The author applies the comparative method for the reconstruction of earlier aspectual systems in the Afro-Asiatic phylum of languages. Moving `upstream' from the documented systems of Semitic, Berber and Old Cushitic the state of affairs during the common stage of Proto-Semito-Berbero-Cushitic is reconstructed. With the addition of Egyptian and Chadic data important conclusions regarding the elusive Proto-Afro-Asiatic are reached. Moving `downstream' the trajectory of individual aspectual systems through their later stages is analyzed. A central piece of the monograph is the reconstruction of intermediate stages reflecting the long-term developments of aspectual and temporal categories of individual languages from the Old towards their Middle periods. The continuity and innovation in the aspectual systems towards the contemporary state of affairs in analytic (serial) constructions of Modern Aramaic and Arabic vernacular languages is explicated. The author demonstrates that it is imperative to work in a larger typological framework and that in the field of Afro-Asiatic linguistics valuable insights can be gained from the study of parallel phenomena in Indo-European languages. At the same time, Indo-Europeanists will profit from the study of typologically earlier aspect-prominent systems of Afro-Asiatic languages. The monograph offers important contributions to our understanding of universals and to the typology and diachrony of tense and aspect.