This period extends from 2500 BC to 1800 or 1700 BC, depending on the region. The dates are general for the whole of Europe, and the Aegean area was already fully in the Bronze Age. c. 2500 BC the new Catacomb culture (proto-Cimmerians?), whose origins were obscure but were also Indo-Europeans, displaced the Yamna peoples in the regions north and east of the Black Sea, confining them to their original area east of the Volga. The Catacomb culture was the first to introduce corded pottery decorations into the steppes and shows a profuse use of the polished battle axe, providing a link to the West. Parallels with the Afanasevo culture, including provoked cranial deformations, provided a link to the East. Some of them infiltrated Poland and may have played a significant but unclear role in the transformation of the culture of the Globular Amphorae into the new Corded Ware culture.