the spread of agriculture, the spread of pastoralism, and the dispersal of affiliated language groups and genetic lineages. It is important to note, however, that these associations among linguistic, archaeological, and genetic data are not presented here to paint a simple picture of migration or replacement, but rather to illustrate that large-scale movements of technology and culture have resulted in detectable amounts of gene flow among the involved peoples and that the interpretation of extant genetic patterns benefits from an understanding of the combined data.
Approximately 14 kya, climatic changes associated with the end of the Last Glacial Maximum resulted in regions around the world becoming more favorable to human exploitation. Northern Africa is one such region, and ~13 kya, novel technologies (“Natufian”) thought to be the immediate precursor to agricultural technologies emerged and were associated with semisedentary subsistence and population expansions in northeastern Africa (Bar-Yosef, 1987). Moreover, before the emergence of the Natufian-styled artifacts, the archaeological record includes two artifact styles, the “Geometric Kebaran” and the “Mushabian” associated with Middle Eastern and Northern African populations, respectively (Bar-Yosef, 1987). The archaeological evidence suggests the peoples using these assemblages interacted for well over 1,000 years, and linguistic evidence suggests that the peoples using these assemblages may have spoken some form of proto-Afroasiatic (Bar-Yosef, 1987; Ehret et al., 2004). Although the origins of the Afroasiatic language family remain contentious, linguistic data generally support a model in which the Afroasiatic language family arose in Northern Africa >10 kya (Ehret et al., 2004). Moreover, analyses of the Cushitic branch of the Afroasiatic language family suggest that proto-Cushitic arose and diversified at least 7 kya, and this likely took place in Ethiopia (Ehret, 1979).
Intriguingly, the origin and diversification of proto-Afroasiatic is consistent with the spread of intensive plant collection in the archaeological record, and some interpret this pattern to represent a model in which proto-Afroasiatic speakers developed the novel subsistence technology resulting in the expansion and spread of their Afroasiatic descendants in the region (Ehret, 1979). Some examples of the relevant linguistic data include reconstructed Chadic root words for “porridge” and “sorghum” and the Cushitic root words for “grain” and “wheat” (Ehret, 1979). Because these and other root words are present in many of the Chadic and Cushitic languages, it is assumed that they were present in the proto-Chadic and proto-Cushitic languages and therefore must be as old as those proto-languages (Ehret, 1979).