The present state of knowledge about Kurdish allows, at least roughly, drawing the approximate borders of the areas where the main ethnic core of the speakers of the contemporary Kurdish dialects was formed. The most argued hypothesis on the localisation of the ethnic territory of the Kurds remains D.N. Mackenzie's theory, proposed in the early 1960s. Developing the ideas of P. Tedesco and regarding the common phonetic isoglosses shared by Kurdish, Persian, and Baluchi, D.N. Mackenzie concluded that the speakers of these three languages form a unity within Northwestern Iranian. He has tried to reconstruct such a Persian-Kurdish-Baluchi linguistic unity presumably in the central parts of Iran. According to his theory, the Persians (or Proto-Persians) occupied the province of Fars in the southwest (proceeding from the fact that the Achaemenids spoke Persian), the Balochs (Proto-Balochs) inhabited the central areas of Western Iran, and the Kurds (Proto-Kurds), in the wording of G. Windfuhr (1975: 459), lived either in northwestern Luristan or in the province of Isfahan. In the second half of the 10th century there were five Kurdish principalities: in the north the Shaddadid (951–1174) (in parts of Armenia and Arran) and Rawadid (955–1221) in Tabriz and Maragheh, in the East the Hasanwayhids (959–1015), the Annazid (990–1117) (in Kermanshah, "Dinawar" and Khanaqin) and in the West the Marwanid (990–1096) of Diyarbakır. Later in the 12th century, the Kurdish Hazaraspid dynasty established its rule in southern Zagros and Luristan and conquered territories of Kuhgiluya, Khuzestan and Golpayegan in the 13th century and annexed Shushtar, Hoveizeh and Basra in the 14th century. One of these dynasties may have been able, during the decades, to impose its supremacy on the others and build a state incorporating the whole Kurdish country if the course of history had not been disrupted by the massive invasions of tribes surging out of the steppes of Central Asia. Having conquered Iran and imposed their yoke on the caliph of Baghdad, the Seljuq Turks annexed the Kurdish principalities one by one.