Explaining evolution 6: Darwin’s theory of evolution


The 6th blog in our GCSE Science series Explaining evolution looks at Darwin’s work.

Explaining evolution 6 – Darwin’s theory of evolution

In the previous blogs I referred to current scientific understanding that explains evolution through evidence from fossils, extremely long time scales and species development by random mutation. In the 19th century this understanding of science was in its infancy and creation by a supernatural being was the accepted explanation for the existence of abundant and varied life on earth.

Charles Darwin studied biology in the mid 19th century and, as a result of travelling around the world and extensive personal research, began to appreciate that random mutations, long time scales and changing natural environments could explain how the variety of life had come about, rather than it being created. He began to use the term ‘natural selection’ to describe how species change and referred to the continuing development of life as ‘evolution’.

Darwin was meticulous in his research but not the only scientist following the evolutionary idea. When informed that Alfred Wallace was on the point of publishing a similar idea, Darwin published a book titled ‘On the Origin of Species’. In this book he proposed that species develop because small, positive, random mutations, which continually appear in species over thousands of generations, produce individuals that are better equipped to survive, thrive and breed in their environments, such that each progressive mutation becomes part of the norm. This explanation is called ‘natural selection’.

Darwin used the development of species to explain why there are different species. He proposed that random mutations in changing environments cause so many changes between groups of the same living organisms that eventually a new species of the organism is formed. A famous example of this is Darwin’s finches (see Explaining evolution 9 – Darwin’s finches).

Darwin further explained that life had ‘evolved’ on Earth over an extremely long time. All life had a position on a ‘tree’ of life and ultimately all living organisms had descended from common ancestors that had lived many, many years ago.

It is true to say that ‘On the Origin of Species’ is one of the most important scientific books ever published, not only for the concept of evolution (which caused much controversy in the 19 century), but also because its ideas were supported by meticulous scientific research, observation and detailed illustration. The book represented Darwin’s theory of evolution and the phrase ‘survival of the fittest’ was used to summarise the theory (see the next blog Explaining evolution 7 – Survival of the fittest).

John Roach

Tutor

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