Lamarckism

From Freepedia

Lamarckism is a disputed theory of biological evolution proposed by French biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck. Developed in the early 19th century, Lamarckism holds that traits acquired (or diminished) during the lifetime of an organism can be passed on to the offspring. Lamarck based his theory on two observations, in his day considered to be generally true:

1. Use and disuse – Individuals lose characteristics they do not require (or use) and develop characteristics that are useful.
2. Inheritance of acquired traits – Individuals inherit the traits of their ancestors.

Examples of Lamarckism would include:

• Giraffes stretching their necks to reach leaves high in trees, strengthen and gradually lengthen their necks. These giraffes have offspring with slightly longer necks.
• A blacksmith, through his work, strengthens the muscles in his arms. His sons will have similar muscular development when they mature.

With this in mind, Lamarck 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.

In essence, a change in the environment brings about change in "needs" (besoins), resulting in change in behavior, bringing change in organ usage and development, bringing change in form over time—and thus the gradual transmutation of the species. While such a theory might explain the observed diversity of species and the first law is generally true, the main argument against Lamarckism is that experiments simply do not support the second law—purely "acquired traits" are not inherited. The mechanisms of inheritance were not elucidated until later in the 19th Century, after Lamarck's death.

Several science historians have argued that Lamarck's name is linked somewhat unfairly to the theory that has come to bear his name, and that Lamarck deserves credit for being the first to propose the concept of biological evolution, far more than for the mechanism of evolution, in which he simply followed the accepted wisdom of his time. Lamarck died 30 years before the first publication of Darwin's Origin of Species. As science historian Stephen Jay Gould has noted, if Lamarck had been aware of Darwin's proposed mechanism of natural selection, there is no reason to assume he would not have accepted it as a more parsimonious alternative to his "own" mechanism.

Jean Molino (2000) has proposed that Lamarckian evolution may be accurately applied to cultural evolution.

See also

• Epigenetic inheritance
• Lysenkoism
• Orthogenesis
• Obsolete scientific theories

Reference

• Molino, Jean (2000). "Toward an Evolutionary Theory of Music and Language", The Origins of Music, Brown, Merker, and Wallin, eds. ISBN 0262232065.