Guillaume Jacques has a new paper out on the subject of the Proto-Sino-Tibetan person-marking debate, a subject which I’ve been meaning to run a series on for some time. To summarize, the question of the PST person-marking debate is whether such a thing existed. Sino-Tibetan historical linguistics is not as complete as Indo-European historical linguistics, which over the course of about a hundred and fifty years progressed toward its current metastable state, where everybody is pretty sure that the current consensus reconstruction of Proto-Indo-European must be wrong on a fundamental level but nobody has any idea how to fix it. In fact, the internal cladistic structure of Sino-Tibetan is still controversial.
As it would be. The most potentially conservative morphology is found in the Rgyalrongic (also known as rGyalrong, Gyalrong, Gyarong, Jiarong, etc., a state of affairs that’s still better than that of its constituents: could you guess that Lavrung and Khroskyabs are the same language?) and Kiranti branches, which LaPolla, the main proponent of the view that PST had no verbal person-marking, says are related at a more recent level (the ‘Rung group’), and which Jacques, the main proponent of the view that it did, says are not. If PST had verbal person-marking, Rungic probably isn’t real; if Rungic is real, PST probably didn’t have verbal person-marking; if PST didn’t have verbal person-marking, Rungic probably is real; and if Rungic is real, PST probably didn’t have verbal person-marking.
Most of the evidence bearing on the debate comes from Rgyalrongic and Kiranti, but some comes from Tangut, Old Tibetan, and Old Chinese.
In Tangut, the person-marking suffixes are identical to the pronouns: the first-person singular pronoun and the first-person singular marker are both nga2, the second-person singular pronoun and the second-person singular marker are both nja2, and the second-person plural pronoun and the first- or second-person plural marker are both nji2. Nga2 and nga2 are even written with the same character, although the other person markers have characters distinct from the pronouns.
However, the second-person plural pronoun nji2 can be used as an honorific singular, as in Old Tibetan and Early Modern English—in which case the verb takes the second-person singular marker nja2. If, that is, the verb is intransitive or has a third-person object: Tangut, you see, does not have accusative verbal person-marking.
If a Tangut verb is intransitive, it agrees with the agent of the verb. If it’s transitive and has a second-person patient (in which case it can’t have a second-person agent), it takes -nja2; if the patient is first-person, it takes -nga2, and if the patient is third-person, it takes –nga2 if the agent is first-person singular, -nja2 if the patient is second-person singular, and -nji2 if the patient is first- or second-person plural. (Third-person arguments are never marked.)
Even more confusingly (and more interestingly for our purposes), there’s a closed class of verbs in Tangut that have two stems, which of course are called Stem A and Stem B. Stem B is only used for first- or second-person singular reflexive verbs or verbs with a first- or second-person singular agent and a third-person patient. For example:
sjij1 mjo2 gja1 .jij1 rjyr2.wjij1 ljij2 mjy1djij2 lhjwo1djij2 mjy1tchjy1lji2nga2
“Today I see the army leave, but I will not see it return.”
.jwar1 gja1 ghu1 .jij1 ljiij2 lja1 zji.j1 kjij1ljij2nga2
“When the Yue army comes to destroy Wu, it will see me.”
This doesn’t look like a difference—in fact, in the conventional transcription of Tangut (which I’ve ASCIIfied slightly), with its bizarre and unnecessary proliferation of js, it looks like a typo—but the conventional transcription of Tangut is thankfully always accompanied by character numbers, which in this case are 4803 for the stem A lji2 and 0046 for the stem B ljij2; and Marc Miyake once reconstructed them as the more sensible 2lɨi and 2le. (He writes the tone before the syllable.)
This state of affairs must be conservative to some degree, but nobody knows where it came from.