Is Malayo-Polynesian a primary branch of Austronesian?

An understudied morphosyntactic innovation, reanalysis of the Proto-Austronesian (PAn) stative intransitive prefix *ma- as a transitive affix, offers new insights into Austronesian higher-order subgrouping. Malayo-Polynesian is currently considered a primary branch of Austronesian, with no identifiably closer relationship with any linguistic subgroup in the homeland (Blust 1999, 2009/2013; Ross 2005). However, the fact that it displays the same innovative use of ma- with Amis, Siraya, Kavalan and Basay-Trobiawan and shares the merger of PAn *C/t with this group suggests that Malayo-Polynesian and East Formosan may share a common origin – the subgroup that comprises the four languages noted above. This observation points to a revised subgrouping more consistent with a socio-historical picture where the out-of-Taiwan population descended from a seafaring community expanding to the Batanes and Luzon after having developed a seafaring tradition. It also aligns with recent findings in archaeology and genetics that (i) eastern Taiwan is the most likely starting point of Austronesian dispersal (Hung 2005, 2008, 2019; Bellwood 2017; Bellwood & Dizon 2008; Carson & Hung 2018) and (ii) that the Amis bear a significantly closer relationship with Austronesian communities outside Taiwan (Capelli et al. 2001; Trejaut et al. 2005; McColl et al. 2018; Pugach et al. 2021; Tätte et al. 2021). Future investigation of additional shared innovations between Malayo-Polynesian and East Formosan could shed further light on their interrelationships.