The development of subject case marking in Omotic Mao

The Mao subgroup of the Omotic family shows various degrees of development of morphological subject case marking which results from largely internal, but very similar historical pathways across the group. These different patterns find their source in an older prenominal demonstrative + NP + bound postnominal form construction; in this construction the bound postnominal form of this construction is itself related to (and often reduced from) the corresponding prenominal demonstrative.  Evidence of such a construction is found in each of the four Mao languages but in only three of the languages has the construction become clearly associated with marking grammatical subjects. The pathway toward subject case marking appears to have begun with the demonstrative construction becoming associated with topical referents in discourse. In three of the four Mao languages, the prenominal demonstrative then became associated with definiteness (a typologically common development from topic-marking devices); in those same three languages the frequent co-association between topics and grammatical subjects led to the postnominal form developing subject case marking status. The prenominal definite marker (the erstwhile demonstrative) eventually became emancipated from the postnominal case marker to various degrees across the Mao group. The degree to which subject-development and emancipation between the prenominal and postnominal portions of this demonstrative construction has become established in each of the languages has led to the diverse patterns across the subgroup.