Eastern Iranian is thought to have separated from Western Iranian in the course of the later 2nd millennium BC, and was possibly located at the Yaz culture. With Greek presence in Central Asia, some of the easternmost of these languages were recorded in their Middle Iranian stage, while almost no records of the Scytho-Sarmatian continuum stretching from Kazakhstan west across the Pontic steppe to Ukraine have survived. Some authors find that the Eastern Iranian people had an influence on Russian folk culture. Middle Persian/Dari spread around the Oxus River region, Afghanistan, and Khorasan after the Arab conquests and during Islamic-Arab rule. The replacement of the Pahlavi script with the Arabic script in order to write the Persian language was done by the Tahirids in 9th century Khorasan. The Persian Dari language spread and led to the extinction of Eastern Iranic languages like Bactrian and Khorezmian, with only a tiny amount of Sogdian descended Yaghnobi speakers remaining among the now Persian speaking Tajik population of Central Asia, due to the fact that the Arab-Islamic army which invaded Central Asia also included some Persians who later governed the region like the Samanids. Persian was rooted into Central Asia by the Samanids.
Classification
Eastern Iranian remains a single dialect continuum subject to common innovation. Traditional branches, such as "Northeastern", as well as Eastern Iranian itself, are better considered language areas rather than genetic groups. The languages are as follows: ;Old Iranian
In Yaghnobi initial *č- was lost, there should be expected from *čatfṓr if Yaghnobi didn't loss the initial syllable due to a stress shift
Lenition of voiced stops
Common to most Eastern Iranian languages is a particularly widespread lenition of the voiced stops *b, *d, *g. Between vowels, these have been lenited also in most Western Iranian languages, but in Eastern Iranian, spirantization also generally occurs in the word-initial position. This phenomenon is however not apparent in Avestan, and remains absent from Ormuri-Parachi. A series of spirant consonants can be assumed to have been the first stage: *b > *β, *d > *ð, *g > *ɣ. The voiced velar fricative has mostly been preserved. The labial member has been well-preserved too, but in most languages has shifted from a voiced bilabial fricative to the voiced labiodental fricative. The dental member has proved the most unstable: while a voiced dental fricative is preserved in some Pamir languages, it has in e.g. Pashto and Munji lenited further to. On the other hand, in Yaghnobi and Ossetian, the development appears to have been reversed, leading to the reappearance of a voiced stop.
English
Avestan
Pashto
Munji
Sanglechi
Wakhi
Shughni
Parachi
Ormuri
Yaghnobi
Ossetic
ten
dasa
las
los / dā
dos
δas
δis
dōs
das
das
dæs
cow
gav-
ɣwā
ɣṓw
uɣūi
ɣīw
žōw
gū
gioe
ɣōw
qug
brother
brātar-
wrōr
vəróy
vrūδ
vīrīt
virṓd
byā
virṓt
ærvad
The consonant clusters *ft and *xt have also been widely lenited, though again excluding Ormuri-Parachi, and possibly Yaghnobi.
External influences
The neighboring Indo-Aryan languages have exerted a pervasive external influence on the closest neighbouring Eastern Iranian, as it is evident in the development in the retroflex consonants and aspirates. A more localized sound change is the backing of the former retroflex fricative ṣ̌, to x̌ or to x, found in the Shughni–Yazgulyam branch and certain dialects of Pashto. E.g. "meat": ɡuṣ̌t in Wakhi and γwaṣ̌a in Southern Pashto, but changes to guxt in Shughni, γwax̌a in Central Pashto and γwaxa in Northern Pashto.