Prompt 7

To understand the similarities and the differences between the two theories of evolution, let us first do a refresher on what Motoo Kimura's neutral theory of evolution proposed. The neutral theory proposes that evolutionary changes within species is not caused by natural selection alone. Instead, the driving factor is by genetic drift instead. As a result, mutant genes that arrive are determined by random genetic drift. This theory is not saying all variation is selectively neutral, rather, it is saying that a large portion of mutations are deleterious and would be removed from the population. However, some new adaptive mutations are able to make it, while all the remaining mutations are selectively equivalent (neutral), and their fate is determined by genetic drift. So, the variation we see within and between species are not thought to have effect on the fitness of an organism. We all pretty well know the theory of natural selection, so I'll be succinct. It's the process in which individuals with a certain trait tend to have more offspring in the next generation than individuals with different traits.

So how does this come into play when comparing neutral theory and the theory of natural selection? Within the span of generation, mutants can appear in a population, but many are lost to chance. However, a few mutations are able to make it through the gauntlet and are lucky enough to fix. Kimura and Darwin's theory do not differ in the end result when it comes to this outcome. Both theories allow for this role to occur, but what differs is the chance of the mechanism. Neutral theory takes a more molecular approach. For neutral theory, this process is one that is occurring by chance. In contrast, under the theory of natural selection, selection is playing a much larger role. Selection allows mutants that are advantageous to fix in the population instead.


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