Lamarcks Evolution Theory

Lamarckian-Lysenko doctrine = Lamarckian-ism = Lamarckism. The French naturalist/evolutionist Jean-Baptiste Pierre Antoine de Monet Lamarck (1744-1829) presented his theory of evolution in 1800 in a public lecture in which he proposed the first coherent theory of the process of evolution prior to Darwin's theory of natural selection (Lamarck also proposed the heredity predisposition theory, which is used often in relation to pathological conditions, such as schizophrenia, to explain the conduct of a person who appears to have inherited a predisposition towards a particular trait or characteristic; such pathology is presumed to develop only in the appropriate environmental context). Lamarck formulated four "laws" in this theory: (1) there is a natural tendency toward increasing organic complexities; (2) new organs evolve by indirect environmental influences; (3) there is a use-disuse principle operative in changes to an organ where parts of the body used extensively to cope with the environment become larger and stronger and - where new habits are acquired -useless organs disappear; and (4) acquired characteristics are inheritable. Lamarck published his theory of evolution in 1809, the year Charles Darwin was born. Out of his interest in zoology and by comparing current species to fossil forms, Lamarck observed several lines of descent where each line was a chronological series of older to younger fossils leading to a modern species. To illustrate his use-disuse principle, Lamarck cited examples of the blacksmith who develops a bigger bicep in the arm that works the hammer and a giraffe stretching its neck to new lengths in pursuit of tree-leaves to eat. The principle of inheritable acquired characteristics presumes that the modifications an organism acquires during its lifetime may be passed along to its offspring. However, there is no convincing evidence to support this principle, and most scientists today agree that acquired traits do not change genes transmitted by gametes to offspring -notwithstanding recent developments and techniques in biology called genetic engineering, recombinant DNA, and gene cloning where genetic manipulations can cause profound organismic changes and where the term acquired characteristics may require redefinition. Modern geneticists have affirmed that inheritance is determined solely by the reproductive cells and is unaffected by somatic (body) cells. Therefore, belief in the inheritance of acquired characteristics is rejected, generally, today. Although the Lamarckian theory of evolution may be ridiculed by some people today because of its inheritable acquired characteristics assumption, that aspect of inheritance was accepted widely in Lamarck's time, and even Darwin himself could offer no acceptable alternative. Also, the con cept of inheritable acquired characteristics seems to have some survival value where it has been revived in certain contexts and in various guises (cf., the notion of meme - a self-replicating cultural element or pattern of behavior analogous to a gene but transferred from one individual to another via memory and imitation rather than genetic transmission) by several early and modern biologists and psychologists, for example, Jean Piaget, Herbert Spencer, William McDougall, and Carl Jung. In the 1930s, the Soviet geneticist and agronomist Trofim Denisovich Lysenko (1898-1976) formulated a neo-Lamarckian theory of genetics (also called Lysenkoism) that suggested that environment may alter the hereditary material. Lysenko rejected the popular doctrine of neo-Mendelism, and his theories were offered as Marxist orthodoxy, which won the official support of the Soviet government. However, during the 1950s, Soviet physicists and mathematicians had gained status and strength with the growth of the Soviet space program and, as scientific support grew for Francis Crick and James Watson's model of DNA in 1953, criticism mounted against Lysenko and his ideas. Lysenko was forced to resign his position as director of the Institute of Genetics and the Soviet Academy of Sciences in 1965. In the final analysis, Lamarck probably deserves some credit for his unorthodox theory, which was visionary in may respects: it claimed that evolution is the best explanation for both the fossil record and the current diversity of life, it emphasized the great age of Earth, and it stressed adaptation to the environment as a primary product of evolution. See also DARWIN'S EVOLUTION THEORY; MENDEL'S LAWS/PRIN-CIPLES; USE, LAW OF; WEISMANN'S THEORY. REFERENCES

Lamarck, J. (1809). Zoological philosophy: An exposition with regard to the natural history of animals. London: Macmillan.

Lysenko, T. D. (1948). Agrobiology. Moscow: Foreign Languages Publication House.

Watson, J., & Crick, F. (1953). Molecular structure of nucleic acids. A struc-

ture for deoxyribose nucleic acid. Nature, 171, 737-738. Dawkins, R. (1999). The extended phenotype.

The long reach of the gene. New York: Oxford University Press.

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