Archaeological investigation of the material remains of prehistoric Man has shown that a wide variety of cultures flourished in different parts of the world and at different times. For convenience these have been grouped into a series of major cultures based primarily on the nature of the principal material used for implements (whether stone or one of the metals), and sometimes on the technique used in fashioning these implements. The oldest culture in the world was characterized by the use of chipped stone for implements and has been named Palaeolithic culture. Neolithic culture, on the other hand, was characterized by the use of polished stone implements; Bronze culture, by the use of bronze implements, and so forth.
In most parts of the world the discovery and use of these different materials and techniques took place in a regular sequence in time. In the absence of fixed dates, it was thus found convenient to use these cultural terms in a chronological sense. Accordingly prehistoric times have usually been divided into the following series of periods or ages (beginning with the oldest) Palaeolithic (Old Stone), characterized by chipped stone implements; Mesolithic (Intermediate Stone), a transitional period; Neolithic (New Stone), with polished stone implements; Chalcolithic (Stone and Copper), characterized by the first tentative use of copper implements; Bronze Age, with full development of copper and bronze implements; and Iron Age, with iron implements.
These names are excellent to identify cultures, but their use to designate periods of time has led to much inaccuracy and confusion, as the dates of the cultures to which they refer differ widely in different parts of the world. It is proper, for example, to speak of the Bronze Age of Hungary or some other limited area, where the beginning and end of the bronze culture can be fairly accurately dated. But it is quite impossible to speak with any meaning of the Bronze Age of the Old World, for this period began some thousand or fifteen hundred years earlier in Mesopotamia, for instance, than it did in western Europe, and it gave way to the Iron Age one or two thousand years earlier in Asia Minor than it did in some parts of Siberia; while in Japan there was no true Bronze Age and in Australia no Bronze Age at all. The names of these periods are, however, too well established to be abandoned and are often useful, if employed with caution.