The origin of non-canonical case marking of subjects in Proto-Indo-European

For a long time one of the most bewildering conundrums of Indo- European linguistics has been the issue of how to reconstruct the alignment system of this ancient language state, given the lack of distinction between s and o marking in the Proto-Indo-European neuter nouns and the problem of the Hittite ergative. An additional complication stems from the existence of argument structure constructions where the subject(-like) argument is marked in a different case than the nominative, like the accusative or the dative. Our aim with the present article is to fill two needs with one deed and offer a unified account of this century-long bone of contention. In contribution to the ongoing discussion in the field, we claim that a semantic alignment system, in the terms of Donohue & Wichmann (2008), might not only fit better with the morphological data that are currently reconstructed for the ancestral language, but also with the existence of non-canonically case-marked subjects in general (Barðdal, Bjarnadóttir, et al. 2013; Danesi, Johnson & Barðdal 2017).