The Neutral Theory, proposed by Motoo Kimura in the 1960s, suggests that most evolutionary changes at the molecular level are the result of random genetic drift rather than natural selection. This theory emphasizes that many mutations are neutral, meaning they do not significantly affect an organism's fitness. As a result, these neutral mutations can accumulate over time, leading to genetic diversity within populations. According to the Neutral Theory, the rate of molecular evolution is largely constant and can be measured by the number of neutral mutations that arise. This perspective contrasts with the traditional view that natural selection is the primary driver of evolutionary change, highlighting the role of chance in shaping genetic variation.