From the 3rd century B.C., Central Asia experienced nomadic expansions of Altaic-speaking oriental-looking people, and their incursions continued for hundreds of years, beginning with the Hsiung-Nu (who may be ancestors of the Huns), in ~300 B.C., and followed by the Turks, in the 1st millennium A.D., and the Mongol expansions of the 13th century. High levels of haplogroup 10 and its derivative, haplogroup 36 [C-M210, are found in most of the Altaic-speaking populations and are a good indicator of the genetic impact of these nomadic groups. The expanding waves of Altaic-speaking nomads involved not only eastern Central Asia—where their genetic contribution is strong, [...]—but also regions farther west, like Iran, Iraq, Anatolia, and the Caucasus, as well as Europe, which was reached by both the Huns and the Mongols. In these western regions, however, the genetic contribution is low or undetectable (...), even though the power of these invaders was sometimes strong enough to impose a language replacement, as in Turkey and Azerbaijan (...). The difference could be due to the population density of the different geographical areas. Eastern regions of Central Asia must have had a low population density at the time, so an external contribution could have had a great genetic impact. In contrast, the western regions were more densely inhabited, and it is likely that the existing populations were more numerous than the conquering nomads, therefore leading to only a small genetic impact. Thus, the admixture estimate from North-East Asia is high in the east, but is barely detectable west of Uzbekistan..Another study shows that the Uzbeks are closely related to other Turkic peoples of Central Asia and rather distant from Iranian people. The study also analysed the maternal and paternal DNA haplogroups and shows that Turkic speaking groups are more homogenous than Iranian speaking groups.