Lamarck's theory of evolution differs from Darwin's in its premise that adaptations appear when needed in response to the environment and the acquired traits are then passed on to offspring. Genetic research, however, has shown that living organisms cannot alter their genetic material as needed. Darwin's theory differs from Lamarck's by describing evolution as a consequence of the environment instead of a response to it.
Jean-Baptiste Lamarck published his transmutation theory of evolution 50 years before Charles Darwin published his. Darwin most likely read Lamarck's publication and began his research into evolution in 1838. In 1859, after several years of travel and field study, Darwin published his famous work, "On the Origin of Species," which explained in detail his theory of natural selection. His theory proposed that there is a great deal of variety among offspring and that only those offspring which possessed the traits best suited to their environment were able to survive and reproduce. This explanation of the evolutionary process was later referred to as "survival of the fittest."
Lamarck's theory proposed that the changes a species undergoes and passes on to its offspring are a result of its inner striving toward perfection or an adaptation fueled by necessity. An example of Lamarckian evolution would be a man and a woman developing significantly stronger upper arms as a result of their professions or sports activities, and then producing children that also possessed stronger upper arms. Modern research into genetics has discredited this major premise of Lamarck's evolutionary theory.