From clause conjoining to clause chaining in Dumut languages of New Guinea

The Dumut languages Mandobo, South Wambon and North Wambon are a subgroup of the Awyu-Dumut family. They form a dialect chain that represents stages of the development from clause conjoining with independent verb forms to clause chaining with dependent verb forms that express switch-reference. South Wambon represents the first stage in which there is coordination reduction of tense and subject person-number suffixes in thematic continuity conditions. This process created three verb types: fully finite verbs; semi-finite verbs and non-finite verbs. Coordination reduction leaves the coordinating conjunctions intact and this explains the presence of coordinators with all verb types, including dependent verbs. Coordination reduction creates verb forms that signal subject continuity but it does not create subject discontinuity forms and there is no switch-reference in South Wambon. However, the introduction of dependent subject continuity forms gives South Wambon speakers a choice in subject continuity conditions between dependent forms and independent verb forms. Since speakers prefer dependent forms under these conditions, a frequency pattern emerges that associates independent forms with subject discontinuity conditions and that sets the stage for the development of medial verb forms and switch-reference. North Wambon and Mandobo represent the second stage in which subject discontinuity forms develop. North Wambon transforms conjoined semi-finite independent verbs into two types of special medial verb forms that express switch-reference. In Mandobo any medially occurring independent verb form is reinterpreted as a Different Subject form. The two-stage hypothesis revives the coordination reduction theory of Haiman (1983a) as an explanation for the origin of (certain) switch-reference systems by viewing coordination reduction as an explanation of SS forms only. In this way, the two-stage theory overcomes the problems of limited applicability that Roberts (1997: 190) noted for the original theory of Haiman (1983a).