Thread:User talk:CodeCat/Balto-Slavic glottal stop/reply (9)

It is, because o and a merged in Balto-Slavic, and the "glottal stop" became a tonal feature. *mouʔros is a more "conservative" form, reflecting an earlier stage of PBS, but neither the Baltic nor the Slavic languages show any apparent distinction between o and a (the a in Slavic is in fact ā, and reflects a merger of earlier ō and ā, which did not happen in Baltic). Some reconstructions ascribe the merging of a and o to the individual dialects, but that doesn't explain why they merged in all the dialects; it's clearly either a common innovation of Balto-Slavic or a parallel innovation that happened in every Balto-Slavic dialect at the same time. If it's a parallel innovation, it could hardly have happened unless there was still a common dialect area among the various Balto-Slavic dialects, which implies they were still a common language. That in itself is not strange... the West Germanic languages show several parallel innovations that happened after they had become dialectally differentiated from Proto-Germanic.