African population history: an ancient DNA perspective
Aug. 17, 2021
Ancient DNA in North Africa
In North Africa, modern-day groups are largely related to Eurasian and Middle Eastern populations, with very low levels of genetic contributions from sub-Saharan Africa. A debate existed whether this was the result of Paleolithic back-to-Africa migrations, or migrations connected to the introduction of farming practices to North Africa during the Neolithic. A study on 15 kya old remains from Morocco demonstrated that Northern Africa received significant amounts of gene-flow from Eurasia predating the Holocene and development of farming practices. aDNA studies further found that Early Neolithic North Africans (∼7 kya) trace their ancestry to these Paleolithic North African groups, while Late Neolithic groups (∼5 kya) contained an Iberian component, indicating trans-Gibraltar gene-flow. These two different signals in Early and Late Neolithic individuals, indicate that the spread of farming practices in North Africa involved both the movement of ideas and people.
The Sahara poses a geographic barrier to human migration, aside from intermittent greening periods. Studies on modern-day populations and aDNA from Egyptian mummies indicated that gene-flow from the south, across the Sahara into modern-day North Africans, were low and appeared in recent times. More ancient individuals from Morocco, however, seem to have had higher affinities to sub-Saharan Africans. The Paleolithic (15 kya) and Early Neolithic (7 kya) individuals lived before and during the most recent Green Sahara period (stretching from 12 kya to 5 kya), and yet they have similar genetic compositions with similar affinities to sub-Saharan Africa, while modern-day North Africans have very little sub-Saharan African contribution. Consequently the cycling of the Sahara through its wet and dry phases seems to have had an influence on amount of gene-flow between North and Sub-Saharan Africa, although the exact dynamics of those migrations needs to be further investigated, ideally through genome-wide aDNA studies.