Indo-Aryan languages have the longest documented historical record, with the earliest attested texts going back to 1900 bce. Old Indo-Aryan (Vedic, Sanskrit) had an inflectional case-marking system where nominatives functioned as subjects. Objects could be realized via several different case markers (depending on semantic and structural factors), but not the nominative. This inflectional system was lost over the course of several centuries during Middle Indo-Aryan, resulting in just a nominative–oblique inflectional distinction. The New Indo-Aryan languages innovated case markers and developed new case-marking systems. Like in Old Indo-Aryan, case is systematically used to express semantic differences via differential object marking constructions. However, unlike in Old Indo-Aryan, many of the New Indo-Aryan languages are ergative and all allow for non-nominative subjects, most prominently for experiencer subjects. Objects, on the other hand, can now also be unmarked (nominative), usually participating in differential object marking. The case-marking patterns within New Indo-Aryan and across time have given rise to a number of debates and analyses. The most prominent of these include issues of case alignment and language change, the distribution of ergative vs. accusative vs. nominative case, and discussions of markedness and differential case marking.
While in phonology Middle Indo-Aryan (MIA) dialects preserved the phonological system of Old Indo-Aryan (OIA) virtually intact, their morphosyntax underwent far-reaching changes, which altered fundamentally the synthetic morphology of earlier Prākrits in the direction of the analytic typology of New Indo-Aryan (NIA). Speaking holistically, the “accusative alignment” of OIA (Vedic Sanskrit) was restructured as an “ergative alignment” in Western IA languages, and it is precisely during the Late MIA period (ca. 5th–12th centuries ce) when we can observe these matters in statu nascendi. There is copious literature on the origin of the ergative construction: passive-to-ergative reanalysis; the ergative hypothesis, i.e., that the passive construction of OIA was already ergative; and a compromise stance that neither the former nor the latter approach is fully adequate. In the spirit of the complementary view of these matters, more attention has to be paid to various pathways in which typological changes operated over different kinds of nominal, pronominal and verbal constituents during the crucial MIA period. (a) We shall start with the restructuring of the nominal case system in terms of the reduction of the number of cases from seven to four. This phonologically motivated process resulted ultimately in the rise of the binary distinction of the “absolutive” versus “oblique” case at the end of the MIA period). (b) The crucial role of animacy in the restructuring of the pronominal system and the rise of the “double-oblique” system in Ardha-Māgadhī and Western Apabhramśa will be explicated. (c) In the verbal system we witness complete remodeling of the aspectual system as a consequence of the loss of earlier synthetic forms expressing the perfective (Aorist) and “retrospective” (Perfect) aspect. Early Prākrits (Pāli) preserved their sigmatic Aorists (and the sigmatic Future) until late MIA centuries, while on the Iranian side the loss of the “sigmatic” aorist was accelerated in Middle Persian by the “weakening” of s > h > Ø. (d) The development and the establishment of “ergative alignment” at the end of the MIA period will be presented as a consequence of the above typological changes: the rise of the “absolutive” vs. “oblique” case system; the loss of the finite morphology of the perfective and retrospective aspect; and the recreation of the aspectual contrast of perfectivity by means of quasinominal (participial) forms. (e) Concurrently with the development toward the analyticity in grammatical aspect, we witness the evolution of lexical aspect (Aktionsart) ushering in the florescence of “serial” verbs in New Indo-Aryan. On the whole, a contingency view of alignment considers the increase in ergativity as a by-product of the restoration of the OIA aspectual triad: Imperfective–Perfective–Perfect (in morphological terms Present–Aorist–Perfect). The NIA Perfective and Perfect are aligned ergatively, while their finite OIA ancestors (Aorist and Perfect) were aligned accusatively. Detailed linguistic analysis of Middle Indo-Aryan texts offers us a unique opportunity for a deeper comprehension of the formative period of the NIA state of affairs.