Molecular Evolution Activities

The Molecular Clock

The Molecular Clock

What is the molecular clock?

A molecular clock is not like a mechanical time piece. It is a stochastic clock. Individual "clicks'' of the clock will not occur with perfect time periods separating them, but enough "clicks'' of the clock should have an expectation that is constant. The clock is sloppy. The question is: how sloppy can it be and still be considered a clock? This is the Problem of Variability.

There are two reasons for being interested in the molecular clock:

(1) The clock can help establish a time scale for evolution.

(2) The clock has important implications for our understanding of the mechanisms of molecular evolution.

The relationships between the molecular clock and timescales and mechanisms have both been controversial.

The reliability of the molecular clock as a means of estimating evolutionary timescales has been called into question in a numerous specific cases. See Slowdowns and Speedups for more.

Very soon after the molecular clock was introduced, a neutralist mechanism was proposed. For more on the clock and its putative mechanisms see the Neutralist Mechanism.



The Molecular Clock


This page was last updated on 1 August 2002 by Michael Dietrich.