In unsupervised ADMIXTURE analysis, one usually gets a division in Africa between three major components:
1. A West African centered one (Yoruba, Mandinka)
2. An East African one (Maasai)
3. A Fertile Crescent one (most Egypt, part of Ethiopia)
Two of them derive from well known local wholly or at least mostly independent Neolithic components Revolutions: the West African one (with its own special tropic adapted plants) and the Fertile Crescent one.
The mystery is about the quite widespread "East African", Maasai centred one. Is it a third Neolithic Revolution (fourth with the Malagasy migration) affecting Africa? Is it simply an ancient stable mix of the former two, mistaken by ADMIXTURE for an "unadmixed" component?
I'll be running some experiments trying to find clues about this. Then I'll return to Europe and the Middle East and speculate on what exactly are those "Subsaharan African" segments about...