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Ancient Tanzanian Pastoralist results... VERY interesting stuff!
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[QUOTE]Originally posted by Doug M: [QB] Just note that most "Africa wide" studies of DNA omit populations in the Sahel, including the Fulani, the populations of Southern Algeria, Northern Mali, Mauritania, Northern Sudan and so forth. And when they do study the DNA of these populations, they are treated as a "distinct group" of their own, in other words, not included in North Africa and not included as "Sub Saharan". Just more games being played with the data..... [QUOTE] Understanding human genetic diversity in Africa is important for interpreting the evolution of all humans, yet vast regions in Africa, such as Chad, remain genetically poorly investigated. Here, we use genotype data from 480 samples from Chad, the Near East, and southern Europe, as well as whole-genome sequencing from 19 of them, to show that many populations today derive their genomes from ancient African-Eurasian admixtures. We found evidence of early Eurasian backflow to Africa in people speaking the unclassified isolate Laal language in southern Chad and estimate from linkage-disequilibrium decay that this occurred 4,750–7,200 years ago. It brought to Africa a Y chromosome lineage (R1b-V88) whose closest relatives are widespread in present-day Eurasia; we estimate from sequence data that the Chad R1b-V88 Y chromosomes coalesced 5,700–7,300 years ago. This migration could thus have originated among Near Eastern farmers during the African Humid Period. We also found that the previously documented Eurasian backflow into Africa, which occurred ∼3,000 years ago and was thought to be mostly limited to East Africa, had a more westward impact affecting populations in northern Chad, such as the Toubou, who have 20%–30% Eurasian ancestry today. We observed a decline in heterozygosity in admixed Africans and found that the Eurasian admixture can bias inferences on their coalescent history and confound genetic signals from adaptation and archaic introgression. [b]African genetic diversity is still incompletely understood, and vast regions in Africa remain genetically undocumented. Chad, for example, makes up ∼5% of Africa’s surface area, and its central location, connecting sub-Saharan Africa with North and East Africa, positions it to play an important role as a crossroad or barrier to human migrations. However, Chad has been little studied at a whole-genome level, and its position within African genetic diversity is not well known. With 200 ethnic groups and more than 120 indigenous languages and dialects, Chad has extensive ethnolinguistic diversity.1 It has been suggested that this diversity can be attributed to Lake Chad, which has attracted human populations to its fertile surroundings since prehistoric times, especially after the progressive desiccation of the Sahara starting ∼7,000 years ago (ya).[/b] Important questions about Africa’s ethnic diversity are the relationships among the different groups and the relationships between cultural groups and existing genetic structures. In the present study, we analyzed four Chadian populations with different ethnicities, languages, and modes of subsistence. Our samples are likely to capture recent genetic signals of migration and mixing and also have the potential to show ancestral genomic relationships that are shared among Chadians and other populations. An additional major question relates to the prehistoric Eurasian migrations to Africa: what was the extent of these migrations, how have they affected African genetic diversity, and what present-day populations harbor genetic signals from the ancient migrating Eurasians? [b]We have previously reported evidence of gene flow from the Near East to East Africa ∼3,000 ya, as well as subsequent selection in Ethiopians on non-African-derived alleles related to light skin pigmentation.[/b] snip Multiple Eurasian Admixtures in Africa after 6,000 ya [b]We have previously reported massive gene flow ~3,000 ya from Eurasians to Ethiopian populations.4 Here, we reassess the presence of Eurasian ancestry in Africa by using f3 statistics25 in the form of f3:X; Eurasian, Yoruba, where a negative value with a Z score < -4 indicates that X is a mixture of Africans and Eurasians. We found, as expected, that most Ethiopians are a mixture of Africans and Eurasians. An exception is the Gumuz population, where f3: Gumuz; Eurasian, Yoruba is always positive. The Gumuz language belongs to the Nilo-Saharan family, which could have isolated the Gumuz from the Afro-Asiatic-speaking Ethiopians. However, we found that the Toubou in Chad, who also speak a Nilo-Saharan language, are a mixture of Africans and Eurasians, making f3:Toubou; Eurasian, Yoruba always significantly negative. This suggests that the impact of Eurasian migrations today extends beyond East Africa and the Afro-Asiatic-speaking populations.[/b] [/QUOTE] http://www.sciencedirect.com/science/article/pii/S0002929716304487 [IMG]https://ars.els-cdn.com/content/image/1-s2.0-S0002929716304487-gr3.jpg[/IMG] They say they have little DNA from Chad and other African populations but they are quick to claim that "Eurasians" migrated all the way into Central Africa? Seriously? Where are the other surrounding African populations included as part of this study? Note the primary populations used for comparison: Yoruba (the so called pure sub saharans reference population used in most of these studies), Ethiopians like the Ahmara and then they go way off to Greece and Turkey. No Fulani included, No Tuareg included. No Northern Nigerians included, No populations in Niger included. No Sudanese (Beja, "nubians", Darfurians, Nuer, Dinka, etc). No populations surrounding Chad were included. But this is the game they play with all these papers. By now any Africa wide genomic study should inclcude ALL populations of Africa not certain hand picked populations used over and over again. And not to mention lets not talk about any DNA from ancient remains in Chad compared to moderns... which is standard for most of these types of DNA studies, except in Africa. Of course they will claim that they cant find any ancient sites and remains in Chad for whatever reason. [/QB][/QUOTE]
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