A theory according to which the majority of the nucleotide substitutions in the course of evolution are the result of the random fixation of neutral or nearly neutral mutations, rather than the result of positive Darwinian selection. Many protein polymorphisms are selectively neutral and are main tained in a population by the balance between mutational input and random extinction. Neutral mutations are not functionless; they are simply equally effective to the ancestral alleles in promoting the survival and reproduction of the organisms that carry them. However, such neutral mutations can spread in a population purely by chance because only a relatively small number of gametes are “sampled” from the vast supply produced in each generation and therefore are represented in the individuals of the next generation. See Chronology, 1968, Kimura.
Subjects: Genetics and Genomics.