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View Full Version : Tales of Human Migration, Admixture, and Selection in Africa (Schlebusch, 2018)



Angoliga
06-05-2018, 10:31 PM
Annual Review of Genomics and Human Genetics - Vol. 19: (Volume publication date August 2018)

Review in Advance first posted online on May 4, 2018 (https://www.annualreviews.org/doi/abs/10.1146/annurev-genom-083117-021759?journalCode=genom). (Changes may still occur before final publication.)




Abstract:


In the last three decades, genetic studies have played an increasingly important role in exploring human history. They have helped to conclusively establish that anatomically modern humans first appeared in Africa roughly 250,000–350,000 years before present and subsequently migrated to other parts of the world. The history of humans in Africa is complex and includes demographic events that influenced patterns of genetic variation across the continent. Through genetic studies, it has become evident that deep African population history is captured by relationships among African hunter–gatherers, as the world’s deepest population divergences occur among these groups, and that the deepest population divergence dates to 300,000 years before present. However, the spread of pastoralism and agriculture in the last few thousand years has shaped the geographic distribution of present-day Africans and their genetic diversity. With today’s sequencing technologies, we can obtain full genome sequences from diverse sets of extant and prehistoric Africans. The coming years will contribute exciting new insights toward deciphering human evolutionary history in Africa.




... Regarding potential Afroasiatic origins and expansions:

It is currently believed that farming practices in northeastern and eastern Africa developed independently in the Sahara/Sahel (around 7,000 BP) and the Ethiopian highlands (7,000–4,000 BP), while farming in the Nile River Valley developed as a consequence of the Neolithic Revolution in the Middle East (84). Northeastern and eastern African farmers today speak languages from the Afro-Asiatic and Nilo-Saharan linguistic groups, which is also reflected in their genetic affinities (Figure 3, K=6). In the northern parts of East Africa (South Sudan, Somalia, and Ethiopia), Nilo-Saharan and Afro-Asiatic speakers with farming lifeways have completely replaced hunter–gatherers. It is still largely unclear how farming and herding practices influenced the northeastern African prefarming population structure and whether the spread of farming is better explained by demic or cultural diffusion in this part of the world. Genetic studies of contemporary populations and aDNA have started to provide some insights into population continuity and incoming gene flow in this region of Africa.


a) Demographic model of African history and estimated divergences,
b) K5 ADMIX
https://i.imgur.com/mu24Jw2.png


Population split times, hierarchy, and population sizes (summarized from 123). Horizontal width represents population size; horizontal colored lines represent migrations, with down-pointing triangles indicating admixture into another group. (b) Population structure analysis at 5 assumed ancestries (K=5) for 93 African and 6 non-African populations. Non-Africans (brown), East Africans (blue), West Africans ( green), central African hunter–gatherers (light blue), and Khoe-San (red ) populations are sorted according to their broad historical distributions.


Supplemental Fig 1) Routes of the Bantu expansion according to archaeology (left) and linguistics (right):

https://i.imgur.com/cS6VzvY.png

Red arrows indicate possible routes and origin of the Western Bantu-speakers and blue arrows indicate possible routes and origins of Eastern Bantu-speakers. The central African rainforest area is highlighted in green. The
archaeology map was adapted and redrawn from Mitchell and Lane, 2013 (9).