Genetic ancestry of Hadza and Sandawe peoples reveals ancient population structure in Africa

Open access paper Genetic Ancestry of Hadza and Sandawe Peoples Reveals Ancient Population Structure in Africa, by Shriner, Tekola-Ayele, Adeyemo, & Rotimi, GBE (2018).

Abstract (emphasis mine):

The Hadza and Sandawe populations in present-day Tanzania speak languages containing click sounds and therefore thought to be distantly related to southern African Khoisan languages. We analyzed genome-wide genotype data for individuals sampled from the Hadza and Sandawe populations in the context of a global data set of 3,528 individuals from 163 ethno-linguistic groups. We found that Hadza and Sandawe individuals share ancestry distinct from and most closely related to Omotic ancestry; share Khoisan ancestry with populations such as ≠Khomani, Karretjie, and Ju/’hoansi in southern Africa; share Niger-Congo ancestry with populations such as Yoruba from Nigeria and Luhya from Kenya, consistent with migration associated with the Bantu Expansion; and share Cushitic ancestry with Somali, multiple Ethiopian populations, the Maasai population in Kenya, and the Nama population in Namibia. We detected evidence for low levels of Arabian, Nilo-Saharan, and Pygmy ancestries in a minority of individuals. Our results indicate that west Eurasian ancestry in eastern Africa is more precisely the Arabian parent of Cushitic ancestry. Relative to the Out-of-Africa migrations, Hadza ancestry emerged early whereas Sandawe ancestry emerged late.

Excerpts:

Introduction
In the Hadza population, the distribution of Y chromosomes includes mostly B2 haplogroups, with a smaller number of E1b1a haplogroups, which are common in Niger-Congo-speaking populations, and E1b1b haplogroups, which are common in Cushitic populations (Tishkoff, et al. 2007). In the Sandawe population, E1b1a and E1b1b haplogroups are more common, with lower frequencies of B2 and A3b2 haplogroups (Tishkoff, et al. 2007).

Conclusion
We found that Hadza ancestry diverged early, rather than late. We found evidence for contributions of Cushitic and Niger-Congo ancestries in Tanzania, consistent with the movements of herding and cultivating Cushitic speakers ~4,000 years ago and agricultural Niger-Congo speakers ~2,500 years ago (Newman 1995). However, we did not find evidence of a substantial contribution of Nilo-Saharan ancestry that might have resulted from movement of pastoralist Nilo-Saharan speakers (Newman 1995). We also identified west Eurasian ancestry in eastern and southern African populations more precisely as the Arabian parent of Cushitic ancestry. Finally, our ancestry analyses support the hypothesis that Omotic, Hadza, and Sandawe languages group together, rather than Omotic languages belonging to the Afroasiatic family and Hadza and Sandawe languages belonging to the Khoisan family.

I don’t like linguistic assumptions from admixture analysis; especially from scarce modern samples, as in this case.

Nevertheless, these papers may help clarify the different nature of Omotic and Cushitic among Afroasiatic languages, and thus leave the origin of Afroasiatic either:

a) To the east, with the traditionalist Afroasiatic – Semitic/Hamitic homeland association.

afroasiatic-homeland
Expansion of Afroasiatic

b) To the west, near modern Chadic languages (associated with the expansion of R1b-V88 subclades through a Green Sahara), as I suggested.

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