Motoo Kimura developed this theory in the 60-70's to explain the high level of molecular diversity observed in populations, stipulating that the majority of mutations were neutral or nearly neutral, but without eliminating the role of natural selection. This theory has been somewhat marginalized in the past two decades. However, it is a fundamental theory that can explain many evolutionary changes. It is also the base of the molecular clock theory used by many researchers for their phylogenetic reconstructions.
Forty years after Kimura, and given the dramatic developments in molecular genetics and evidence of selection in many genes, where do we stand?