(I) An average individual experiences a lifetime of perhaps 70 years or so. (II) That person, through the memories of his or her parents and grandparents, may also indirectly experience earlier periods of time back over one or two generations. (III) The study of history gives one access - even less directly but often no less vividly - into hundreds of years of recorded time. (IV) This idea that something is older or younger relative to something else is the basis of relative dating. (V) But it is only archaeology that opens up the almost unimaginable vistas of thousands of years of past human existence.