Jean Baptiste de Lamarck
Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 – December 18, 1829) was a French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws.
Lamarck is usually remembered for his belief in the inheritance of acquired characteristics, and the "use and disuse" model by which organisms developed their characteristics. Lamarck incorporated this belief into his theory of evolution, along with other more common beliefs of the time, such as spontaneous generation.
With this in mind, Lamarck had developed two laws:
1 - In every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears.
2 - All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which their race has long been placed, and hence through the influence of the predominant use or permanent disuse of any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired modifications are common to both sexes, or at least to the individuals which produce the young.
Lamarck constructed what may be the first comprehensive theoretical framework of organic evolution. Stephen Jay Gould argues that Lamarck was the "primary evolutionary theorist", in that his ideas and the way in which he structured his theory set the tone for much of the subsequent thinking in evolutionary biology, through to the present day.
In the modern era, Lamarck is remembered primarily for a theory of "inheritance of acquired characters", called "soft inheritance" or Lamarckism. However, his descriptions of soft inheritance were, in fact, reflections of the folk wisdom of the time, accepted by most natural historians (including Charles Darwin in his Origin of Species). Lamarck's contribution to evolutionary theory consisted of the first truly cohesive theory of evolution, in which an alchemical complexifying force drove organisms up a ladder of complexity, and a second environmental force adapted them to local environments through "use and disuse" of characteristics, differentiating them from other organisms.
Lamarckism is used as an analogy to describe the action of other "evolutionary" concepts in the modern era. For example, the memetic theory of cultural evolution is sometimes described as a form of "Lamarckian" inheritance of non-genetic traits.
After publication of Charles Darwin's theory of natural selection, the importance of individual efforts in the generation of adaptation was considerably diminished. Later, Mendelian genetics supplanted the notion of inheritance of acquired traits, eventually leading to the development of the modern evolutionary synthesis, and the general abandonment of the Lamarckian theory of evolution in biology. In a wider context, soft inheritance is of use when examining the evolution of cultures and ideas, and is related to the theory of Memetics.