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 perspective on evolution being primarily driven by characteristics that offer an advantage was widely accepted until the 1960s. During his research into mutations resulting in nucleotide substitutions in 1968, Motoo Kimura discovered that the rate of substitution was extremely high, rendering it implausible that each mutation would improve fitness, leading to an unacceptably large gap between the fittest and typical genotype.