Classification
The term 'narrow Bantu' was coined by the Benue–Congo Working Group to distinguish Bantu as recognized by Malcolm Guthrie in his seminal 1948 classification of the Bantu languages from Bantoid languages not recognized as Bantu by Guthrie (1948). In recent times, the distinctness of Narrow Bantu as opposed to the other Southern Bantoid groups has been called into doubt (cf. Piron 1995, Williamson & Blench 2000, Blench 2011), but the term is still widely used. A coherent classification of Narrow Bantu will likely need to exclude many of the Zone A and perhaps Zone B languages.
There is no genealogical classification of the (Narrow) Bantu languages. The most widely used system, the alphanumeric coding system developed by Guthrie, is mainly geographic. However, based on reflexes of proto-Bantu tone patterns, zones A–C and part of D are grouped together as Northwest Bantu (or Forest Bantu), and zones D–S as Central Bantu (or Savanna Bantu). Northwest Bantu is more divergent internally than Central Bantu, and perhaps less conservative due to contact with non-Bantu Niger–Congo languages; however, Central Bantu is likely the innovative line cladistically, with Northwest being the non-Central languages, not a family in their own right. Most attempted classifications are problematic as they consider only languages which happen to fall within traditional Narrow Bantu, rather than South Bantoid, which has been established, as a whole.
The only attempt at a detailed genetic classification to replace the Guthrie system is the 1999 "Tervuren" proposal of Bastin, Coupez, and Mann. However, it relies on lexicostatistics, which, because it relies on similarity, rather than shared innovations, can lead to grouping together conservative languages which are not closely related. Meanwhile, Ethnologue has added languages to the Guthrie classification that Guthrie overlooked, while removing the Mbam languages (much of zone A), and shifting some languages between groups (much of zones D and E to a new zone J, for example, and part of zone L to K, and part of M to F) in an apparent effort at a semi-genetic, or at least semi-areal, classification. However, zone S (Southern Bantu) does appear to be a coherent group. The languages which share Dahl's Law may also form a valid group, Northeast Bantu. The infobox at right lists these together with various low-level groups that are fairly uncontroversial, though they continue to be revised. The development of a rigorous genealogical classification of many branches of Niger–Congo, not just Bantu, is hampered by insufficient data.
Read more about this topic: Bantu Languages