text: A glottochronological reconstruction based on analysis of isoglosses and Sinicisms points to the timing of the r/z split at around 56 BCE–48 CE. As Anna Dybo puts it, that may be associated with
  the historical situation that can be seen in the history of the Huns' division onto the Northern and Southern [groups]: the first separation and withdrawal of the Northern Huns to the west has occurred, as was stated above, in 56 BC,... the second split of the (Eastern) Huns into the northern and southern groups happened in 48 AD.
  Dybo suggests that during that period, the Northern branch steadily migrated from Western Mongolia through Southern Xinjiang into the north's Dzungaria and then finally into Kazakhstan's Zhetysu until the 5th century.
  There was no fortis-lenis contrast in word-initial position: the initial stops were always *b, *t, *k, the affricate was always *č (*ç) and the sibilant was always *s. In addition, the nasals and the liquids did not occur in that position either.
  Like in many modern Turkic languages, the velars /k/, /g/, and possibly /ŋ/ seem to have had back and front allophones ( and ,  and ,  and ) according to their environments, with the velar allophones occurring in words with front vowels, and uvular allophones occurring in words with back vowels. The lenis stops /b/, /d/ and /g/~/ɢ/ may have tended towards fricatives intervocalically.