Lamarckian

Lamarckism is a theory of biological evolution proposed by French biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck. It has since been discredited for multicellular organisms. It fell out of favour following Charles Darwin's Origin of Species which offerred an alternative method for evolution. However, Lamarckism is currently undergoing a revival, as epigenetic effects and particularly maternal effects are being discovered in an increasing number of species.

In a wider context, Lamarckism is of use when examining the evolution of cultures.

History
Developed in the early 19th century, Lamarckism held 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 (especially Acacias), 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&mdash;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&mdash;purely "acquired traits" do not appear in any meaningful sense to be inherited. For example, a human child must learn how to catch a ball even though his or her parents learned the same feat when they were children.

(Though it is important to note that just because the skill of catching a ball can not be passed on from parent to child does not mean that we can rule out all other traits from being passed on in a Lamarckian fashion).

The argument that instinct in animals is evidence for hereditary knowledge is generally regarded within science as false. Such behaviours are more probably passed on through a mechanism called the Baldwin effect. Lamarck’s theories gained initial acceptance because the mechanisms of inheritance were not elucidated until later in the 19th Century, after Lamarck's death.

Several historians of science 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 Charles 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. Note also that Darwin, like Lamarck, lacked a plausible alternative mechanism of inheritance - the particulate nature of inheritance was only to be observed by Gregor Mendel somewhat later, published in 1866. Its importance, although Darwin cited Mendel's paper, was not recognised until the Modern evolutionary synthesis in the early 1900s. An important point in its favour at the time was that Lamarck's theory contained a mechanism describing how variation is maintained, which Darwin’s own theory lacked.

The discredited belief that Lamarckism holds for higher order animals is still clung to in certain branches of new-age pseudoscience under the term racial memory.

Lamarckism and single celled organisms
While Lamarckism has been discredited as an evolutionary influence for larger lifeforms, some scientists controversially argue that it can be observed among single celled organisms. Whether such mutations are directed or not also remains point of contention.

In 1988 John Cairns at the Radcliffe Infirmary in Oxford, England and a group of other scientists renewed the Lamarckian controversy (which by then had been a dead debate for many years). The group took a mutated strain of E. coli that was unable to consume the sugar lactose and placed it in an environment where lactose was the only food source. They observed over time that mutations occurred within the colony at a rate that suggested the bacteria were overcoming their handicap by altering their own genes. Cairns et al dubbed the process adaptive mutagenesis.

If bacteria that had overcome their own inability to consume lactose passed on this "learned" trait to future generations, it could be argued as a form of Lamarckism; though Cairns later chose to distance himself from such a position. . More typically, it might be viewed as a form of ontogenic evolution.

Lamarckism and societal change
Jean Molino (2000) has proposed that Lamarckian evolution may be accurately applied to cultural evolution. This was also previously suggested by Peter Medawar (1959) and Conrad Waddington (1961).

Reference

 * Medawar, Peter (1959). "The threat and the glory". BBC Reith Lectures No. 6.
 * Molino, Jean (2000). "Toward an Evolutionary Theory of Music and Language". In Brown, Merker & Wallin (Eds.), The Origins of Music, ISBN 0-26-223206-5.
 * Waddington, Conrad (1961). The human evolutionary system. In: Michael Banton (Ed.), Darwinism and the Study of Society. London: Tavistock.
 * Cairns, J., J. Overbaugh, and S. Miller. 1988. Nature 335: 142-145
 * Culotta, Elizabeth; "A Boost for 'Adaptive' Mutation," Science, 265:318, 1994.)

Lamarckismus Lamarckismo לאמארקיזם Lamarckisme Lamarkizm Lamarckismi Lamarckism Ламаркизм