Preface

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Welcome to the neutrality world!

It is necessary to clarify the meaning of the term "neutrality". One interpretation of neutrality, widely known as neutral mutation hypothesis due to Motoo Kimura, is that the majority of mutations that have contributed significantly to the genetic variation in natural populations are neutral or nearly neutral. Although highly influential, the neutral mutation hypothesis is not sufficiently quantified to be tested rigorously. A more narrower definition of neutrality is that all mutations (at a locus) are selective neutral, which is referred as the hypothesis of strict neutrality. All the tests here test essentially the hypothesis of strict neutrality. Since the hypothesis of strict neutrality is narrower than the neutral mutation hypothesis, it is important to emphasize that a rejection of the former does not necessarily falsify the latter because a few mutations subject to strong natural selection can lead to the rejection of strict neutrality while majority of mutations are neutral or nearly neutral.