The origins of the Turkmen may be traced back to the Oghuz confederation of nomadic pastoral tribes of the early Middle Ages, who lived in present-day Mongolia and around Lake Baikal in present-day southern Siberia. This confederation was composed of Turkic-speaking peoples who formed the basis of powerful steppe empires in Inner Asia. In the second half of the 8th century, Oghuz components migrated through Jungaria into Central Asia, and Arabic sources located them under the term Guzz in the area of the middle and lower Syrdariya in the 8th century. By the 10th century, the Oghuz had expanded west and north of the Aral Sea and into the steppe of present-day Kazakhstan, absorbing not only Iranians but also Turks from the Kipchak and Karluk ethnolinguistic groups. In the 11th century, the renowned Muslim Turk scholar Mahmud al-Kashgari described the language of the Oghuz and Turkmen as distinct from that of other Turks and identified twenty-two Oghuz clans or sub-tribes, some of which appear in later Turkmen genealogies and legends as the core of the early Turkmen.