Underlying low tones in Ruwund

In this paper the author examines data from Ruwund, a language with surface tone patterns often the reverse of those reconstructed for ProtoBantu, and proposes that, whereas most contemporary Bantu languages are believed to have tonal systems based on an underlying high/toneless contrast, Ruwund is based on a low/toneless contrast. Rules of tone spread and deletion apply to low tones rather than high tones, and the "default low insertion" rule of other languages is replaced in Ruwund by a rule adding default high tones. This finding is theoretically significant in that it contradicts Pulleyblank's [1986] proposal that "low" is always the default value in a two-tone language