Darwin's view of change being mostly driven by traits that provide advantage was widely accepted until the 1960s. While researching mutations that produce nucleotide substitutions in 1968, Motoo Kimura found that the rate of substitution was so high that if each mutation improved fitness, the gap between the most fit and typical genotype would be implausibly large.
Darwin's theory of evolution being primarily driven by traits that offer a benefit was widely accepted until the 1960s. Through his research into mutations resulting in nucleotide substitutions in 1968, Motoo Kimura found that the rate of substitution was extremely high, rendering it implausible that each mutation would improve fitness, and thus creating an unacceptably large disparity between the fittest and typical genotype.