More than forty years ago, Joseph Greenberg (1963) demonstrated that the African continent can be divided into four distinct genetic phyla, or families as he called them, namely Niger-Congo (or Kongo-Kordofanian), Nilo-Saharan, Afroasiatic, and Khoisan. For subsequent generations of Africanists, this classification has served as a reference system to describe the relationship patterns among African languages. In this tradition, scholars doing comparative work on African languages were preoccupied to quite some extent with reconstructing and understanding similarities across languages with reference to genetic parameters. One effect this line of research had was that an interest in other kinds of linguistic relationship was never really pronounced. Especially the question of whether, or to what extent, structural similarities and dissimilarities among African languages are the result of areal, that is contact-induced relationship, has never attracted any major research activities beyond individual studies dealing with lexical borrowing and related subjects. Whether the African continent constitutes an areally defined unit, or whether it can be subclassified into linguistic areas (or sprachbunds, or convergence areas) remained issues that were the subject of casual observations or conjecture, or both, but not really of more detailed research.

Still, once more it was Greenberg who drew attention to the importance of areal relationship in Africa.