Eurasian backflow

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The term Eurasian backflow, or Eurasian back-migrations, has been used to describe several pre-Neolithic and Neolithic migration events of humans from western Eurasia back to Africa. [1]

Pre-Neolithic and Neolithic migration events in Africa. Pre-Neolithic and Neolithic migration events in Africa (excluding Basal-West-Eurasian geneflow during the Paleolithic).jpg
Pre-Neolithic and Neolithic migration events in Africa.

Homo sapiens had left Africa about 70-50,000 years ago, [3] [4] [5] and between 30,000-15,000 years ago migrated back from the Middle East into Northern Africa. About 3,000 years ago, [6] [7] or already earlier between 6,000-5,000 years ago, [8] farmers from Anatolia and the Near East migrated into the Horn of Africa. Signs of this migration can be found in the genomes of contemporary peoples from all over East Africa. [1] [9] Next to Eastern Africa, significant Eurasian ancestry is found in Northern Africa, and among specific ethnic groups of the Horn of Africa, as well as among the Malagasy people of Madagascar. Various genome studies found also evidence for multiple pre-historic back-migrations from various Eurasian populations and subsequent admixture with native groups. [10] West-Eurasian geneflow arrived to Northern Africa during the Paleolithic, followed by other Neolithic migration events. [6] Genetic data on the Taforalt samples "demonstrated that Northern Africa received significant amounts of gene-flow from Eurasia predating the Holocene and development of farming practices". [11] Medieval geneflow events, such as the Arab expansion also left traces in various African populations, but with Neolithization having a much larger demographic impact than Arabization. [12]

Map of major prefarming population stratification across the African continent. Map of major prefarming population stratification across the African continent.jpg
Map of major prefarming population stratification across the African continent.

The people migrating back to Africa were closely related to the Neolithic farmers who had brought agriculture from the Near East to Europe about 7,000 years ago. This population is also closely related to present-day Sardinians, [1] although studies have made distinctions between the population that brought farming into Europe, and the Levantine related groups that spread southward into East Africa. [14] A study from 2020 inferred two sources for the spread of Eurasian admixture in Northeastern Africa, with one associated with pastoralism. The initial phase involved groups originating from the Levant and North Africa that gave rise to the Pastoral Neolithic. [15] Further research has shown that the back-migration into the region was a complex process, identifying multiple origins for the Eurasian component in Northeast African groups today. [16] [17]

A report in November 2015 on a 4,500-year-old Ethiopian genome [18] [19] had originally overestimated the genetic influence of the Eurasian backflow, claiming that signs of the migration could be found in genomes all over Africa. This mistaken claim was based on a data-processing error and was corrected in February 2016. The West Asian admixture was only predominant in the populations of the Horn of Africa, in particular Ethiopian highlanders, and less relevant or absent in the genetic makeup of West and Central Africans. [9]

Neanderthal admixture and Eurasian ancestry

In 2016, researchers recognized that the Neanderthal ancestry in African populations, strongly corresponds with the levels of Western Eurasian ancestry. The geneticists elaborated that: "Neanderthal ancestry is not expected in Africa, yet today many Africans carry Neanderthal-derived alleles. The plot shows that the Neanderthal ancestry proportion in Africans is correlated with gene flow from Eurasians. For example, knowing that today Eurasians carry ∼2% of Neanderthal ancestry, we observed that East Africans (Ethiopians) had ∼1% Neanderthal ancestry and ∼50% Eurasian ancestry. Correspondingly, Near Easterners showed a decline in Neanderthal ancestry proportional to their levels of African ancestry." [20]

Chen, Lu's publication found back-migrations contributed to the signal of Neanderthal ancestry in Africans. Data indicated that back-migrations giving Neanderthal sequences came after the split of Europeans and East Asians, from populations related to the European lineage. The overlap of this ancestral European ancestry and Neanderthal segments was highly significant. [21]

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<span class="mw-page-title-main">Western hunter-gatherer</span> Archaeogenetic name for an ancestral genetic component

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<span class="mw-page-title-main">Ancient Southern East Asian</span> Archaeogenetic name for an ancestral genetic component

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References

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  2. ↑ Vicente, Mário; Schlebusch, Carina M (2020-06-01). "African population history: an ancient DNA perspective". Current Opinion in Genetics & Development. Genetics of Human Origin. 62: 8–15. doi: 10.1016/j.gde.2020.05.008 . ISSN   0959-437X. PMID   32563853. S2CID   219974966.
  3. ↑ Posth C, Renaud G, Mittnik M, Drucker DG, Rougier H, Cupillard C, et al. (2016). "Pleistocene Mitochondrial Genomes Suggest a Single Major Dispersal of Non-Africans and a Late Glacial Population Turnover in Europe". Current Biology. 26 (6): 827–833. Bibcode:2016CBio...26..827P. doi:10.1016/j.cub.2016.01.037. hdl: 2440/114930 . PMID   26853362. S2CID   140098861.
  4. ↑ Karmin M, Saag L, Vicente M, Wilson Sayres MA, Järve M, Talas UG, et al. (April 2015). "A recent bottleneck of Y chromosome diversity coincides with a global change in culture". Genome Research. 25 (4): 459–66. doi:10.1101/gr.186684.114. PMC   4381518 . PMID   25770088.
  5. ↑ Haber M, Jones AL, Connell BA, Arciero E, Yang H, Thomas MG, et al. (August 2019). "A Rare Deep-Rooting D0 African Y-Chromosomal Haplogroup and Its Implications for the Expansion of Modern Humans Out of Africa". Genetics. 212 (4): 1421–1428. doi:10.1534/genetics.119.302368. PMC   6707464 . PMID   31196864.
  6. 1 2 Pickrell, Joseph K.; Patterson, Nick; Loh, Po-Ru; Lipson, Mark; Berger, Bonnie; Stoneking, Mark; Pakendorf, Brigitte; Reich, David (2014-02-18). "Ancient west Eurasian ancestry in southern and eastern Africa". Proceedings of the National Academy of Sciences of the United States of America. 111 (7): 2632–2637. arXiv: 1307.8014 . Bibcode:2014PNAS..111.2632P. doi: 10.1073/pnas.1313787111 . ISSN   0027-8424. PMC   3932865 . PMID   24550290.
  7. ↑ Haber, Marc; Mezzavilla, Massimo; Bergström, Anders; Prado-Martinez, Javier; Hallast, Pille; Saif-Ali, Riyadh; Al-Habori, Molham; Dedoussis, George; Zeggini, Eleftheria; Blue-Smith, Jason; Wells, R. Spencer; Xue, Yali; Zalloua, Pierre A.; Tyler-Smith, Chris (December 2016). "Chad Genetic Diversity Reveals an African History Marked by Multiple Holocene Eurasian Migrations" (PDF). The American Journal of Human Genetics. 99 (6): 1316–1324. doi:10.1016/j.ajhg.2016.10.012. PMC   5142112 . PMID   27889059. S2CID   38169172.
  8. ↑ Vicente, Mário; Schlebusch, Carina M (2020-06-01). "African population history: an ancient DNA perspective". Current Opinion in Genetics & Development. Genetics of Human Origin. 62: 8–15. doi: 10.1016/j.gde.2020.05.008 . ISSN   0959-437X. PMID   32563853. S2CID   219974966.
  9. 1 2 Callaway, Ewen (29 January 2016). "Error found in study of first ancient African genome". Nature. doi:10.1038/nature.2016.19258.
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  11. ↑ van de Loosdrecht, Marieke; Bouzouggar, Abdeljalil; Humphrey, Louise; Posth, Cosimo; Barton, Nick; Aximu-Petri, Ayinuer; Nickel, Birgit; Nagel, Sarah; Talbi, El Hassan; El Hajraoui, Mohammed Abdeljalil; Amzazi, Saaïd; Hublin, Jean-Jacques; Pääbo, Svante; Schiffels, Stephan; Meyer, Matthias (2018-05-04). "Pleistocene North African genomes link Near Eastern and sub-Saharan African human populations". Science. 360 (6388): 548–552. Bibcode:2018Sci...360..548V. doi: 10.1126/science.aar8380 . ISSN   0036-8075. PMID   29545507. S2CID   206666517.
  12. ↑ Serra-Vidal, Gerard; Lucas-Sanchez, Marcel; Fadhlaoui-Zid, Karima; Bekada, Asmahan; Zalloua, Pierre; Comas, David (2019-11-18). "Heterogeneity in Palaeolithic Population Continuity and Neolithic Expansion in North Africa". Current Biology. 29 (22): 3953–3959.e4. Bibcode:2019CBio...29E3953S. doi: 10.1016/j.cub.2019.09.050 . ISSN   0960-9822. PMID   31679935. S2CID   204972040.
  13. ↑ Schlebusch, Carina M.; Jakobsson, Mattias (2018-08-31). "Tales of Human Migration, Admixture, and Selection in Africa". Annual Review of Genomics and Human Genetics. 19 (1): 405–428. doi: 10.1146/annurev-genom-083117-021759 . ISSN   1527-8204. PMID   29727585.
  14. ↑ Lazaridis, Iosif; Nadel, Dani; Rollefson, Gary; Merrett, Deborah C.; Rohland, Nadin; Mallick, Swapan; Fernandes, Daniel; Novak, Mario; Gamarra, Beatriz; Sirak, Kendra; Connell, Sarah; Stewardson, Kristin; Harney, Eadaoin; Fu, Qiaomei; Gonzalez-Fortes, Gloria (2016-08-25). "Genomic insights into the origin of farming in the ancient Near East". Nature. 536 (7617): 419–424. Bibcode:2016Natur.536..419L. doi:10.1038/nature19310. ISSN   0028-0836. PMC   5003663 . PMID   27459054.
  15. ↑ Vicente, Mário; Schlebusch, Carina M (2020-06-01). "African population history: an ancient DNA perspective". Current Opinion in Genetics & Development. Genetics of Human Origin. 62: 8–15. doi: 10.1016/j.gde.2020.05.008 . ISSN   0959-437X. PMID   32563853. S2CID   219974966.
  16. ↑ Hammarén, Rickard; Goldstein, Steven T.; Schlebusch, Carina M. (2022-08-28). "Eurasian back-migrations into Northeast Africa was a complex and multifaceted process": 2022.08.27.505526. doi:10.1101/2022.08.27.505526. S2CID   251956429.{{cite journal}}: Cite journal requires |journal= (help)
  17. ↑ Hammarén, Rickard; Goldstein, Steven T.; Schlebusch, Carina M. (2023-11-08). "Eurasian back-migration into Northeast Africa was a complex and multifaceted process". PLOS ONE. 18 (11): e0290423. Bibcode:2023PLoSO..1890423H. doi: 10.1371/journal.pone.0290423 . ISSN   1932-6203. PMC   10631636 . PMID   37939042.
  18. ↑ Callaway, Ewen (2015-10-08). "First ancient African genome reveals vast Eurasian migration". Nature. doi:10.1038/nature.2015.18531. ISSN   1476-4687. S2CID   181867810.
  19. ↑ Llorente, M. Gallego; Jones, E. R.; Eriksson, A.; Siska, V.; Arthur, K. W.; Arthur, J. W.; Curtis, M. C.; Stock, J. T.; Coltorti, M. (2015-11-13). "Ancient Ethiopian genome reveals extensive Eurasian admixture in Eastern Africa". Science. 350 (6262): 820–822. doi: 10.1126/science.aad2879 . hdl: 2318/1661894 . ISSN   0036-8075. PMID   26449472.
  20. ↑ Haber, Marc; Mezzavilla, Massimo; Bergström, Anders; Prado-Martinez, Javier; Hallast, Pille; Saif-Ali, Riyadh; Al-Habori, Molham; Dedoussis, George; Zeggini, Eleftheria; Blue-Smith, Jason; Wells, R. Spencer; Xue, Yali; Zalloua, Pierre A.; Tyler-Smith, Chris (2016-12-01). "Chad Genetic Diversity Reveals an African History Marked by Multiple Holocene Eurasian Migrations". American Journal of Human Genetics. 99 (6): 1316–1324. doi:10.1016/j.ajhg.2016.10.012. ISSN   0002-9297. PMC   5142112 . PMID   27889059.
  21. ↑ Chen, Lu; Wolf, Aaron B.; Fu, Wenqing; Li, Liming; Akey, Joshua M. (2020-02-20). "Identifying and Interpreting Apparent Neanderthal Ancestry in African Individuals". Cell. 180 (4): 677–687.e16. doi:10.1016/j.cell.2020.01.012. ISSN   1097-4172. PMID   32004458.
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