discuss the arguments in favour against lamarckism
Answers
Answer:
Lamarckism, a theory of evolution based on the principle that physical changes in organisms during their lifetime—such as greater development of an organ or a part through increased use—could be transmitted to their offspring. The doctrine, proposed by the French naturalist Jean-Baptiste Lamarck in 1809, influenced evolutionary thought through most of the 19th century. Lamarckism was discredited by most geneticists after the 1930s, but certain of its ideas continued to be held in the Soviet Union into the mid-20th century
Explanation:
n On the Origin of Species, Charles Darwin accepted the principle of the inheritance of acquired characteristics as one of the factors contributory to evolution. This endorsement of Lamarckism has resulted in some confusion in terminology. Thus, in the Soviet Union, Lamarckism was labeled “creative Soviet Darwinism” until it lost its official endorsement in 1965. In Variation of Animals and Plants Under Domestication, Darwin elaborated his view and proposed a “provisional hypothesis” to explain the transmission. This hypothesis he called pangenesis. Each part of the body was imagined to throw off invisible particles called “gemmules,” which, passing into the blood stream, were supposed to collect in the germ cells and there combine with like units already present, modifying them in accordance with the changes that had taken place in the peripheral organs from which they came. Thus the next generation arising from the germ cells is a photograph, as it were, of the parent at the particular stage when the germ cells were formed. It is, perhaps, almost needless to point out that this vague conception of the mode of development of the germ cells is totally at variance with modern knowledge concerning the origin of eggs and spermatozoa, which in many cases are present and often developed before the adult stages are reached.
Charles Darwin: On the Origin of Species
Charles Darwin: On the Origin of Species
Title page of Charles Darwin's On the Origin of Species by Means of Natural Selection, 1859.
Library of Congress, Washington, D.C. (neg. no. LC-USZ62-95224)
August Weismann’s challenge of the entire theory of the transmission of acquired characteristics marks a turning point from the older credulous attitude to the modern demand for more critical evidence. Weismann’s conclusions, based on a few questionable experiments, can scarcely be regarded as convincing. For example, Weismann cut off the tails of mice for many consecutive generations without creating a tailless type. This, he felt, was evidence against the theory of inheritance of acquired characteristics. Darwin had, in fact, already pointed out that the loss of a part is not inherited because the germ material already contains the inherited units for the development of each part. Nevertheless, the admission weakens the argument that organs become rudimentary through disuse. Weismann succeeded in showing the inadequacy of much of the evidence generally accepted by Lamarckians in support of their views, and he pointed out that the continuity of the germ plasm suffices to account for the inheritance of the great majority of characteristics common to all individuals of a species without the need of postulating contributions from the body cells.
Weismann, August
Weismann, August
August Weismann.
The discussion was also carried on by several paleontologists, among them Alpheus Hyatt, Edward D. Cope, and, at one time, Henry F. Osborn. In fact, as early as 1833, Sir Charles Lyell had reported Lamarck’s views and reprinted them in later editions of his famous Principles of Geology, treating the evidence, however, with great caution and skepticism. The doctrine also appealed to some psychologists and popular writers, such as Ewald Hering and Samuel Butler, owing to a fancied resemblance of heredity to memory. Others, impressed by the difficulty of explaining coordinated reactions and instincts unless nervous reactions are inherited, have resorted to Lamarck’s doctrine. The inheritance of acquired characteristics was also maintained by the English philosopher Herbert Spencer.