The theory of Evolution as presented by Charles Darwin has had a great impact on the world today. It has caused many debates between religious authorities and those from the scientific community. This theory had prompted individuals to think about themselves, their origins and it has changed the way in which they view themselves in the environment. However, Darwin was not the first person to write on evolution. There were many others before him such as Lamarck, Buffon, and Darwin's grandfather Erasmus Darwin. However, what distinguishes Charles Darwin from the others is the fact that he collected and provided substantial proofs and he related various branches of science such as geology, botany and biology which helped validate his theories. His theory of natural selection as stated by Nelson and Jurmain (1991, p.606) in the modern form is that "the evolutionary factor causes changes in allele frequencies in populations due to differential net reproductive success of individuals." His grasp of the evolutionary process and the clarity of his work makes Charles Darwin the most popular figure in the scientific field of Evolution (Francoeur, 1965, p.34).
(1809-1882) was the fourth child of Dr. Robert Darwin and grandson of Erasmus Darwin. Much of Charles' childhood was spent collecting insects, coins and reading various literature on natural history,
having interest in poetry and philosophy was naturally inclined to study the work of his grandfather. Although Erasmus did not solve the problem of the process of evolution, the reading and exposure of his work made it easier for Charles Darwin to approach the topic and see it in a different perspective from Erasmus (Karp, 1968, p.17). In his early days at Cambridge University, Darwin was heavily interested in the works of William Paley (1743-1805) a famous theologist in his time. Paley's works which include Evidences of Christianity and Principles of Moral and Political Philosophy were required reading at the university. However, Darwin was most impressed by Natural Theology at the time. In this paper Paley examined the mechanism of the earth, its creatures, the complexity of their adaptations, their effective use of natural resources and their successful defence against nature. Paley also argued the inevitability of a Creator: "Design must have a designer. That designer must have been a person. That person is God" (Brent, 1981, p.274). As a student Darwin admired Paley and agreed with his philosophy. Paley had said that every species in existence was separately created by God. According to Paley nothing evolved. However, while Darwin was conducting research in evolution, he reread Paley's paper and discovering the flaw in it's logic proved it to be an important element in Darwin's reassurrance of the evolutionary process (Brent, 1981, p.306). Darwin disagreed with Paley on how species came to exist. Darwin argued that God had created species and through natural selection these species evolved over periods of time into the species that exist today. In the end Darwin used the power of the paper against itself in order to prove his theory of evolution. "Adaptation turned out not to be the result of some limitlessly benevolent design, but the very mechanism through which natural selection was expressed." (Brent, 1981, p.304). Darwin's rejection of Paley's ideology gave him a sense of pride and acted as a catalyst in his work on evolution. (Eiseley, 1961, p.178) Although Thomas Malthus was not a scientific writer like Erasmus Darwin and Charles Lyell, he had quite a strong influence on the intellectuals of his era due to the popularity and acceptance of his theories on population growth. One of these intellectuals was Charles Darwin. Thomas Malthus (1766-1834) was an English clergyman and political economist in the times of Darwin and his primary contribution to the economic world was the his theory of population which was published in Essay on the Principles of Population in 1798. According to Malthus, population tends to increase faster than the supply of goods available for its needs. Whenever there is relative gain in production over population growth, it stimulates a higher rate of population increase; on the other hand, if population grows too much faster than production, the growth is checked by famine, disease, and war. (Funk & Wagnall's New Encylopedia, 1979, p.438) Malthus' theory was seen as being a dismal expression of the human struggle for survival. This philosopy of survival of the fittest was used by many to prevent society from improving living conditions for the poor. For Charles Darwin, this theory provided an answer to the problem of evolutionary change through the process of natural selection. Darwin was impressed by Malthus' work and realized that the population theory could be applied to all aspects of organic life and provided a solid base in which natural selection could be studied. Darwin believed that the theories of biological variation combined with the struggle for existence explained the biological divergence found in organic life. Darwin had such strong beliefs in Malthus' theory that he used the population theory to help explain his own theory about natural selection in his book The Origin of Species (Darwin, 1859, p.13): In the next chapter the Struggle for Existence among all organic beings throughout the world, which inevitably follows from the high geometrical ratio of their increase, will be considered. This is a doctrine of Malthus applied to the whole animal and vegetable kingdoms. Since Malthus' theory was very popular and well accepted amongst the scholars of that era, Darwin used it so that his theory of natural selection would also be understood and accepted. Darwin had developed his theories before reading the works of Malthus, however his ideas were reinforced and this gave him the confidence to continue. Knowing that Malthus was popular and well received at the time, Darwin considered him a powerful ally who could assist him in presenting his theory of natural selection to the scientific world (Francoeur, 1965, p.53) . The geometric growth of life as expressed by Malthus greatly impressed him and may have turned his thoughts more intensively upon the struggle for existence. There is evidence in Darwin's essay of 1842 of his impressed reaction to the mathematical approach of Malthus. He comments almost as a memorandum to himself: "Study Malthus and calculate rates of increase [for various species]." (Eiseley, 1961, p.53) From the admiration and references Darwin gives to Malthus, it can be concluded that the ideas expressed by Malthus made him a key figure involved in Darwin's conclusions about evolution and natural selection. Sir Charles Lyell (1797-1875) was a British geologist born in Scotland. Although he studied law at the University of Oxford and was admitted to the bar, he followed a route that was completely different. He become a world renowned scientist famous for his studies and works in the field of geology. Both Charles Lyell and Charles Darwin were devoted believers of Uniformitarianism which established that "no forces had been active in the past history of the earth that are not also working today" (Nelson & Jurmain., 1991, p.36). The work that brought Charles Lyell acclaim was Principles of Geology . This was published when Lyell was virtually unknown as a geologist by his contemporaries (Chancellor, 1973, p.81). Lyell showed, through the process of uniformitarianism, that the earth's crust was formed via a series of slow and gradual changes.