Jean-Baptiste Lamarck

French naturalist 1744-1829

Jean-Baptiste Lamarck is best remembered for the incorrect hypothesis that evolutionary change occurs due to the inheritance of acquired characteris­tics. However, Lamarck’s contributions to biological thought are much more important than being the champion of a failed idea. He was the first really important thinker about evolution, and he established the central role of the environment in determining the adaptations of all types of organisms.

Born into a military family, Lamarck had a brief career as a soldier before turning his attention to medicine and science. His Flore Françoise (1778) on the plants of France brought him to the attention of French naturalist Comte de Buffon (Count Buffon), who became his sponsor in scientific circles. He was appointed professor at the National Museum of

Natural History, in charge of insects and “worms,” meaning all inverte­brates. Lamarck was the first to propose separating the arachnids (spiders), mollusks, and crustaceans from the insects, placing them in separate classes.

Lamarck’s appreciation of the enormous diversity of the invertebrates (a term he invented) strengthened his belief that species evolve over time. Lamarck proposed that environmental changes cause a change in an or­ganism’s needs, which leads to a change in behavior. For instance, scarce prey might lead to the need for a hawk to search the ground more carefully from a greater height. The increased use of its eyes would, according to Lamarck, improve the hawk’s eyesight. Furthermore, this acquired im­provement would be inherited by the hawk’s offspring over time. Alterna­tively, the disuse of an organ would cause it to shrink or weaken. Lamarck published his hypothesis in his book Philosophie Zoologique (1809).

Lamarck also believed that all animals were becoming progressively more complex and “perfect” over time, leading him to propose that spon­taneous generation accounted for the appearance of the simplest of or­ganisms.

We now know that heritable change cannot be induced by use or dis­use, but can only arise through changes in an organism’s deoxyribonucleic acid (DNA); nor does spontaneous generation occur. Despite his incorrect mechanism for evolution, Lamarck focused evolutionary thought on the idea of adaptation to the environment, an idea that was to be central to English naturalist Charles Darwin’s concept of natural selection fifty years later.

References

Magner, Lois E. History of the Life Sciences, 2nd ed. New York: Marcel Dekker, 1994.

Mayr, E. The Growth of Biological Thought. Cambridge, MA: Harvard University Press, 1982.