Free The New Penguin History of the World by Odd Arne Westad, J. M. Roberts Page A

metal artifacts date from about 4000 BC and are beaten copper pins found in Egypt. Once the technique of blending copper with tin to produce bronze was discovered, a metal was available which was both relatively easy to cast and retained a much better cutting edge. It was in use in Mesopotamia soon after 3000 BC . On bronze much was to be built; from it, too, much derived, among other results the quite new importance of ore-bearing areas. In its turn, this was to give a new twist to trade, to markets and to routes. Still further complications, of course, followed the coming of iron, which appeared after some cultures had indisputably evolved into civilizations – another reflection of the way in which the historical and prehistoric eras run so untidily into one another. Its obvious military value springs to the eye, but it had just as much importance when turned into agricultural tools. This is looking a long way ahead, but it made possible a huge extension of living space and food-producing soil: however successfully he burned woodland and scrub, Neolithic man could only use a stone adze or scratch at heavy soils with an antler or wooden pick. Turning them over and digging deep began to be possible only when the invention of ploughing (in the Near East in about 3000 BC ) brought animal muscle-power to the assistance of humans, and when iron tools became common.
    It is already clear how quickly – the term is legitimate against the background of earlier prehistory even if it takes thousands of years in some places – interpenetration and interplay begin to influence the pace and direction of change. Long before these processes have exhausted their effects in some areas, too, the first civilizations are in being. Prehistorians used to argue whether innovations were diffused from a single source or appeared spontaneously and independently in different places, but so complex a background has made this seem a waste of time and energy. Both views, if put forward in an unqualified way, seem untenable. To say that in one place, and in one place only, all the conditions for the appearance of new phenomena existed and that these were then simply diffused elsewhere is as implausible as saying that in widely differing circumstances of geography, climate and cultural inheritance exactly the same inventions could be thrown up, as it were, time and time again. What we can observe is a concentration of factors in the Near East which made it at one crucialmoment immeasurably the most evident, active and important centre of new developments. It does not mean that similar individual developments may not have occurred elsewhere: pottery, it seems, was first produced in Japan in about 10,000 BC , and agriculture evolved in America perhaps as early as 5000 BC in complete isolation from the Old World.
    This means that human prehistory comes to an end in a ragged, untidy way; once again, there is no neat dividing line from history. At the end of prehistory and on the eve of the first civilizations we confront a world of human societies more differentiated than ever before and more successful than ever in mastering different environments and surviving. Some will continue into history. It is only within the last century or so that the Ainus of northern Japan have disappeared, taking with them a life that is said to have been very similar to one they lived fifteen thousand years ago. Englishmen and Frenchmen who went to North America in the sixteenth century AD found hunter-gatherers there who must have lived much as their own ancestors had done ten thousand years before. Plato and Aristotle were to live and die before prehistory in America gave way to the appearance of the great Maya civilization of Yucatán, and prehistory lasted for Eskimos and Australian aborigines until the nineteenth century.
    No crude divisions of chronology, therefore, will help in unravelling so interwoven a pattern. But its most important feature is clear enough: by 6000