A significant key to the development of civilisation was the use of metals, skills that took millennia to develop. The first experiments with copper took place in Anatolia from around 7,000 BC and by 5,000 BC gold and copper objects were being manufactured in the Balkans. The earliest bronze casts were made around 4,000 BC in Asia Minor and it took at least another thousand years before the spread of the technology was significant enough for us to define the Bronze Age.
The true secret of the Bronze Age achievement was efficient agriculture that created a surplus of food over the basic needs of the farmers. This was the beginning of ‘growth’ that drives economic development today. Some of this extra food could then be exchanged for specialised skills and crafts such as pottery and tool making. Rather than living just for themselves and their immediate families, people were able to live in communities, helping and becoming more dependent upon each other. Denser populations became possible and people concentrated around centres of trade, a royal court or a temple. These concentrations were embryo cities that increased the intensity and variety of communication, and the exchange of ideas stimulated further invention.
In the Western Civilisation, the first recognised Bronze Age Society was that of the Sumer in Mesopotamia between about 3,500 and 3,000 BC. This early progress in metallurgy allowed improvements to methods of irrigation and shipbuilding and hence to better agriculture and transportation. . Two other centres of civilisation developed about the same time in the valleys of the Indus in northwest India and the Nile in Egypt. Whether these civilisations were in contact or not is uncertain. Modern consensus has it that they probably were.
Recent research  has raised the possibility of an entirely new version of the history following the retreat of the ice sheets of the northern hemisphere. Evidence is produced for an earlier highly developed civilisation in the lands of Egypt around at least 9,000 BC, a date that is now ascribed to the building of the Sphinx. This civilisation is thought to have been expert in astronavigation, which itself implies long experience and knowledge of sea travel. It is proposed  that this as yet unidentified civilisation spread around the world, giving rise to the Aztec and Inca civilisations of South America and the civilisation responsible for the building of the fabulous temples of Angkor Wat in Cambodia. It could be that the spread was even wider and it may be linked to the theories of Heyerdahl  proposed from the late 1940s onwards. During the course of his earliest expeditions, Heyerdahl demonstrated how the population of the remote Pacific islands occurred when emigrants escaping the punitive culture of the Aztecs set off from South America on rafts around 600 AD and were carried there by wind and tide. He later showed how, similarly, it was possible for emigrants from North Africa to achieve similar epic journeys across the Atlantic Ocean on rafts constructed from papyrus reed materials. The logical projection of this thesis formed by other writers is that this emigration resulted in the creation of the Aztec and Inca civilisations of South America and would have taken place much earlier, although precisely when is speculative.
The melting of the vast northern ice sheets around 10,000 BC created an increase in sea level that, in turn, had serious impact on civilisations. This global increase in sea level was followed many millennia later by other smaller changes to sea level, notably a fall of about 1 m in the Mediterranean during the lifetime of the city of Troy (see below). The cultures inhabiting the lands of northwestern India saw their coastal-based cities submerged beneath the encroaching sea of the post Ice Age era. Their lands were vastly reduced in size; in some cases their cultures may not have survived at all. Indeed, recent underwater research has shown much evidence of early civilisations occupying what was then coastal land, but became submerged by the rise in sea level at a number of other sites in India. The Mediterranean too was affected, and islands such as Sicily and Malta also show evidence of peoples with well-developed cultures living on land that is now below sea level. This theory lends far more credibility to the famous story about the lost civilisation of Atlantis, for it is likely that the rise in level of the Atlantic Ocean also submerged areas of land off the coast of West Africa in the region of the Canaries or the Azores. These theories are still very new and little more can be added at this point, especially in regard to the role of navigation amongst these peoples. We can say that these ancient peoples must have lived in the Early Stone Age, and because of the limitations to shipbuilding without the benefit of metal tools and nails it is very unlikely that there was sufficient activity on the sea to warrant the construction of lightstructures.
We are thus inclined to focus our attention on the period from 3,000 BC onwards - the beginning of the Bronze Age when metallic tools became available. To investigate matters further we need to consider aspects of the history of some better-known early cultures. The obvious candidates to investigate are the Egyptians, the Romans, the Phoenicians and the Greeks.