Lines of evidence: The science of evolution :
Distribution in time and space
Understanding the history of life on Earth requires a grasp of the depth of time and breadth of space. We must keep in mind that the time involved is vast compared to a human lifetime and the space necessary for this to occur includes all the water and land surfaces of the world. Establishing chronologies, both relative and absolute, and geographic change over time are essential for viewing the motion picture that is the history of life on Earth.