Their language is called Tocharian.
Archaeology
The Tarim mummies suggest that precursors of these easternmost speakers of an Indo-European language may have lived in the region of the Tarim Basin from around 1800 BC until finally they were assimilated by Uyghur Turks in the 9th century AD.
“Tocharian donors”, possibly the “Knights with Long Swords” of Chinese accounts, depicted with light hair and light eye color and dressed in Sassanian style. 6th century AD fresco, Qizil, Tarim Basin. Graphical analysis reveals that the third donor from left is performing a Buddhist vitarka mudra. These frescoes are associated with annotations in Tocharian and Sanskrit made by their painters.There is evidence both from the mummies and Chinese writings that many of them had blonde or red hair and blue eyes, characteristics also found in present-day Afghanistan, Pakistan, Tajikistan and Central Asia, due to the populations’ high genetic diversity. This suggests the possibility that they were part of an early migration of speakers of Indo-European languages that ended in what is now the Tarim Basin in western China. According to a controversial theory, early invasions by Turkic speakers may have pushed Tocharian speakers out of the Tarim Basin and into modern Uzbekistan, Tajikistan, Turkmenistan, Pakistan and northern India in the form of Kushans and the Tocharo-Iranic Hephthalites.
The Tarim Basin mummies (1800 BC) and the Tocharian texts and frescoes from the Tarim Basin (AD 800) have been found in the same general geographical area, and are both connected to an Indo-European origin. The faces on these frescos were usually vandalized in the past due to their European features. The mummies and the frescoes both point to White types with light eyes and hair color. There is no evidence that directly connects them however, as no texts were recovered from the grave sites.
A recent article (Hemphill and Mallory, 2004) reaches the following conclusions:
This study confirms the assertion of Han [1998] that the occupants of Alwighul and Krorän are not derived from proto-European steppe populations, but share closest affinities with Eastern Mediterranean populations. Further, the results demonstrate that such Eastern Mediterraneans may also be found at the urban centers of the Oxus civilization located in the north Bactrian oasis to the west. Affinities are especially close between Krorän, the latest of the Xinjiang samples, and Sapalli, the earliest of the Bactrian samples, while Alwighul and later samples from Bactria exhibit more distant phenetic affinities. This pattern may reflect a possible major shift in interregional contacts in Central Asia in the early centuries of the second millennium BC.
However, another theory states that the earliest Bronze Age settlers of the Tarim and Turpan basins originated from the steppelands and highlands immediately north of East Central Asia. These colonists were related to the Afanasievo culture which exploited both open steppelands and upland environments employing a mixed agricultural economy. The Afanasievo culture formed the eastern linguistic periphery of the Indo-European continuum of languages whose centre of expansion lay much farther to the west, north of the Black and Caspian seas. This periphery was ancestral to the historical Tocharian languages. See J. P. Mallory and Victor H. Mair, The Tarim Mummies — 2000 Thames and Hudson Ltd ISBN 0-500-05101-1.
LANGUAGE:
The Tocharians appear to have originally spoken two distinct languages of the Indo-European Tocharian family, an Eastern (”A”) form and a Western (”B”) form. According to some, only the Eastern (”A”) form can be properly called “Tocharian”, as the native name for the Western form is referred to as Kuchean (see below). Commonalities between the Tocharian languages and various other Indo-European language families (as with Germanic, Balto-Slavic, even Italic or Greek) have been suggested, but the evidence does not support any close relationship with any other family. The only consensus is that Tocharian was already far enough removed, at an early date, from the other eastern I-E proto-languages (Proto-Balto-Slavic and Proto-Indo-Iranian), not to share some of the common changes that PBS and PII share, such as early palatalization of velars.
Tocharian A of the eastern regions seems to have declined in use as a popular language or mother tongue faster than did Tocharian B of the west. Tocharian A speakers probably yielded their original language to Turkic languages of immigrating Turkic peoples, while Tocharian B speakers were more insulated from outside linguistic influences. It appears that Tocharian A ultimately became a liturgical language, no longer a living one, at the same time that Tocharian B was still widely spoken in daily life. Among the monasteries of the lands inhabited by Tocharian B speakers, Tocharian A seems to have been used in ritual alongside the Tocharian B of daily life.
Besides the religious Tocharian texts, the texts include monastery correspondence and accounts, commercial documents, caravan permits, medical and magical texts, and a love poem. Their manuscript fragments, of the 8th centuries, suggest that they were no longer either as nomadic or “barbarian (hu)” as the Chinese had considered them.
Tocharians in Indian Literature
Sanskrit literature in numerous instances refers to the Tocharians as Tusharas, Tukharas, Tokharas and Tuharas etc.
The Atharavaveda-Parishishta associates the Tusharas with the Sakas, Yavanas and the Bahlikas. It also juxtaposes the Kambojas with the Bahlikas. This shows the Tusharas probably were neighbors to the Shakas, Bahlikas, Yavanas and the Kambojas in Transoxian region.
The Rishikas are said to be same people as the Yuezhi
Thanks for the post about the Tocharians. It is interesting how some languages get propagated (even as they change over centuries) while other languages fall into disuse and become extinct.
The other Indo-European languages in the East are all satem languages, including the Indian & Iranian languages, and also the Slavic language family.
Tocharian B for "8" is okt (cf. Latin octo, Czech osm) and for "100" is kante.