The constant divergence rate of protein sequences is the rule for virtually all proteins and taxa that have been examined. A phenomenon this universal demands some sort of general evolutionary explanation. The Neutralist View. The Neutralist view maintains that most protein evolution is due to genetic drift. Most mutations are deleterious, and are therefore eliminated by natural selection as soon as they occur.
Some mutations have negligible effect on fitness, and are therefore effectively neutral.
A small but real fraction of these mutations will be fixed by genetic drift and thus cause evolutionary change in protein sequence. This fixation of effectively neutral alleles by drift accounts for most protein evolution. The Selectionist View 1. The Selectionist view maintains that most protein evolution is due to natural selection. Most mutations are deleterious, and are therefore eliminated by natural selection as soon as they occur.