7.1 Neutral Evolution vs. Natural Selection

The neutral theory of evolution states that evolutionary changes at the molecular level are due to random genetic drift of selectively neutral nucleotide substitutions (Tong, Ranganathan, 2013). The mutations that occur under the neutral theory are the result of genetic drift. We can see these mutations become fixed over many, many generations. Although they are neutral mutations, they are able to be fixed due to genetic drift. Kimura's theory really differs from the original theory of natural selection due to the fact that Kimura's theory emphasized that these are random mutations. We also do not see much about fitness or environmental influences in Kimura's theory of neutral evolution. I believe that this basically contradicts the whole theory of evolution by natural selection, where the most fit individuals survive and reproduce as a result of having advantageous genes. The key differences are that Kimura's theory relies on random genetic mutations and lack of selection, whereas the theory of evolution by natural selection does not. 

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