Internal Relationships
Dimmendaal (2008) notes that Greenberg (1963) based his conclusion on sound evidence, and that the proposal as a whole has become more convincing in the decades since. Mikkola (1999) reviewed Greenberg's evidence and found it convincing. Roger Blench notes morphological similarities in all putative branches, which leads him to believe that the family is likely to be valid.
Koman and Gumuz, however, are poorly known, and have been difficult to evaluate until recently. Songhai is markedly divergent, probably due to massive influence from the Mande languages. Also problematic are the Kuliak languages, which are spoken by hunter-gatherers and appear to retain a non-Nilo-Saharan core; Blench believes they may have been similar to Hadza or Dahalo and shifted incompletely to Nilo-Saharan.
Dimmendaal (who had originally supported their inclusion) believes the Kadu languages form a small family of their own. Anbessa Tefera and Peter Unseth consider the poorly attested Shabo language to be Nilo-Saharan, though unclassified within the family due to lack of data; Dimmendaal considers it to be a language isolate on current evidence. Proposals have sometimes been made to add Mande (usually included in Niger–Congo), largely due to its many noteworthy similarities with Songhay rather than with Nilo-Saharan as a whole.
The extinct Meroitic language of ancient Kush has been accepted by linguists such as Rille, Dimmendaal, and Blench as Nilo-Saharan, though others argue for an Afroasiatic affiliation. It is poorly attested.
There is little doubt that the constituent families of Nilo-Saharan—of which only Eastern Sudanic and Central Sudanic show much internal diversity—are valid groups. However, there have been several conflicting classifications in grouping them together. Each of the proposed higher-order groups has been rejected by other researchers: Greenberg's Chari–Nile by Bender and Blench, Bender's Core Nilo-Saharan by Dimmendaal and Blench, and Ehret's Sahelian etc. by everyone. What remains are eight (Dimmendaal) to twelve (Bender) constituent families of no consensus arrangement.
Read more about this topic: Nilo-Saharan Languages
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