quality:corruption, information:classification
Characteristics

The constituent families of Nilo-Saharan are quite diverse. One characteristic feature is a tripartite singulative–collective–plurative number system, which Blench (2010) believes is a result of a noun-classifier system in the protolanguage. The distribution of the families may reflect ancient watercourses in a green Sahara during the African humid period before the 4.2-kiloyear event, when the desert was more habitable than it is today.