(ANTHROPOLOGY OPTIONAL PAPER –I)
Syllabus Section: 1.4 Human Evolution and the emergence of Man
Charles Darwin is known as the father of evolution due to his contribution to the establishment of the theory of evolution. Darwinism is the term coined for the explanation offered by Charles Darwin for the origin of species by natural selection. Darwin's theory of natural selection is based on several facts, observations and inferences. Darwin published his concept of evolution in his book entitled "The Origin of Species".
Darwin’s theory of natural selection:
- Darwinism consists of five principles which are:
- Prodigality of over production,
- Variation and Heredity,
- Struggle for existence,
- Survival of the fittest and
- Modifications of species.
- Over-production or prodigality of over-production: Many more individuals are born each generation than will be able to survive and reproduce.
- Variation and Heredity: There is natural variation among individuals et the same species. Many of the favorable adaptations are hereditary and are passed on to the progeny of future generations. (Darwin, like Lamarck believed in an incorrect theory of heredity: however, he interpreted the process in the proper context. Darwin himself was not satisfied with his blending theory of inheritance and as early as 1857 he wrote a letter to Huxley for an alternative to it.
- Struggle for existence: Organic beings increase by a geometrical ratio, while food production only increases in an arithmetic ratio. So that in a very short time, an area will be overpopulated with any one species, unless something happens to check the increase as a result there is a struggle for existence which is threefold as given below.
- Intraspecific struggle: The Intraspecific struggle is found among the Individuals of the same species. The competition is heavy in case of intraspecific struggle, because the needs and requirements of the members of the same species are same who live in the same environment. It is the most severe check on the rate of reproduction.
- Interspecific struggle: - It is found among organisms of different species living together. Members of one species struggle with other species for similar requirements i.e., food, shelter and mating.
- Struggle with the environment: Living organisms struggle with the adverse environmental conditions like floods, cold waves, heat waves and earthquakes, etc.
- Survival of the fittest or natural selection: Individuals with certain Characteristics have a better chance of surviving and reproducing than others with less favorable ones. (This is the concept of the survival of the fittest through favorable adaptations to the conditions of life).
- Modifications of species: Gradual modification of species could have occurred over the long periods of geological time through additive process occurring in the past in the same manner as they are occurring in the present.
Understanding the Concept of Natural Selection
The surviving individuals will give rise to the next generation. The successful variations are transmitted to the succeeding generations. The accumulation of advantageous traits in future generation gradually brings changes in species. Successive generations in this way tend to become better adapted to their environment. As the environment changes, further adaptations occur. The operations of natural selections occur for many generations. As a result, further changes occur in the organism. Eventually, a new species may evolve. Furthermore, certain members of a population with one group of variations may become adapted to the environment in one way, while others, with a different set of variations become adapted in a different way or become adapted to different environments. In this way two or more species may arise from a single ancestral stock.
The organisms always struggle to maintain their existence, as nature decides the survival of the fittest. Adaptive traits preserved through natural selection gradually bring changes in the characteristics of the species and thus evolution occurs.
Examples of Natural Selection
- The finches of Galapagos
The finches of Galapagos Islands provide an excellent example of natural selection. Some species of finches have short thick beaks. They are used to eating seeds, fruits and buds. Some others have long straight beaks. They subsist primarily on nectar from flowers. If environmental condition suddenly changes some characteristics may be more favoured than others.
- Industrial melanism in moth
The changes that occurred in the moth population in different areas of England are the best example for natural selection. Before Industrialisation, the tree trunks were lighter and light coloured moths were predominant. Dark coloured moths were also present but they were limited in number. As a result of industrialisation, the pollution resulted in the darkening of tree trunks. So the light coloured moths become more visible to birds and were therefore eaten by their predators. As a result of this at the end of 19th century the common light coloured moths were almost completely replaced by the black variety
Criticism of Darwinism
Several objections were made to the Darwin's theory:
- Darwin's explanation is inadequate because selection creates nothing, merely eliminates or preserves already existing variations without indicating their cause, which is the main question.
- Individual difference that may give rise to variations affect the reproductive cells little or not at all.
- A number of useless or non-adaptive characters or organs could not have arisen by natural selection. In this connection, Darwin said that we are no sure of the non-adaptive nature of these organs.
- Overspecialized organ such as the huge antlers of the Irish deer cannot be explained on the basis of natural selections.
- There is doubt about the struggle for existence being as fierce as it had been supposed to be.
- It cannot account for degeneracy of certain characters.
- The superiority or inferiority of one individual as compared to another of the same species is apparently not the result of the development of a particular characteristic, but rather of the general capacity of the organism.
The theory of origin of species by natural selection is regarded as a major advancement in evolutionary thought. Darwin contributed to the modern understanding of biological evolution by documenting the variation of living forms and identifying the key process of natural selection. Like most nineteenth century scientists, however, he did not understand heredity or how specific traits are passed from one generation to the next. His theory lacked the knowledge of modern genetics. However, mutation theory explained the causes of variations among organisms.
However, Darwin’s theory of evolution helped in removing all the conventional old beliefs which said that the formation of various species was a supernatural phenomenon or act of the Almighty. Darwin’s evolutionary theory of natural selection gave a more rational explanation with respect to the formation of new species.
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ABOUT CHARLES ROBERT DARWIN
Charles Robert Darwin (1809-1882) was a British biologist, born on 12th February 1809 in Shrew berg, England. He was nominated to the position of a young naturalist for the voyage on H.M.S. Beagle. It was in this ship; Charles Darwin sailed around the world. The voyage on the 'Beagle' started on 27th December 1831 and Darwin visited many Islands in Atlantic Ocean, some of the islands in the Pacific Ocean including Galapagos Islands, many places on the coasts of South America and finally returned after five years on 2nd October 1836.
During this voyage, Darwin took note of the flora, fauna, and the geology of the places visited. He also made extensive collections of living and fossil specimens of different species. He was writing his theory in 1858 when Alfred Russel Wallace sent him an essay which described. The same idea, prompting immediate joint publication of the theories of both of them. He presented his theory of evolution in the book On the Origin of Species by means of natural selection in 1859.