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Evolution, Natural selection and Darwinism

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Introduction

Evolution, Natural selection and Darwinism Introduction Evolution refers to the processes that have transformed life on Earth from its earliest forms to the vast diversity that characterizes today. <Ref.1 - p414> Up until eighteenth century, biology in Europe and America was dominated by natural theology. <Ref.1 - p415> People believed that a supernatural being like God created each and every species as it is now for a particular purpose, at a particular time. However there are differences in people's interpretation of the length of the "day" mentioned in Genesis. Some Christians believe that the day was of 24hours and the world was created in 6 days. In 1650AD, Archbishop Ussher of Armagh calculated that God, created the world in October 4004BC, beginning on October the 1st and finishing with Man at 9:00am, which is not possible as we have no, archaeological evidence that suggest that a civilised life was already established in the Middle East by then. <Ref.2 - p879> Alternatively, there was the theory of spontaneous generation. A number of Greek philosophers believed in he gradual evolution of life. Amongst those philosophers, Plato (427BC-347BC) and Aristotle (384BC-322BC) influenced the western cultures the most. Plato believed in two worlds: a real world that is ideal and eternal, and illusory world of imperfection that perceive through our senses. He believed that the evolution would be counterproductive in a world where ideal organisms were already perfectly adapted to their environment. Aristotle, who opposed some of Plato's teachings being his student, believed too that the universe never had a beginning and would never end; it was eternal. <Ref.3 - Aristotle> He also believed that all living forms could be arranged on a scale. This is later called scala naturae (scale of nature), where the organisms could be arranged in the order of complexity. However with this view of life also, species are permanent, are perfect and do not evolve. ...read more.

Middle

3. Diversifying/Disruptive selection can result in balanced polymorphism. It favours variants of opposite extremes over intermediate individuals. In cases of microorganisms, they can evolve to build drug and pesticide resistance. As bacteria have only one loop of DNA, plasmid, its mutation would show directly and plasmids having transferred from one bacterium to another, would lead to formation of new species. <Ref.5 - p72> Darwin and Wallace independently developed the same theory of natural selection and they jointly presented their findings to the Linnaean Society in 1858. The essential features of the theory, which Darwin put forward, are: Observation 1: All species have such great fertility that their population size would increase exponentially if all individuals that are born reproduced successfully. Observation 2: Despite the tendency to fluctuate due to overproduction and season, most population actually remain stable in size. Inference 1: Production of more individuals than the environment can support leads to struggle for existence among individuals of a population, with only a fraction of offspring surviving each generation. Observation 4: Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike. Observation 5: Much of the variation is inheritable Inference 2: Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the surviving individual. Those individuals whose inherited characteristics best fit them to their environment are likely to leave more offspring than less-fit individuals. Inference 3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favourable characteristics accumulating over it's generations. The development of a number of variations in a particular direction over many generations will eventually lead to evolution of a new species. <Ref.1 - p420 & Ref.4 - p201> Darwin found the direct evidence that selection could lead to evolution in artificial selection. Humans have been modifying other species over many generations by selective individuals with desired traits as breeding stocks. ...read more.

Conclusion

- Use of simple tools and eventually manufacture of complex tools - Use of fire for cracking rocks, hardening wood, cooking food and defence against animals - Development of folk wisdom, art, religion, philosophy, science and technology Thus we see the basic biological needs of food, sex and safety were satisfied more efficiently by the development of group activities based on a common economic -political- sexual structure enriched and supported by the rapid development of culture. Indeed it can be said that current human evolution is based more on cultural development than on social behaviour. <Ref.2 - p 908> Art and religion Whilst humans share many aspects of behaviour with other primates and non-primates, there are some, which are unique to the species, and these include art, religion and free will. The earliest examples of representations of animals and humans come from the Upper Palaeolithic (3000 years ago). Some are carved in wood or ivory and some are carved on cave walls. The significance of this early art is not known, but we do know that such activities require tolls, skill, observation, thought, motivation and possibly leisure. In some cases the art forms depicted animals and sex and these were often associated with death and birth respectively. Whether they had religious significance is not clear, but current opinion suggests they were not associated with religious figures, as we know them today. Religion is believed to have developed at about the same time as cave painting as evidence by the forms of burials found in various parts of the world. In many cases, the dead were buried along with offerings such as food, tools, and decorative ornaments. It is believed that this symbolism indicates established religious practices. Such a development requires the involvement of conscious intelligent thought, one of the most sophisticated aspects of cultural development. Religion as it is perceived today is fairly recent, the earliest shrines and temples and their accompanying artefacts being less than 10000years old. <Ref.2 -p908> ?? ?? ?? ?? ...read more.

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