The European Chalcolithic, the Chalcolithic (also Eneolithic, Copper Age) period of Prehistoric Europe, lasted roughly from 5000 to 2000 BC, developing from the preceding Neolithic period and followed by the Bronze Age. It was a period of Megalithic culture, the appearance of the first significant economic stratification, and probably the earliest presence of Indo-European speakers. The economy of the Chalcolithic, even in the regions where copper was not yet used, was no longer that of peasant communities and tribes: some materials began to be produced in specific locations and distributed to wide regions. Mining of metal and stone was particularly developed in some areas, along with the processing of those materials into valuable goods. Ancient Chalcolithic From c. 5000 BC to 3000 BC, copper started being used in the Balkans, Eastern Europe, and Central Europe. From c. 3500 onwards, there was an influx of people into Eastern Europe from the area east of the Volga (Yamnaya culture), creating a plural complex known as Sredny Stog culture. This culture replaced the Dnieper-Donets culture, and migrated northwest to the Baltic and Denmark, where they mixed with natives (TRBK A and C). This may be correlated with the spread of Indo-European languages, known as the Kurgan hypothesis. Near the end of the period, another branch left many traces in the lower Danube area (culture of Cernavodă culture I), in what seems to have been another invasion. Meanwhile, the Danubian Lengyel culture absorbed its northern neighbours of the Czech Republic and Poland over a number of centuries, only to recede in the second half of the period. In Bulgaria and Wallachia (Southern Romania), the Boian-Marica culture evolved into a monarchy with a clearly royal cemetery near the coast of the Black Sea. This model seems to have been copied later in the Tiszan region with the culture of Bodrogkeresztur. Labour specialization, economic stratification and possibly the risk of invasion may have been the reasons behind this development. The influx of early Troy (Troy I) is clear in both the expansion of metallurgy and social organization. In the western Danubian region (the Rhine and Seine basins) the culture of Michelsberg displaced its predecessor, Rössen. Meanwhile, in the Mediterranean basin, several cultures (most notably Chassey in SE France and La Lagozza in northern Italy) converged into a functional union, of which the most significant characteristic was the distribution network of honey-coloured flint. Despite this unity, the