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Ideas about evolution
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Ideas – including scientific ones – occur in different places, with different people and at different times. And no new theory emerges from a vacuum of ideas, but rather takes shape from various sources. Many people in the past had put forward the idea of evolution. Aristotle (384-322BC) classified animals and arranged them in a series of increasing complexity. Bishop Ussher in 1650 had calculated that – according to Bible – the Earth was created in 4004BC, which made it about 6000 years old. This time was far too shot for evolution to have occurred. Now the Earth is thought to be 4,6 billion years old.
The grandfather of Charles Darwin – Erasmus Darwin (1731-1802)– put forward his own theory of evolution. He believed that God had created the first simple organisms. These organisms evolved into new species. By this time a study of the Earth`s surface was beginning to show that it had its origins hundreds of millions of years ago.
Lamarck (1744-1829) proposed an interesting theory of "Transformism". He suggested that animals have an innate tendency to increase in size and complexity. He also pointed out that different environments made different demands on the individuals which then evolved to meet these needs. Lamarck`s theory suggested that due to environmental pressures certain organs would be used more ( or less) than others. For example a mole`s eyes were diminished in size and function through disuse in the underground habitat. For this kind of evolution to work it is essential for each modification to be passed on to the offspring. And with each new generation the modification becomes more pronounced. This belief in the inheritance of acquired characteristics persisted until the 1900s.
There were two schools of thought about evolution in general. Geological studies showed that the Earth`s crust was made up of distinct layers of rock , with different fossils in each layer. Believers in catastrophism thought that this represented a series of world wide disasters in which living organisms were wiped out and new forms created.
Uniformitarians, on the other hand, thought that the forces which shaped the Earth`s crust in the past were no different from those in action today, e.g. mountain building, erosion, volcanic activity, and that they formed a continuous process.
Charles Darwin (1809-1882) combined his own experience as a breeder ( he bred pigeons), his observations as a naturalist and ideas of other scientists and philosophers into a new theory. He assumed that the better adapted varieties would be "selected" by pressure of the environment. Darwin also was sure that these "selected variations" should be heritable. But he didn`t knew how these variations were passed on to the offsprings.
Alfred Russel Wallace (1823-1913) made a career of a naturalist which was very similar to Darwin`s. He made a voyage to the Amazon basin, Malaysia and the East Indies. Wallace, like Darwin, had read Thomas Malthus and formulated a theory of natural selection. They published jointly in 1858.
Darwin`s book was widely read but his theory of natural selection was opposed by many members of the scientific world and is not accepted by some religious groups even today. The theory was clinched only in the 1900s, when Mendel`s papers were re-discovered. It was then realized that mutations were the principal source of Darwin`s "variations" and genetics could explain how they were inherited.
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