was a straight line, into a branching tree.

He is best known, however, for what has come to be known as the "use and disuse" hypothesis. He felt that species mutated over time to adapt to changes in the environment. If an animal found itself in a drier habitat, for example, it might over the generations develop thicker skin to avoid desiccation. Other organs followed this pattern. Lamarck also often suggested that organisms could "will" the change in themselves. For example, a deer-like animal that wanted to eat the upper-level leaves on tall trees could stretch its neck, which eventually would lengthen. Over the generations, this continued activity would give rise to giraffes. He said that if humans followed this path, their desire to become the dominant species might result in the development of bipedal locomotion and larger brains.

Lamarck's "use and disuse" hypothesis drew increasing fire, and the emerging field of genetics in the 1900s sealed its fate as a false notion.

Despite his fine reputation as a systematist, Lamarck remained a pauper most of his life. Nonetheless, he was married four times and had several children, two of whom cared for him when he lost his sight late in life. He died in poverty in 1829. The lease on his rented gravesite ran out a few years after his death, and the location of his remains is unknown.

LESLIE A. MERTZ

About this article

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck

Updated About encyclopedia.com content Print Article Share Article