Johnson 2004 - CDLI - UCLA

diachronic origins (as opposed to the typological variation) of ergativity, since it was
precisely the question of origins that had given rise—a century before—to the obligatory-
passive hypothesis as well as it corollary to the effect that all languages “start out” as
nominative/accusative languages and change into ergative languages under certain
circumstances.
Several years later, Trask (1979) would attempt to split the difference in historical
terms, arguing that the typological framework proposed by Silverstein can actually come
into being in historical terms in at least two different ways: Type A ergativity develops
from an obligatory passivization, whereas Type B ergativity results from the
grammaticalization of a possessive construction. Trask describes Type B ergativity,
which bears a certain resemblance to the situation in Sumerian, as follows:
Now in a language lacking a verb ‘have’, possessive predications are commonly
made by putting the possessor into an oblique case, most often the dative,
locative, or genitive—carrying an overt mark. And re-interpretation of such a
possessor as an agent would automatically bring about ergative case-marking.
Thus a sentence of the general form To me / Of me / At me (is) a window broken,
on being re-interpreted to mean ‘I have broken a window’, would yield a typical
Type B pattern, with the agent overtly marked, the patient unmarked, the verb
agreeing with the patient in number and gender but not in person, the verb not
agreeing with the agent at all, and the whole thing confined to the perfect (Trask
1979, 398).
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