Jean-Baptiste Lamarck (August 1, 1744 – December 18, 1829) was a French naturalist who proposed one of the first theories of evolution. He postulated a principle called inheritance of acquired characteristics, that an animal was able to change a characteristic during its lifetime depending on its behavior, and that these changes would be passed onto its offspring resulting in speciation. For example, if a giraffe attempted to eat the leaves off the top of a tree it would be constantly stretching its neck, resulting in both a longer neck for itself and that this characteristic would be passed onto its young.
Lamarck's theory was fundamentally flawed in that it could not explain the contradictions in observations, for instance a dog with a lobbed tail would not give birth to puppies without tails. The advent of biochemistry and genetics and discovery of DNA demonstrated the mechanisms by which characteristics were passed on, invariably disproving the theory.
Lamarckian evolution was upheld for decades in the 1900s by Trofim Lysenko, head of genetic and biological study within the Soviet Union, until he was discredited along with his pseudoscience in the 1960s.