Lamarck

Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck was a 19th century biologist (he, in fact, coined the term "biology") who developed a now discredited theory of evolution. Whilst the ideas involved were not originated by Lamarck he has come to personify pre-Darwinian ideas on evolution.

Born into poor nobility (hence 'chevalier'), Lamarck served in the army before becoming interested in [natural history]? and writing a multi-volume flora of France. This caught the attention of Le Compte de Buffon? who arranged for him to be appointed to the Musee d'Histoire Naturelle in Paris. After a number of years working on plants, Lamarck was appointed curator of invertebrates? (another term he coined), and began a series of public lectures. Prior to 1800, he was an essentialist who believed that species were unchanging. Due to his work on the mollusc?s of the Paris Basin, he became convinced that transmutation occurred over time, and set out to develop an explanation (which he outlined in his 1809 publication, Philosophie Zoologique).

His theory rested on two 'observations' which were accepted by virtually all observers at the time, namely;

1. Use and disuse - Individuals lose characteristics they do not require and exaggereate those that are useful.
2. Inheritance of acquired traits - examples that are usually used include: stretching of giraffes necks to reach leaves leads to offspring with longer necks; strengthening of the muscles in a blacksmith's arm leading to sons with similar muscular development.

With this in mind, he developed his two laws;

1. Law 1
2. Law 2

The mechansisms of evolution were the movements of bodily fluids to much used organs, causing swelling and enlargement of these features. expand

Lamarck saw [spontaneous generation]? as being ongoing, with the simple organismas thus created being transmuted over time (by his mechanism) becoming more complex and closer to some notional idea of perfection. He thus believed in a teleological? (goal-oriented) process where organisms became more perfect as they evolved.

Lamarck is perhaps unfortunate to be so villified by modern theorists, he at least believed in organic evolution and at the time there was no other theoretical framework to explain these beliefs. He also argued that function precedes form, an issue of some contention among evolutionary theorists at the time. On the other hand, the inheritance of acquired characteristics is now widely refuted. [August Weismann]? disproved the theory by cutting the tails off mice, demonstrating that the injury was not passed onto the offspring. Indeed Jews and other religious groups have been circumcising men for hundreds of generations without any noticible withering of the foreskin amongst their descendants. However Lamarck did not count injury or mutilation as a true acquired characteristic, only those which were initiated by the animal's own needs were deemed to be passed on.

Charles Darwin praised Lamarck in the third edition of The Origin of Species for supporting the concept of evolution and bringing it to the attention of others. Indeed, Darwin accepted the idea of use and disuse, and developed his theory of pangenesis partially to explain it's apparent occurence. It was not Darwin who killed theories of the inheritance of acquired characteristics, but the discovery of cellular mechanisms of inheritance? and genetics (both ideas that Darwin acknowledged he required to complete his theory).