Southeast Africans and Chadians from Triska et al. 2015

Some other interesting things to note about this paper's new samples are the Southeast African and Chadian samples.

Some simple observations:

• The Samburu samples look to be highly Horn African-shifted. Their African and West Eurasian ancestry levels seem only a bit lower than those of the Somalis and Oromos. I suppose this implies that they have quite a bit of admixture from East/South Cushitic speakers. Something people have assumed long before genome sequencing, as far as I know... Their mtDNA lineages also implied such admixture, last I checked, so this makes some sense. It's just that the level of this admixture that's a bit surprising.

• The Turkana samples seem less Horn African-shifted than them but also seem to clearly have substantive admixture from Horn African Cushitic speakers who were probably quite genomically similar to modern Somalis. Again, this was somewhat expected and Tishkoff et al. 2009, albeit with less high-resolution data, ultimately indicated that Turkanas had such admixture anyway. Both them and the Samburus, despite being Nilo-Saharan speakers, are clearly mixtures between Nilotic speaking, Bantu speaking and Cushitic speaking Southeast Africans.

• The Daza Chadians are an intriguing case too. Despite being Nilo-Saharan speakers; they're clearly rich in West Eurasian ancestry. They're about as shifted toward West Eurasia & North Africa as Fulanis are (pulling about as eastward as they do in the PCA). The main difference, however, is that the Fulanis clearly seem like more of a mixture between West-Central Africans and Northwestern Africans whilst the Daza look to, mostly, be a mixture between the East African cluster and West Eurasians. [note]

• The Kanembu essentially just look like more West-Central African shifted versions of the Daza, understandably showing less of a pull toward the West Eurasians and North Africans as a result.

What I find most interesting about all of this are the Chadians, quite frankly. What's quite intriguing about their West Eurasian ancestry is that it, based on the ADMIXTURE results above, looks to be mainly derived from Northwestern African-related people (Mozabite-like peoples) as its mainly derived from the light blue cluster. This means they're basically some sort of East African version of the Fulani samples, especially in the Daza samples' case. They seem to lack the more Bedouin and Druze related affinities the Oromo, Somali, Nubian and Sudanese Arab groups are showing.

Although, they also differ from the Fulani samples in that they mostly don't show ancestry from the grey Sardinian peaking cluster. Their West Eurasian elements are wholly swallowed up by the light-blue Mozabite peaking cluster. I don't know what significance that might have but it's worth taking note of.

I really don't know much about Chad's history but I wonder if they used to be Chadic speakers? I'd be interested in seeing what sort of R1b-V88 frequencies these two populations have if anyone's seen Y-DNA data on them... Baqara Arabs (بقرة العرب) like the Messiria tribe seem to have notable R1b-V88 frequencies (see here) which, to me, implies some of their ancestors were Chadic speakers (like the Hausa) before their Arabization.

A Baqara Arab man and child riding cattle

Anyway, I'll leave any further theorizing and observations to future posts that will hopefully be based on new PCAs and perhaps also ADMIXTURE runs where these new samples will be run alongside the various other HSS samples out there.

References:

1. Extensive Admixture and Selective Pressure Across the Sahel Belt, Triska et al.