GED Science: Charles Darwin and The Mechanism of Evolution

Charles Darwin was the first to formulate a scientific argument for the theory of evolution by means of natural selection. Charles Robert Darwin was born on 12 February 1809 in Shrewsbury, Shropshire into a wealthy and well-connected family. His maternal grandfather was china manufacturer Josiah Wedgwood, while his paternal grandfather was Erasmus Darwin, one of the leading intellectuals of 18th century England.

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Darwin himself initially planned to follow a medical career, but did not enjoy it. Rather, he had always had an interest in nature, and so in 1831, soon after finishing college, he joined a five year scientific expedition on a ship called the HMS Beagle.

On the voyage, Darwin read a book called ‘Principles of Geology’, by Charles Lyell, which suggested that the fossils found in rocks were actually evidence of animals that had lived many thousands or millions of years ago. Lyell’s argument was reinforced in Darwin’s own mind by the rich variety of animal life and the geological features he saw during his voyage. The breakthrough in his ideas came in the Galapagos Islands, 500 miles west of South America. Darwin noticed that each island supported its own form of finch which were closely related but differed in important ways.

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In the diagram above, you can see that there are subtle differences in the beaks of the finches, depending on the food source of the finch.  Finches that probe for insects tend to have longer, sharper bills, for example.

On his return to England in 1836, Darwin tried to solve the riddles of these observations.  Influenced by the ideas of Thomas Malthus (an economist who published essays on how populations are limited by factors such as famine and disease), he proposed a theory of evolution occurring by the process of natural selection. The animals (or plants) best suited to their environment are more likely to survive and reproduce, passing on the characteristics which helped them survive to their offspring. Gradually, the species changes over time.

Darwin worked on his theory for 20 years. After learning that another naturalist, Alfred Russel Wallace, had developed similar ideas, the two decided to made a joint announcement of their discovery in 1858. In 1859 Darwin published a famous book called ‘On the Origin of Species by Means of Natural Selection’.

The book was extremely controversial, particularly because Darwin’s theory of evolution by natural selection, if applied to humans, indicated that human beings were simply another form of animal that had evolved from an ancestral species – quite possibly some kind of monkey or ape-like species, which many people found very difficult to accept. Furthermore, at this time, most Europeans believed that the world was created by a supernatural being in seven days, as described in the bible. Darwin’s theory posed a significantly different idea about how the world was created. Darwin endured a significant amount of controversy, but the strength of his theory, with its clear explanation and many pieces of supporting evidence, continued to gain acceptance. By the early 20th century, Darwin’s theory of evolution by natural selection become the generally accepted theory for how populations change over time.

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