The all-important achievement of this period was unquestionably the dawn of literate societies. There was a convergence of social, religious, technological and economic advances creating true city life and various kinds of centralized government. Although substantial towns developed in some of the early centres of mixed farming, it was only in the last two or three centuries of the fourth millennium, and only in Mesopotamia and Egypt, that the changes were revolutionary enough to represent a difference in kind from anything that had gone before. Sumeria led the way in the development of cities literacy, but Egypt raced away under the powerful central government of its divine rulers of the First Dynasty. This period therefore closes with the peoples of both the great river valleys having rich urban cultures although with very different social and political forms. In both civilizations, their societies were shaped and coloured by a totally religious views of life and the cosmos.

Other historical events of this time were in large part an extension of those of the previous period: the further spread of farming to western and northern Europe and eastward to parts of India and China.

In Europe some of the peoples now reached by the Neolithic Revolution came to use their increasing numbers and social organization to create a crude yet monumental form of architecture - large stone, or megalithic, tombs. The oldest of these tombs were being built from 4500 BC, when temple-centred towns were springing up in Sumeria. The building of megaliths spread and reached its climax only towards the end of the fourth millennium, contemporary with the unification of Egypt and the rule of the first human being known by name. This was also the time when the very earliest, and still architecturally primitive, temples were under construction in Malta.

The rapid progress towards urban civilization inevitably involved appropriate technological advance. In the previous period inventions had been of a domestic kind, of advantage to the home life of farmers. Now they were associated mainly with transport, communication and more organized trade, or with increasing production for relatively large populations concentrated in towns.

Over the progressive regions of Eurasia this period roughly coincides with the Copper Age, sometimes known as Chalcolithic to emphasize the fact that stone remained in use for many implements. It is not a very well- defined period, yet the name calls attention to the growth of large- scale metallurgy which wass to be of the most important of civilized skills and at the same time a great stimulus to trade. In the fifth millennium, the smelting of ores became common and axes and blades of some size were cast in open moulds.

The settlers of the Mesopotamian valley, particularly the Halafians in the north, brought some knowledge of copper working with them and would have maintained contacts with the mountain zones for ore supplies. Probably the evolution of the smelting process was connected with the development of improved kilns for firing fine painted pottery and, more generally, with a new knowledge of the control and purposeful use of heat. By the end of the millennium there must have been a class of specialist coppersmiths engaged in satisfying a widespread consumer market for a range of metal objects.

In technology the most important advance of the time was the discovery of alloying - by adding tin to copper the harder, more manageable bronze could be produced. The right proportions were discovered and there was rapid advance in both smelting and casting. In progressive areas outside the river valleys, eastward to India and westward to Greece, this millennium roughly coincides with the Early Bronze Age. Further to the west and north a true Bronze Age was not to begin until about 2000 BC, the Chalcolithic or even Neolithic technologies lingering on.

What was achieved by the Sumarians and Egyptians during this millennium represents in many ways the height of the Bronze Age world. By 2500 BC a third powerful, though less creative, civilization had arisen in the Indus valley. However, it was in the Mediterranean, and particularly in the lands round the Aegean, that the third millennium was a time of new cultural developments. Here from Troy and the offshore islands, through the Cyclades, thriving from maritime ventures to Early Minoan Crete, there were already signs of the first European high civilization was to have its fulfilment after 2000 BC.

Intellectual innovations were innumerable: Sumeria's scribal colleges were probably first in the production of poetic literature, scholarship and elementary mathematics, but Egypt had her pyramid texts and abstruse theological literature. The Egyptians also seem to have been first with one practical intellectual achievement: the establishment of a calendar as early as 3000 BC. The Indus people devised their own script, but it was used mainly on their beautiful seals and probably remained primitive.

If the Sumerians led in literature, the Egyptians were supreme in the visual arts and architecture. The truly amazing growth of an elegant monumental architecture in masoned stone, as well as the pyramid from 2700-2500 BC is not even approached by the ziggurat temples of Sumeria, remarkable though these were. The local Maltese temple architecture, relatively small in scalc, was probably at its height at much the same time. Indus architecture tended to be severe and functional and megalithic building in western and northern Europe continued but without new inspiration.

The most significant technical invention of this present period was the production of carbonized iron. This difficult technique was first perfected by the Hittites about the middle of the millennium, but they guarded it as a vital military secret, and it was only after their fall in the late thirteenth century that their smiths seem to have been dispersed and the new, more plentiful metal was generally adopted in the Near East and eastern Mediterranean. In Egypt it was hardly in use before l000 BC and it took several more centuries for blacksmithing to reach western Europe.

As might be expected for an age of great power rivalry, some of the most important technical advances of the second millennium were in instruments of war The light battle chariot with its pair of spoked wheels provided a fast-moving mount from which the warriors could shoot arrows and hurl spears. Used for concerted charges, the chariotry revolutionized the conduct of pitched battles such as Megiddo and Lagash. With it went the smaller, more powerful composite bow, which intensified fire power. Another new weapon of even more lasting importance was the sword, probably invented in central Europe and widely adopted from the sixteenth century BC.

If iron was the most lastingly important of material inventions, alphabetic writing was more than its equal as an intellectual advance. It was probably with the seventeenth century BC that the Hittites adapted cuneiform to their Indo-European language, while the Minoans of the Old Palaces from the first used a pictographic script, developing the more efficient Linear A in time for it to be used throughout the island in New Palace times. The early Greek of the Mycenaeans was written in Linear B both on the mainland and in Crete from the fifteenth century. At much the same time the Chinese Shang were employing a script ancestral to the historic form.

Like the Mesopotamian and Egyptian writing of the third millennium these scripts were no more than partially phonetic with sounds based on syllables and a vast range of qualifying signs. They were both immensely laborious and inefficient. To invent a system based on a sign for every sound required genius - and probably also courage against the vested interest of the scribes. For just as iron was to put good tools into the hands of the common man, so the alphabet put writing within the reach of merchants and traders.

The Bronze Age world of the near East had entered the second millennium at a time when cultures began to merge.  There had been a great incursion of barbarians and Semitic nomads in the last centuries of the previous millennium. These incursions continued and there was further expansion of the Indo- European peoples.  This millennium also saw the rise and fall of the Hittites and the Hurrians and the Assyrians' first spasmodic successes at building an empire.

An outstanding development was the first attainment of high civilization in Europe - that of the Minoans in Crete. Their palaces and administrative records kept on clay tablets show how much they owed to the orient, yet the whole style and spirit of Minoan life and arts was quite different from the pomp and circumstance of the great river valleys.

The civilization created during the previous three thousand years in Mesopotamia and Egypt were maintained and in many ways they reached the height of their power and intemational influence.  However along with this climax and decline of the Bronze Age came the first rise of Greeks and Hebrews.

Equally important for future cultural change was the sudden emergence of the bronze- using culture of the Shang Dynasty.  This emerged from the ancient New Stone Age of northern China.  In the Americas the first ceremonial centres and monumental sculpture appeared among the Olmecs of Mexico.