The Siyom River Valley: An essay on intra-subgroup convergence in Tibeto-Burman

This paper has a fairly modest primary goal: to remove a question mark '?' which appears to the right of Galo (i.e., 'Gallong') in Sun's (1993; Sun 2003) provisional family tree of the Tani branch of Tibeto-Burman languages (Figure 1). The question mark appears in Sun's tree for a good reason: as he was compiling his masterful comparative-historical study of the Tani languages in the years leading up to 1993, most of the evidence available to Sun suggested aligning Galo genetically with Western Tani languages such as Hills Miri, Nyishi and Tagin. At the same time, though, Galo exhibited several features which were more characteristic of Eastern Tani languages such as Bori, Padam and Mising. At the time of Sun's writing, there was no obvious means of understanding why this should have been the case. The paper's second goal, then, will be to attempt to explain this situation on the basis of data and observations from the Western/Eastern Tani border areas obtained during 2008-2009.