estimated at 2.12 million years old. End of the Stone Age Innovation of the technique of smelting ore is regarded as ending the Stone Age and beginning the Bronze Age. The first highly significant metal manufactured was bronze, an alloy of copper and tin or arsenic, each of which was smelted separately. The transition from the Stone Age to the Bronze Age was a period during which modern people could smelt copper, but did not yet manufacture bronze, a time known as the Copper Age (or more technically the Chalcolithic or Eneolithic, both meaning 'copper–stone'). The Chalcolithic by convention is the initial period of the Bronze Age. The Bronze Age was followed by the Iron Age. The transition out of the Stone Age occurred between 6000 and 2500 BC for much of humanity living in North Africa and Eurasia. The first evidence of human metallurgy dates to between the 6th and 5th millennia BC in the archaeological sites of the Vinča culture, including Majdanpek, Jarmovac, Pločnik, Rudna Glava in modern-day Serbia. Ötzi the Iceman, a mummy from about 3300 BC, carried with him a copper axe and a flint knife. In some regions, such as Sub-Saharan Africa, the Stone Age was followed directly by the Iron Age. The Middle East and Southeast Asian regions progressed past Stone Age technology around 6000 BC. Europe, and the rest of Asia became post-Stone Age societies by about 4000 BC. The proto-Inca cultures of South America continued at a Stone Age level until around 2000 BC, when gold, copper, and silver made their entrance. The peoples of the Americas notably did not develop a widespread behavior of smelting bronze or iron after the Stone Age period, although the technology existed. Stone-tool manufacture continued even after the Stone Age ended in a given area. In Europe and North America, millstones were in use until well into the 20th century, and still are in many parts of the world. Concept of the Stone Age The terms "Stone Age", "Bronze Age", and "Iron Age" are not intended to suggest that advancements and time periods in prehistory are only measured by the type of tool material, rather than, for example, social organization, food sources exploited, adaptation to climate, adoption of agriculture, cooking, settlement, and religion. Like pottery, the typology of the stone tools combined with the relative sequence of the types in various regions provide a chronological framework