There is no consensus regarding the exact location of the Proto-Cushitic homeland; Christopher Ehret hypothesizes that it may have originated in the Red Sea Hills.
[3][4] Christopher Ehret argues for a unified Proto-Cushitic language in the Red Sea Hills as far back as the Early Holocene.
Ehret notes that in particular the affricates *ts, *dz, and the velar nasals *ŋ, *ŋʷ rely on fairly little evidence, and that *p, *pʼ are difficult to distinguish from other consonants in the comparative material; these are shown on a darker background above.
A system given by Appleyard[9] as "widely accepted" excludes these questioned segments, but includes *tʃ, *dʒ and a contrast of *ɗ and *tʼ.
[12][a] Major conditional sound laws involve palatalization, especially in all Somaloid languages as well as Oromo, and several simplifications of consonant clusters.
Appleyard[13] does not posit any glottalized consonants for Proto-Agaw, and reconstructs uvular *q, *qʷ for sound correspondences of /kʼ/, /kʼʷ/ in Bilin, respectively, with e.g. /χ/, /χʷ/ or /q/, /qʷ/ in the rest of the subfamily.
Further instances of long vowels arise in many languages through the vocalization of the laryngeal consonants *ħ, *ʕ, *h, *ʔ and monophthongization of the combinations *ay, *ey, *aw.