The French naturalist Jean-Baptiste Lamarck (1744-1829) was one of the key influences on Darwin's thought. Lamarck's most important book was the Philosophie Zoologique (1809) in which he argued that over time species change into new species.

However, the way in which he thought species changed was importantly different from Darwin's and our modern idea of evolution, and the term Lamarckism now usually refers to his misconception that acquired characteristics can be inherited.