The Current Status of the Neutral Theory of Molecular Evolution
Prof. Naoyuki Takahata
Ever since its proposal, the Kimura’s neutral theory of molecular evolution has been a subject of great controversy. After four decades of heated debates, Crow expressed his view about the status of the theory: “It is the natural null hypothesis for studies of selection and is increasingly used for this purpose. … It is doubtful whether the neutral theory is as important and widespread as Kimura thought. Yet, for noncoding DNA, synonymous changes, and such there is reason to expect neutrality. I think a reasonable summary is that most of the DNA in vertebrates is evolving neutrally. In contrast, the amount of neutrality for proteins is more in doubt.”
During the last decade, there has been a dramatic increase in the study of identifying genomic regions under positive and negative selection. In this talk, I first summarize the essence of the neutral theory and overview recent results on genomic regions under selection along the human lineage. Since some genome-wide scans identify a large number of amino acid and gene substitutions along the human lineage, I revisit the concept of the cost of natural selection/the substitutional load that limits the rate of evolution. I also touch upon the mutational load owing to the deleterious mutations in the human genome. Some theoretical and simulation results on these genetic loads are presented to make my argument quantitative.
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