The Nilo-Saharan languages are a proposed family of African languages spoken by some 50 million people, mainly in the upper parts of the Chari and Nile rivers, including historic Nubia, north of where the two tributaries of the Nile meet. The languages extend through 17 nations in the northern half of Africa: from Algeria to Benin in west; from Libya to the Democratic Republic of the Congo in the center; and from Egypt to Tanzania in the east. Eight of its proposed constituent divisions (excluding Kunama, Kuliak, and Songhay) are found in the modern nation of Sudan, through which the Nile River flows. As indicated by its hyphenated name, Nilo-Saharan is a family of the African interior, including the greater Nile basin and the central Sahara desert. Joseph Greenberg named the group and argued it was a genetic family in his 1963 book The Languages of Africa. It contains the languages not included in the Niger–Congo, Afroasiatic, or Khoisan families. It has not been demonstrated that the Nilo-Saharan languages constitute a valid genetic grouping, and linguists have generally seen the phylum as “Greenberg’s wastebasket”, into which he placed all the otherwise unaffiliated non-click languages of Africa. Its supporters accept that it is a challenging proposal to demonstrate, but contend that it looks more promising the more work is done. Some of the constituent groups of Nilo-Saharan are estimated to predate the African neolithic. Thus, the unity of Eastern Sudanic is estimated to date to at least the 5th millennium BC. Nilo-Saharan genetic unity would necessarily be much older still and date to the late Upper Paleolithic. Glottolog (2013) does not accept a relationship between any of the Nilo-Saharan families, nor the unity of Eastern Sudanic.