Proto-Sino-Tibetan (PST) is the linguistic reconstruction of the Sino-Tibetan proto-language and the common ancestor of all languages in it, including the Sinitic languages, the Tibetic languages, Yi, Bai, Burmese, Karen, Tangut, and Naga. Paul K. Benedict (1972) placed a particular emphasis on Old Chinese, Classical Tibetan, Jingpho, Written Burmese, Garo, and Mizo in his discussion of Proto-Sino-Tibetan.[1]
While Proto-Sino-Tibetan is commonly considered to have two direct descendants, Proto-Sinitic and Proto-Tibeto-Burman,[2] in recent years several scholars have argued that this was not well-substantiated,[3] and have taken to calling the group "Trans-Himalayan".[4] In this case, Proto-Tibeto-Burman may be considered as equivalent to Proto-Sino-Tibetan if Sinitic is indeed not the first branch to split from Proto-Sino-Tibetan.[5]
Reconstructed features include prefixes such as the causative s-, the intransitive m-, the miscellaneous b-, d-, g-, and r-, suffixes -s, -t, and -n, and a set of conditioning factors that resulted in the development of tone in most languages of the family.[6] The existence of such elaborate system of inflectional changes in Proto-Sino-Tibetan makes the language distinctive from some of its modern descendants, such as the Sinitic languages, which have mostly or completely become analytic.
Proto-Sino-Tibetan, like Old Chinese, also included numerous consonant clusters, and was not a tonal language.
The table below shows consonant phonemes reconstructed by Benedict.[1][page needed]
The reconstruction by Peiros & Starostin suggests a much more complex consonant inventory.[7] The phonemes in brackets are reconstructions that are considered dubious.
The following tables show the reconstruction of Proto-Sino-Tibetan phonemes by Nathan Hill (2019).[8]
The consonants /p t k q ʔ m n ŋ l r j/ can take coda position, as well as the cluster /rl/. While Hill does not reconstruct /j/ as an initial consonant due to Baxter and Sagart's Old Chinese reconstruction lacking such a phoneme, he mentions that Jacques and Schuessler suggest a /j/ initial for some Old Chinese words due to potential Tibetan or Rgyalrongic cognates.[10]
Hill also claims that his reconstruction is incomplete, as it does not account for Tibetic palatalization, proto-Burmish preglottalization, Sinitic aspirates, and the Sinitic type A and B distinction of syllables.
The sound correspondences cited by Hill (2019) are as follows. Hill bases his correspondences to Old Chinese off of the Baxter-Sagart reconstruction, and thus that reconstruction will be used in the following correspondence tables.
Note that many cognate sets with /p t k b d g/ initials between Old Chinese, Tibetan and Burmese agree in every phoneme in a given word except for whether an initial consonant is voiced or not. Jacques explains these discrepancies as at least partially triggered by pre-syllables that were lost or decayed on the way to Chinese, Tibetan and Burmese.[11]
In Gong Huangcheng's reconstruction of the Proto-Sino-Tibetan language, the finals *-p, *-t, *-k, *-m, *-n, and *-ŋ in Proto-Sino-Tibetan remained in Proto-Sinitic and Proto-Tibeto-Burman. However, in Old Chinese, the finals *-k and *-ŋ that came after the close vowel *-i- underwent an irregular change of *-k＞*-t and *-ŋ ＞*-n. In Proto-Tibeto-Burman, *-kw and *-ŋw underwent a sound change to become *-k and *-ŋ respectively, while in Old Chinese those finals remained until Middle Chinese, where the finals underwent the same sound change.[12]
Furthermore, in Proto-Tibeto-Burman, the finals *-g, *-gw, and *-d underwent the following changes:
Words which do not have reliable Sinitic parallels are accompanied by a (TB).