Introduction The study of different kinds of pieces of evidence of organic evolution confirms that evolution has definitely taken place in the organism. To explain the evolution in the organism, Lamarck proposed the theory of inheritance of acquired character which is known as Lamarckism. He wrote the book "Philosophic Zoologique" in which he elaborated on his doctrine of evolution. Lamarck is the first scientist who has made the first attempt to explain the origin of species and their adaptation to the environment. He was the first naturalist to conclude that evolution is a general fact covering all forms of life. Lamarckism states that changes which the organism acquires in adaptation to the environments which it meets during its whole life are automatically transferred to its descendants and so become part of the inheritance.
Assumptions of Lamarckism The theory of inheritance of acquired characters is comprised of the following four assumptions:
Examples of Lamarckism The following examples are given in favour of Lamarckism:
Evolution of long-necked Giraffe Giraffe is a mammal with a very long neck and long forelimbs. Lamarck presumed that the ancestors of giraffe lived in Africa were deer-like with a short neck and both fore and hind limbs were equal in size. They lived in places where the ground was almost invariably parched and without trees. When these ancestors were transferred to an area where there were only trees and no grass, they were continuously stretch their necks to reach the leaves of trees, high above the ground. The more and more use of neck and forelegs resulted in the lengthening of these organs. The continuous stretching for several generations resulted in the appearance of a long neck in giraffe.
Snakes Present-day snakes with the long slender body are evolved from a limbed lizard-like ancestors. Due to continuous disuse of limbs and stretching of their body to suit their creeping mode of locomotion and to accommodate their body in narrow space out of fear of larger and more powerful animals, the present-day snakes have been evolved.
Aquatic Birds Ducks and other aquatic birds have been evolved from terrestrial ancestors. Since they had invaded water from land in search of enough food because enough food was scared on land and these birds did not have the power to fly. The duck would stretch its toes apart to provide more push during swimming in water. This led to the development of webbed toes so that they could live in water easily.
Criticism of Lamarckism The greatest drawback in Lamarck's work was that it was too theoretical and there was no proof to support it. His ideas were based on theory but practically they had no standing. He met severe criticism from various scientists:
Neo-Lamarckism Many evolutionists were found to be supports the theory of inheritance of acquired characters. These come under the heading of Neo-Lamarckism. These evolutionists are Cope, Giard, Spencer, Mc. Bride, T.H. Morgan, etc. Neo-Lamarckism states that:
Conclusion The main error in Lamarckian thought and Neo-Lamarckism is that both assumed the inheritance of acquired characters. In Lamarckism, the acquired characters result from needs while according to Neo-Lamarckism these will be induced due to environment and habit. Use and disuse of Lamarck's thought were retained in Neo-Lamarckism.
Lamarckism and Neo-Lamarckism were not accepted by the scientists and after some years Darwin proposed the theory ofnatural selection to explain organic evolution.
Hakimuddin Kuwakhedawala is based in India with over 15 years experience as a teacher. Teaching and writing are his passion. Most of the articles of Hakimuddin are related to education, exam, environmental problems, etc.
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