Fig. 1.

Darwin postulated the existence of deleterious, advantageous, and neutral changes. The neo-Darwinians (or selectionists) neglected neutral changes. These were reintroduced and amplified by Kimura (7, 8), who developed the neutral theory of evolution (a non-Darwinian evolution, according to ref. 9). The nearly neutral theory was proposed by Ohta (12, 13, 102) to include intermediates between neutral and advantageous, as well as between neutral and deleterious changes. In the neoselectionist theory, the critical changes are responsible for the transition from point mutations to regional changes (modified from refs. 12 and 103).