The earliest postulated expansion out of the steppe is that of the Indo-Europeans, who spread their languages into the Middle East, South Asia, and the borders of China, where the Tocharians resided.
ðɪ ˈɜːlɪɪst pˈɔstʃʊlˌeɪɾᵻd ɛkspˈænʃən ˌaʊɾəv ðə stˈɛp ɪz ðæt ʌvðɪ ˈɪndoʊjˌʊɹɹəpˈiənz, hˌuː spɹˈɛd ðɛɹ lˈæŋɡwɪdʒᵻz ˌɪntʊ ðə mˈɪdəl ˈiːst, sˈaʊθ ˈeɪʒə, ænd ðə bˈoːɹdɚz ʌv tʃˈaɪnə, wˌɛɹ ðə tətʃˈɛɹiənz ɹᵻsˈaɪdᵻd.