The Niger-Congo noun class system has resisted historical reconstruction due to the advanced stage of grammaticalisation its markers present. Yet, incipient systems of alternative nominal classification such as numeral classifiers and class-terms found across various branches of Niger-Congo provide, by virtue of their cognitive transparency, a key to the identification of both the ultimate lexical sources and the syntactic structures from which the ancient Niger-Congo noun class system must have developed. After an overview of the properties of the Niger-Congo noun class system (Section 2), Section 3 examines alternative systems of nominal classification such as numeral classifiers (3.1) and class-terms (3.2). The synthesis (Section 4) provides a model of the emergence of the Niger-Congo noun class system and its morphological exponents from nouns for basic level concepts, body parts and social functions which were used as head nouns in associative constructions or as class-terms in compounds.