The Chadic language family in the Central Sudan is comparable to a landscape the surface of which consists of plains, valleys and mountain ridges. Some areas were more resistant than others against the forces of erosion. Different degrees of hardness and resistibility caused languages to preserve or reduce the original substance with regard to lexicon or grammar of an individual language or the entire language group. Chadic with its ca. 130–150 languages is probably the one branch of Hamitosemitic (Afroaasiatic) which has been subject to the strongest transformational processes in which erosion, i.e., attrition of language material in space and time, played a dominant role. The paper presents numerous examples illustrating different stages of progressive erosion which may characterize the nature of Chadic linguistic history.