what was Jean- Baptiste Lamarck contribution to our knowledge of evoulution

He was the first person to hypothesize that the environment played a role in how the organism evolved. Unfortunately, his idea that organisms evolve because they have to, or they need to wasn't correct.

Georges Buffon was the first scientist to assert that species could change over generations and that these changes could lead to the formation of new species. He speculated that the earth is at least 75 000 years old and that humans and apes are related. He made this connection by comparing the anatomy of both animals – a concept called the "unity of type," a precursor of comparative anatomy. He insisted that natural phenomena must be explained by natural laws rather than theological doctrine.

Baron Georges Cuvier studied fossils and noted that many of the fossils were of creatures no longer living on the planet. He noted that the deeper you dug (older strata), the more dissimilar the fossils are from current life. Also, from one stratum to the next, some new species appear while others disappear. He conclusion that extinctions must have been a common occurrence in the history of life. Instead of evolution and a flow of form, he suggested catastrophism. That is, local catastrophes would wipe out the organisms of that time and they would be replaced with newly created forms. His idea explained the fossils, but not the increasing complexity.

Lamarck was the first biologist to recognize the role of the environment when it comes to the changing of a species, in his theory of acquired characteristics. In this he states that animals strive to survive through the use or disuse of various parts of their bodies. Those that are used will be accentuated and become stronger while those that are not used will whither and disappear. The enhanced traits will then be passed on to the next generation.
The problem is that Lamarck has the driving force of change within the control of the organism – not the environment. It is as if to say, “If you want it bad, you can develop the traits needed to survive.”