Lamarck did NOT suggest anything like 'genetic' inheritance. He believed in the inheritance of acquired characteristics. That is, if your father built up his muscles, you could inherit them. (simplistic example, but relevant.)

"Two ideas were incorporated in Lamarck's theory. The first was the theory of use and disuse; the idea that body parts used more often become stronger and larger, while parts not used slowly waste away and disappear. The second idea was the inheritance of acquired characteristics theory, the concept that modifications that occur during an organisms lifetime are passed on to its offspring. His example was the giraffe. He believed that the long neck of the giraffe resulted from the ancestors of giraffes stretching their necks longer and longer while trying to reach the highest branches of the trees."

Lamarck was important because he got so much wrong, and gave us a window to what is NOT relevant. He did many useful things in regard to science & evolution and categorization, but he failed to see the proper connection between evolution and personal behavior.

(I was introduced to Lamarck in my 1st philosophy class in 1957, and he was being used as a bad example even bacvk then.)