Verb agreement, head-marking vs. dependent-marking, and the "deconstruction" of Tibeto-Burman morpho-syntax

Since the mid-1970's, the question of whether or not a verb agreement system1 (VAS) should be reconstructed for Proto-Tibeto-Bunnan (PTB) has been a controversial topic, but because of the large amount of work published arguing in favor of reconstructing a VAS for PTB, especially by James J. Bauman (1974, 1975a, 1975b, 1979) and Scott DeLancey (1980, 1983, 1988, 1989, to appear), many people have begun to accept the existence of a VAS in PTB as received knowledge. In a recent paper on verb agreement systems in Tibeto-Burman, Scott DeLancey states that 'There can no longer be any serious doubt that a system of verb agreement must be attributed to Proto-Tibeto-Bunnan (PTB)' (DeLancey 1988: 1). Though the number of papers supporting this position is quite large, I would like to raise several serious doubts about the theoretical and methodological basis for reconstructing a VAS for PTB' and at the same time argue for the use of functionally and typologically based theories of grammar, as exemplified by the head-marking/dependent-marking distinction developed in Nichols 1986, in diachronic syntax and syntactic reconstruction