Chapter 6 is a short outlook on feasible and necessary follow-up comparative research projects towards solid reconstructions of the other branches of Chadic besides Central Chadic, not least in order to arrive at a robust reconstruction of Proto-Chadic as a whole. Further, the list of petrified morphological markers provides a starting point for reconstructing their original functions based on a comparative analysis of their synchronic functions in the modern Chadic languages. We would also want a fairly complete collection of isogloss maps for words and linguistic features for Central Chadic and later also for the other branches of the Chadic language family.

Chapter 5 looks at hidden reflexes of Proto-Afroasiatic language features in Central Chadic which have hitherto largely gone unnoticed. These are in particular the fundamental root-and-pattern structure, the relatively high frequency of triradical roots, the structural relevance of ‘weak radicals’ that function as both consonants and high vowels, the sporadic local emergence of synchronic glottalised consonants, the synchronic presence but historical absence of prenasalised obstruents, the high frequency of the reconstructable polyfunctional prefix *{ma-}, and the remnants of a set of determiners as reconstructed for Proto-Chadic by Schuh (1983).

Chapter 3 discusses the major diachronic processes affecting Central Chadic languages, starting with the massive deletion of reconstructed segments. It explains the historical coming about of prosodies through desegmentalisation and prosodification when coarticulatory features become floating and reassociate with other segments in the chain of segments. It describes the frequent occurrence of at times multiple consonantal metathesis. Historical sound changes are then identified and described in great detail as reflecting both ‘natural’ and contact-induced sound changes. Finally, the chapter discusses compensatory strategies for historically lost segmental material of roots.

Chapter 4 looks in detail at selected issues of historical Central Chadic phonology, by first of all confronting hypotheses about regular ‘natural’ vs. sporadic ‘contact-induced’ sound changes. It then discusses at some length the vocalogenesis scenario by which a minimal vowel system becomes massively enriched via phonologisation of allophones and variants of reconstructed vowels and approximants. The chapter than discusses canonical root shapes and the potential functionality of root types, not least in the light of different sound changes affecting different root types. It then looks in some detail at the various markers that are used as root-augmental material, including a discussion of potential circumfix marking in the proto-language. It then introduces the hitherto neglected prosodies of ‘glottalisation’ and obstruent ‘prenasalisation’ and their historical origins in the proto-language. It concludes by discussing alternative diphthong and monophthong word endings.

Chapter 2 introduces the peculiar features that can be reconstructed for the vocal domain in Proto-Central Chadic, being made up of both vowels (*/a/, *ə) and the conditioned allophones [i] and [u] of the approximants */y/ and */w/. It then presents the reconstructed segments in terms of vowels, approximants, and consonants. It discusses the problematic phonetic nature of ‘schwa’ and its varying transcriptions. Root-and-pattern structure is then introduced, followed by a description of the diachronic process of root augmentation through petrified/fused morphological markers. Lastly, types and diachronic sources of ‘prosodies’ are described as ‘floating’ dis- and reassociated coarticulation features of segments.

The first, introductory, chapter explains the poor state of Chadic comparative linguistics and motivates the present study against the backdrop of previous research. It outlines the frames of reference and limitations of the study and justifies the double approach of multilateral comparative and micro-level dialectological analysis and comparison of data. It illustrates the spread of lexical innovations by reference to a set of schematic maps of isoglosses. Different formats of data representation are related to different levels of analysis. The structure of the book is outlined.