Sidwell (2015c) tentatively suggests that Austroasiatic may have begun to split up 5,000 years B.P. during the Neolithic transition era of mainland Southeast Asia, with all the major branches of Austroasiatic formed by 4,000 B.P. Austroasiatic would have had two possible dispersal routes from the western periphery of the Pearl River watershed of Lingnan, which would have been either a coastal route down the coast of Vietnam, or downstream through the Mekong River via Yunnan.
sˈɪdwɛl tˈuː θˈaʊzənd fˈɪftiːn sˈiː tˈɛntətˌɪvli sədʒˈɛsts ðæt ˌɔːstɹoʊsɪˈæɾɪk mˌeɪhɐv bɪɡˈʌn tə splˈɪt ˌʌp fˈaɪv,zˈiəɹoʊzˈiəɹoʊ zˈiəɹoʊ jˈɪɹz bˈiː.pˈiː. dˈʊɹɹɪŋ ðə nˌiːoʊlˈɪθɪk tɹænsˈɪʃən ˈiəɹə ʌv mˈeɪnlənd sˈaʊθiːst ˈeɪʒə, wɪð ˈɔːl ðə mˈeɪdʒɚ bɹˈæntʃᵻz ʌv ˌɔːstɹoʊsɪˈæɾɪk fˈɔːɹmd baɪ fˈoːɹ,zˈiəɹoʊzˈiəɹoʊ zˈiəɹoʊ bˈiː.pˈiː. ˌɔːstɹoʊsɪˈæɾɪk wʊdhɐv hæd tˈuː pˈɑːsᵻbəl dɪspˈɜːsəl ɹˈaʊts fɹʌmðə wˈɛstɚn pɚɹˈɪfɚɹi ʌvðə pˈɜːl ɹˈɪvɚ wˈɔːɾɚʃˌɛd ʌv lˈɪŋnən, wˌɪtʃ wʊdhɐv bˌɪn ˈiːðɚɹ ɐ kˈoʊstəl ɹˈaʊt dˌaʊn ðə kˈoʊst ʌv vˌiːətnˈɑːm, ɔːɹ dˈaʊnstɹiːm θɹuː ðə mˈɛkɑːŋ ɹˈɪvɚ vˈaɪə jˈʌnən.