Molecular clock hypothesis

The Molecular Clock Hypothesis, postulated in 1965 by Emile Zuckerkandl and Linus Pauling, asserts that the rate of evolutionary change of any specified protein was approximately constant over time and over different lineages. It has been applied to DNA sequence evolution also, particularly neutral evolution. Subsequent testing has shown that, while the MCH canot be blindly assumed to be true, it does hold in many cases, and these can be tested for. Knowledge of approximately-constant rate of molecular evolution in particular sets of lineages facilitates establishing the dates of phylogenetic events.