An important part of archaeological research is the dating of artefacts and structures that are found in the field. In the nineteenth century prehistoric periods were determined based on cultural aspects and these cultures were identified by the characteristics of artefacts, mostly tools and pottery. The Stone Age is thus characterized by stone tools and subdivided in old, middle and new stone age; Paleolithic, Mesolithic and Neolithic. Following the Stone age the periods have been determined based on the type of metal; copper, bronze and iron. It is a common supposition that in every period there was technological progress, therefore the paleolithic tools are considered coarser while those of the Neolithic are much finer and more elaborate, in fact the arrowheads, knives and scrapers are called microliths, small stone artefacts made of obsidian and flint. The use of metal depended much on the technology of melting and working the materials. It is not suprising that with the use of iron in the Iron Age cremation became the predominant burial practice, as both require the fire to reach certain temperatures which could be attained with the technological progress of more efficient furnaces.
With the invention and spreading of writing the historical period began. This occurred first mainly in Egypt, Greece and the Roman empire. The area's where writing was not widely used, but where Egyptians, Greeks and Romans wrote about the people around them is considered the protohistory, the period preceding the historical age. For example the presence of Phoenicians and Punics on Sardinia is considered protohistory, Greek and Roman historians wrote about it but we do not have direct written sources, other than a number of Phoenician and Punic inscriptions. That is in itself not suprising because the Romans destroyed with Carthage almost everything the Punics had produced in writing.