Telling the Evolutionary Time: Molecular Clocks and the Fossil Record

Determining the precise timing for the evolutionary origin of groups of organisms has become increasingly important as scientists from diverse disciplines attempt to examine rates of anatomical or molecular evolution and correlate intrinsic biological events to extrinsic environmental events. Molecular clock analyses indicate that many major groups are twice as old, or more, than a literal reading of the fossil record attests, implying that the fossil record is incomplete. Few paleontologis...