Early dialectal diversity in South Slavic II

Twenty years ago I discussed the oldest isoglosses in the South Slavic linguistic area (1982). Subscribing to Van Wijk’s view that the bundle of isoglosses which separates Bulgarian from Serbo-Croatian was the result of an early split in South Slavic and that the transitional dialects originated from a later mixture of Serbian and Bulgarian dialects when the contact between the two languages had been restored (1927), I argued that the shared innovations of Bulgarian and Serbo-Croatian must be dated to a period when the dialects were still spoken in the original Trans-Carpathian homeland of the Slavs. I concluded that there is no evidence for common innovations of South Slavic which were posterior to the end of what I have called the Late Middle Slavic period, which I dated to the 4th through 6th centuries AD. At that time, the major dialect divisions of Slavic were already established