French naturalist and evolutionary theorist.
Born: August 1, 1744
Died: December 28, 1829

Lamarck became an expert in Botany after leaving the army due to an injury.
In 1778 he published a book on the plants of France, which got him appointed as an assistant botanist at the Royal Botanical Garden. In 1793 the garden was reorganized as the National Museum of Natural History and Lamarck was made a professor of "the natural history of insects and worms."
This was not something he knew anything about, and these animals were not widely studied at the time, so Lamarck had to learn the material even as he was essentially creating a new field of biology. He made several advances in this field.

Lamarck is better known for his work in evolutionary theory.
He started to publish his theory in 1801. The mechanism of change in his theory was:

  1. A change in environment changes the needs of organisms in the environment, so they alter their behavior to fulfill those needs.
  2. This change in behavior causes the organisms to use certain parts either more or less, which causes the parts in question to either grow or shrink.
  3. These changes are passed to the next generation via heredity.
Lamarck used much of the same evidence in support of his theories as did later theorists such as Darwin. However, they are different from more modern theories in other ways than the mechanism of change. For example, Lamarck believed that species that disappeared evolved into new species rather than becoming extinct. His theories were largely ridiculed in his time. However, they regained attention in the middle of the 19th century and were considered an alternative to the theories of Darwin until the beginning of the 20th century when the laws of Mendel, with which they were incompatible, were rediscovered.
When Lamarck died, he was buried in a rented grave.
"Lamarck was the first man whose conclusions on the subject excited much attention. This justly celebrated naturalist first published his views in 1801. . . he first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition."

Charles Darwin, 1861