distinguished from the preceding Mesolithic cultures and far more visible as a result of the introduction of pottery. Southwest Siberia reached a neolithic cultural level during the Chalcolithic, which began here towards the end of the fourth millennium BC, which roughly coincided with the introduction of copper–working. In the northern and eastern regions, there is no detectable change. Bronze Age (c. 2400–800 BC) In the second half of the third millennium BC, bronzeworking reached the cultures of western Siberia. Chalcolithic groups in the eastern Ural foothills developed the so-called Andronovo culture, which took various local forms. The settlements of Arkaim, Olgino and Sintashta are particularly notable as the earliest evidence for urbanisation in Siberia. In the valleys of the Ob and Irtysh the same ceramic cultures attested there during the neolithic continue; the changes in the Baikal region and Yakutia were very slight. In the middle Bronze Age (c. 1800–1500 BC), the west Siberian Andronovo culture expanded markedly to the east and even reached the Yenissei valley. In all the local forms of the Andronovo culture, homogenous ceramics are found, which also extended to the cultures on the Ob. Here, however, unique neolithic ceramic traditions were maintained as well. With the beginning of the late Bronze Age (c. 1500–800 BC), crucial cultural developments took place in southern Siberia. The Andronovo culture dissolved; its southern successors produced an entirely new form of pottery, with bulbous ornamental elements. At the same time the southern cultures also developed new forms of bronze working, probably as a result of influence from the southeast. These changes were especially significant in the Baikal region. There, the chalcolithic material culture which had continued up to this time was replaced by a bronze-working pastoralist culture. There and in Yakutia, bronze was only used as a material for the first time at this point. The Ymyakhtakh culture (c. 2200–1300 BC) was a Late Neolithic culture of Siberia, with a very large archaeological horizon. Its origins seem to be in the Lena river basin of Yakutia, and also along the Yenisei river. From there it spread both to the east and to the west. Iron Age (c. 800 BC - AD 500) The cultural continuity on the Ob continued in the first millennium BC, as the Iron Age began in Siberia; the local ceramic style continues there even in this period. A much larger break occurred in the central Asian