The Eastern Iranian languages are a subgroup of the Iranian languages emerging in Middle Iranian times (from c. the 4th century BC). The Avestan language is often classified as early Eastern Iranian. As opposed to the Middle Western Iranian dialects, the Middle Eastern Iranian preserves word-final syllables. The largest living Eastern Iranian language is Pashto, with some 40-60 million speakers between the Oxus River in Afghanistan and the Indus River in Pakistan. The second-largest language is Ossetic with roughly 600,000 speakers. All other languages have fewer than 200,000 speakers combined. Most living Eastern Iranian languages are spoken in a contiguous area, in southern and eastern Afghanistan as well as the adjacent parts of western Pakistan, Gorno-Badakhshan Autonomous Province of eastern Tajikistan, and the far west of Xinjiang region of China. There are also two living members in widely separated areas: the Yaghnobi language of northwestern Tajikistan (descended from Sogdian), and the Ossetic language of the Caucasus (descended from Scytho-Sarmatian). These are remnants of a vast ethno-linguistic continuum that stretched over most of Central Asia, Eastern Europe, and parts of the Caucasus, and West Asia in the 1st millennium BC, otherwise known as Scythia. The large Eastern Iranian continuum in Eastern Europe would continue up to including the 4th century AD, with the successors of the Scythians, namely the Sarmatians. History Western Iranian is thought to have separated from Proto-Iranian in the course of the later 2nd millennium BC not long after Avestan, possibly occurring in the Yaz culture. Eastern Iranian followed suit, and developed in place of Proto-Iranian, spoken within the Andronovo horizon. With Greek presence in Central Asia, some of the easternmost of these languages were recorded in their Middle Iranian stage (hence the "Eastern" classification), 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