Complex sentence: The neutral theory of molecular evolution is an influential theory, introduced with provocative effect by Motoo Kimura in the late 1960s and early 1970s, which states that the vast majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants.
Split into simpler sentences: The neutral theory of molecular evolution is an influential theory, which was introduced with effect by Motoo Kimura in the late 1960s and early 1970s. The theory states that the vast majority of evolutionary changes at the molecular level are caused by random drift of selectively neutral mutants.