66. Stone and Metals
The cultural record of man’s existence is divided into two great periods. In the latter of these, in which we are still living, metals were used; in the earlier, metals were unknown and tools made of stone. Hence the terms “Age of Stone” and “Age of Metals.” The duration of these two main periods is unequal. Metals were first used in Asia and Egypt about 4,000 B.C. and in Europe about 3,000 B.C.—say five to six thousand years ago. The most conservative authorities, however, would allow forty or fifty thousand years for the Stone Age; while others make it cover a quarter million. The assumption, which is here followed, of the intermediate figure of a hundred thousand years gives the Stone Age a duration twenty times as long as the Age of Metals. When one remembers that hand in hand with metals came the art of writing and an infinite variety of inventions, it is clear that larger additions have been made to human civilization in the comparatively brief period of metals than in the tremendously longer time that preceded it. Progress in the Stone Age was not only slow, but the farther back one peers into this age, the more lagging does the evolution of human culture seem to have been. One can definitely recognize a tendency toward the acceleration of evolution: the farther advancement has got the faster it moves.
The Age of Metals is subdivided into the Iron Age, which begins some three thousand years ago, say about 1,500-1,000 B.C.; and an earlier Bronze Age. In the Bronze Age one must distinguish first a period in which native copper was employed in some parts of the world; after which comes an era in which it had been learned that copper melted with a proportion of about one-tenth tin, thus producing bronze, was a superior material. Within the past five thousand years or so, accordingly, there are recognized successively the ages of copper, of bronze, and of iron.
Broadly speaking, these five thousand years are also the historic period. Not that there exist historic records going back so far as this for every people. But the earliest preserved documents that the historian uses, the written monuments of Egypt and Babylonia, are about five thousand years old. The Age of Metals thus corresponds approximately with the period of History; the Stone Age, with Prehistory.