This article contributes to the case for reconstructing verb agreement for Proto-Tibeto-Burman. It shows first that, given the distribution of cognate agreement systems across the family, there is no alternative to reconstructing it for the proto-language. Secondly it describes the paths by which agreement has been lost in those languages where it is absent.

Evidence is presented to demonstrate the prevalence of evidence for the PTB paradigm in languages across the family. It is shown that, contrary to assertions which have been made in the literature, the agreement systems of Jinghpaw, Nocte, and Northern Chin are cognate to those of the socalled “Rung” branches (Kiranti, rGyalrongic-Qiangic, Nungish, and West Himalayan), and that even without, but especially with, this evidence the “Rung” hypothesis is inconsistent with other proposals for subgrouping Tibeto-Burman. Once the cognacy of the Jinghpaw and Nocte systems is recognized, there is no further reason to believe in a genetic “Rung” unit. Several case studies are presented which show that agreement systems can be quickly and easily lost in TB languages, as a result of intense language contact and/or through the replacement of older finite structures by innovative new constructions based on clausal nominalization.

The South Central languages show two distinct indexation paradigms: a set of postverbal agreement words, incorporating person-number indexation and tense/aspect/polarity marking, inherited from a pre-SC ancestor, and a set of proclitic pronouns, otherwise used as possessive clitics on nouns. The interaction of the two series differs across the branch. Some Northern Peripheral have full competing paradigms, with the choice of one or the other marking register. At the other extreme, languages in the Central group use only the innovative proclitic paradigm, though it may incorporate pieces from the archaic postverbal paradigm. In most Northwestern and some Southern Peripheral languages the paradigms are associated with transitivity and/or polarity, with the proclitic paradigm found in affirmative transitive and the postverbal in negative intransitive clauses. We find great variation across the branch in the interaction of indexation with transitivity. Many languages have innovated object-indexation, a few have developed inverse markers and/or hierarchical indexation patterns.

Research on comparative Tibeto-Burman verbal morphology has achieved preliminary reconstructions of the hierchical patterns and position classes of the agreement system. The status of the prefixes which are part of the system in some branches remains problematic. Only one true personal agreement prefix, 2nd person #te-, appears to be as ancient as the suffixal agreement series. Others are language-specific innovations more recent than PTB. One clue to the origin of these secondary prefixes, as David Watters and Sun Hongkai have suggested, is their resemblance to possessive pronominal prefixes. The 2nd person k- prefix which several scholars reconstruct is a secondary intrusion of a 2nd person possessive prefix into the verb paradigm. The “marked scenario” prefix found in some Nung and Kiranti languages is likewise a secondary innovation in which original #te- was replaced by 2nd person #na- or #i-, the latter originally a 1pl Inclusive index.