Inheritance of acquired traits
The theory of the inheritance of acquired traits was formulated by the French naturalist Jean-Baptiste Lamarck. It signifies that the traits an organism acquires during its lifetime in correspondence to its environment will be transmitted to its offspring. According to this theory giraffes have long necks because shorter giraffes spent their lives stretching their necks to reach their food, foliage, and they passed on this trait to their young, creating over generations the modern giraffe. This theory, however, was never proven scientifically (and in fact disproven by genetics) and was replaced by Darwin's theory of natural selection. Lamarck believed that species changed of their own free will and if a limb or body part was not used, the body part could completely fall off or disappear if the animal wished it to.