The French naturalist and biologist Jean-Baptiste Lamarck was one of the earliest proponents of the evolutionary theory. Born in 1744 into an aristocratic family in Bazentin-le-Petit, Picardy, he initially pursued a military career but following a severe illness turned to zoology and botany. By the late eighteenth century, he had established himself as an eminent botanist, and in 1778 he published his first major work, Flore française, a comprehensive treatise of the flora of France. That year, he also became a member of the French Academy of Sciences.

In 1793, Lamarck became a professor of zoology at the National Museum of Natural History in Paris. His most significant contribution during this time was the publication of Système des animaux sans vertèbres in 1801, in which he coined the term “invertebrates” and established the distinction between them and vertebrates. This distinction is crucial in the study of zoology, as more than 90 percent of all living species are invertebrates, including a wide range of animals such as earthworms, sponges, jellyfish, lobsters, crabs, insects, spiders, snails, clams, sea stars, sea urchins, and squid. Lamarck’s research and classification of these organisms laid the foundation of modern zoology and significantly advanced the study of this discipline.

Though overshadowed by Charles Darwin, Lamarck played a critical role in science with his proposal of the inheritance of acquired characteristics. He outlined his theory in his seminal work Philosophie Zoologique (1809), arguing that species were not fixed but underwent gradual changes in response to their surroundings and that they could pass on these acquired traits to their offspring. He believed that all living organisms possessed an innate drive to adapt themselves to their environment. Giraffes, for example, had long necks because over generations they stretched them to reach higher leaves, and birds that needed to swim would likewise have developed webbed feet and passed on that acquired inherited trait to their descendants in subsequent generations.

Lamarck’s detailed classification of organisms formed an essential bridge between pre-Darwinian natural history and modern evolutionary biology. His theory of inheritance of acquired characteristics, though later discredited, was clearly visionary. By daring to question the immutability of species, he changed the prevailing view, supported by religion and ancient philosophy, that species were created in their current form and remained unchanged through time. In an indirect way, he had a lasting impact on the natural sciences, demonstrating how even flawed theories can contribute to great progress.