Genetic history of North Africa
The genetic history of North Africa has been heavily influenced by geography. The Sahara desert to the south and the Mediterranean Sea to the North were important barriers to gene flow in prehistoric times. However, Northeast Africa and the Levant form a single land mass at the Suez. At the Straits of Gibraltar, North Africa and Europe are separated by only 15 km (9 mi). At periods of low sea-levels, such as during a glacial maximum, islands that are currently submerged would appear in the Mediterranean and possibly in between the Gibraltar straits.
These may have encouraged humans to "island hop" between Africa and Europe. During wetter phases of the Sahara, some Saharan inhabitants would have expanded north into southern parts of North Africa. West Asian populations would have also been attracted to a wet Sahara. West Asian populations could also migrate into Africa via the coastal regions of the Mediterranean.
As a result of these geographic influences, the genetic profile of North African populations is a complex mosaic of European, West Asian and Sub-Saharan African influences to variable degrees. Though North Africa has experienced gene-flow from the surrounding regions, it has also experienced long periods of genetic isolation in some parts, allowing a distinctive genetic markers to evolve in some Maghrebi populations, especially in some isolated Berber speaking people.
Current scientific debate is concerned with determining the relative contributions of different periods of gene flow to the current gene pool of North Africans. Anatomically modern humans are known to have been present in North Africa during the Upper Paleolithic, 45,000 years ago, as attested by the Aterian culture. With no apparent continuity, 22,000 years ago, the Aterian was succeeded by the Iberomaurusian industry, whose lithic assemblages bore relations with the Cro-Magnon cultures. The Iberomaurusian was succeeded by the Capsian, a pre-Neolithic culture. Around 9,000 years ago, the Sahara desert entered a wet phase, the Neolithic Subpluvial, which attracted Neolithic peoples from elsewhere in Africa and the Near East.
In historic times, North Africa was occupied by various populations, including the Phoenicians (814–146 BCE), Romans (146 BCE–439 CE), Vandals and Alains (439–534 CE), and Byzantines (534–647 CE). In the 7th century, Islam was diffused in the area. Under the unifying framework of Islam, on the one hand, and the settlement of some Middle Eastern tribes together with the migration of the Moors of Andalusia into the Maghreb (after the Spanish Catholic Reconquista) on the other, a fusion took place that resulted in a new ethnocultural entity all over the Maghreb and Egypt and all contributed to the diffusion of the Arab-Islamic culture among the North African populations.
Haplogroup E is the most prevalent haplogroup amongst the Berbers accounting for up to 87 percent of Y-chromosomes among some Berber populations. Haplogroup E is thought to have emerged in East Africa, and would have later dispersed into North Africa and West Asia. The major subclades of haplogroup E found amongst Berbers belong to E1b1b1, which is believed to have emerged in North Africa. Common subclades include E1b1b1a, E1b1b1b and E1b1b1*. E1b1b1b is distributed along a west-to-east cline with frequencies that can reach as high as 80 percent in Northwest Africa. E1b1b1a has been observed at low to moderate frequencies among Berber populations with significantly higher frequencies observed in Northeast Africa relative to Northwest Africa.
West Eurasian haplogroups, such as Haplogroup J and Haplogroup R1, have also been observed at moderate frequencies. A thorough study by Arredi et al. (2004), which analyzed populations from Algeria, concludes that the North African pattern of Y-chromosomal variation (including both J1 and E3b2 main haplogroups) is largely of Neolithic origin, which suggests that the Neolithic transition in this part of the world was accompanied by demic diffusion of Berber–speaking pastoralists from the Middle East 
E1b1b1b (E-M81); formerly E3b1b, E3b2
E1b1b1b (E-M81) is the most common Y chromosome haplogroup in North Africa, dominated by its sub-clade E-M183. It is thought to have originated in North Africa 5,600 years ago. The parent clade, E1b1b, originated in East Africa. Colloquially referred to as the Berber marker or Maghrebi marker for its prevalence among Mozabite, Middle Atlas, and other berber speaker groups, E-M81 is also quite common among North African groups. It reaches frequencies of up to 80 percent in some parts of the Maghreb. This includes the Saharawish for whose men Bosch et al. (2001) reports that approximately 76 percent are M81+.
This haplogroup is also found in small amounts in the Iberian Peninsula, Italy, France, Sardinia and Canary islands. In Iberia, it is generally more common than E1b1b1a (E-M78), unlike the rest of Europe, and as a result E-M81 is found throughout Latin America and among Hispanic men in USA. As an exceptional case in Europe, this sub-clade of E1b1b1 has also been observed at 40 percent the Pasiegos from Cantabria.
Another theory by Gonçalves suggests that, since the percentage of E in Iberia is high in areas with little to no Moorish/Berber settlement, such as Galicia, Castile and Cantabria, the lineage may have been brought to Iberia by Neolithic or Mesolithic migrations. The cause for such migrations may have been the drying out of the Sahara and the movement of populations from Northwest Africa across the Strait of Gibraltar northward to more temperate Iberia. This theory suggests a pre-Islamic prehistoric migration from North Africa into Iberia that has left behind a genetic trace in the modern Iberian population. More research is required in determining how close the subclades of E carried by Iberian men are related to Maghrebis, and whether they are exactly the same subclade. This would help to determine whether E-M81's presence in Iberia is prehistoric or from more recent periods, such the Islamic civilization of Al-Andalus.
There are two recognized sub-clades, although one is much more common than the other.
- Sub clades of E1b1b1b (E-M81):
Individuals receive mtDNA only from their mothers. According to Macaulay et al. 1999, "one-third of Mozabite Berber mtDNAs have a Near Eastern ancestry, probably having arrived in North Africa less than 50,000 years ago, and one-eighth have an origin in sub-Saharan Africa. Europe appears to be the source of many of the remaining sequences, with the rest having arisen either in Europe or in the Near East". Maca-Meyer et al. 2003 analyze the "autochthonous North African lineage U6" in mtDNA, and conclude that:
- The most probable origin of the proto-U6 lineage was the Near East. Around 30,000 years ago it spread to North Africa where it represents a signature of regional continuity. Subgroup U6a reflects the first African expansion from the Maghreb returning to the east in Paleolithic times. Derivative clade U6a1 signals a posterior movement from East Africa back to the Maghreb and the Near East. This migration coincides with the probable Afroasiatic linguistic expansion.
A genetic study by Fadhlaoui-Zid et al. 2004 argues concerning certain exclusively North African haplotypes that "expansion of this group of lineages took place around 10,500 years ago in North Africa, and spread to neighbouring population", and apparently that a specific Northwestern African haplotype, U6, probably originated in the Near East 30,000 years ago accounts for 28 percent in Mozabites, 18 percent in Kabyles, but has not been preserved in the southern Moroccan Berbers and accounts for 6-8 percent. Rando et al. 1998 (as cited by ) "detected female-mediated gene flow from sub-Saharan Africa to NW Africa" amounting to as much as 21.5 percent of the mtDNA sequences in a sample of NW African populations; the amount varied from 82 percent in Tuaregs (inhabitants of south part of the sahara and in contact for centuries with the sub-saharan population) to less than 3 percent in Riffians in north of Morocco. This north-south gradient in the sub-Saharan contribution to the gene pool is supported by Esteban et al.
Nevertheless, individual Berber communities display a considerably high mtDNA heterogeneity among them. The Berbers of Jerba Island, located in South Eastern Tunisia, display an 87 percent West Eurasian contribution with no U6 haplotypes, while the Kesra of Tunisia, for example, display a much higher proportion of typical sub-Saharan mtDNA haplotypes (49 percent), as compared to the Zriba (8 percent). According to the article, "The North African patchy mtDNA landscape has no parallel in other regions of the world and increasing the number of sampled populations has not been accompanied by any substantial increase in our understanding of its phylogeography. Available data up to now rely on sampling small, scattered populations, although they are carefully characterized in terms of their ethnic, linguistic, and historical backgrounds. It is therefore doubtful that this picture truly represents the complex historical demography of the region rather than being just the result of the type of samplings performed so far."
Haplotype V, have its highest concentration among the Saami people of northern Scandinavia (approximately 59%). It has been found at approximately 10% among the Maris of the Volga-Ural region, leading to the suggestion that this region might be the source of the V among the Saami.
Haplogroup V is also found at higher than average levels in Cantabrian people (15%) of northern Iberia, and somewhat lower in nearby Basque people (10.4%). It also is found in particularly high concentrations (16.3%) among the Berbers of Matmata, Tunisia. The frequency of haplotype V is to be observed throughout the Mediterranean region, ranging from frequencies of close to 30 percent in southern Portugal to around 10 percent in southern France. Similarly, the highest frequency in Italy is to be found in the southern island of Sicily (28 percent).
Additionally, recent studies have discovered a close mitochondrial link between Berbers and the Saami of Scandinavia, which confirms that Southwestern Europe was the source of late-glacial expansions of hunter-gatherers that repopulated Northern Europe after the Last Glacial Maximum and reveals a direct maternal link between those European hunter-gatherer populations and the Berbers. With regard to Mozabite Berbers, one-third of Mozabite Berber mtDNAs have a Near Eastern ancestry, probably having arrived in North Africa ∼50,000 years ago, and one-eighth have an origin in sub-Saharan Africa. Europe appears to be the source of many of the remaining sequences, with the rest having arisen either in Europe or in the Near East."
According to the most recent and thorough study on Berber mtDNA from Coudray et al. 2008, which analysed 614 individuals from 10 different regions (Morocco (Asni, Bouhria, Figuig, Souss), Algeria (Mozabites), Tunisia (Chenini-Douiret, Sened, Matmata, Jerba) and Egypt (Siwa)), the results may be summarized as follows:
- Total West Eurasian lineages (H, HV, R0, J, T, U (without U6), K, N1, N2, X) : 50-80 percent
- Total sub-Saharan lineages (L0, L1, L2, L3, L4, L5) : 20-40 percent
- Total North African lineages (U6, M1) : 10-30 percent
The Berber mitochondrial pool is characterized by an overall high frequency of Western Eurasian haplogroups, a somehow lower frequency of sub-Saharan L lineages, and a significant (but differential) presence of North African haplogroups U6 and M1.
Until recently, some papers suggested that the distribution of the main L haplogroups in North Africa was mainly due to trans-Saharan slave trade. However, in September 2010, a thorough study of Berber mtDNA by Frigi et al. concluded that most of L haplogroups were much older and introduced by an ancient African gene flow around 20,000 years ago.
On 13 January 2012, an exhaustive genetic study of North Africa's human populations was published in PLoS Genetics and was undertaken jointly by researchers in the Evolutionary Biology Institute (CSIC-UPF) and Stanford University, among other institutions.
The study reveals that the genetic composition of North Africa's human populations is extremely complex, and the result of a local component dating back thirteen thousand years and the varied genetic influence of neighbouring populations on North African groups during successive migrations. According to David Comas, coordinator of the study and researcher at the Institute for Evolutionary Biology (CSIC-UPF), "some of the questions we wanted to answer were whether today's inhabitants are direct descendants of the populations with the oldest archaeological remains in the region, dating back fifty thousand years, or whether they are descendants of the Neolithic populations in the Middle East, which introduced agriculture to the region around eight thousand years ago. We also wondered if there had been any genetic exchange between the North African populations and the neighbouring regions and if so, when these took place".
To answer these questions, the researchers analyzed around 800,000 genetic markers, distributed throughout the entire genome in 125 North African individuals belonging to seven representative populations in the whole region, and the information obtained was compared with the information from the neighbouring populations.
The results of this study show that there is a native genetic component that defines North Africans. In-depth study of these markers shows that the people inhabiting North Africa today are not descendants of either the earliest occupants of this region fifty thousand years ago, or of the most recent Neolithic populations.
The data shows that the ancestors of today's North Africans were a group of populations that already lived in the region around thirteen thousand years ago. Furthermore, this local North African genetic component is very different from the one found in the populations in the south of the Sahara, which shows that the ancestors of today's North Africans were members of a subgroup of humanity who left Africa to conquer the rest of the world and who subsequently returned to the north of the continent to settle in the region.
As well as this local component, North African populations were also observed to share genetic markers with all the neighbouring regions, as a result of more recent migrations, although these appear in different proportions.
There is an influence from the Middle East, which becomes less marked as the distance from the Arabian Peninsula increases, similar proportions of European influence in all North African populations, and, in some populations, there are even individuals who present a large proportion of influence from the South of the Sahara in their genome.
A 2015 study by Dobon et al. identified an ancestral autosomal component of West Eurasian origin that is common to many modern Afro-Asiatic-speaking populations in Northeast Africa. Known as the Coptic component, it peaks among Egyptian Copts who settled in Sudan over the past two centuries. The Coptic component evolved out of a main North African and Middle Eastern ancestral component that is shared by other Egyptians and also found at high frequencies among other Afro-Asiatic populations in Northeast Africa (~70%). The scientists suggest that this points to a common origin for the general population of Egypt. They also associate the Coptic component with Ancient Egyptian ancestry, without the later Arabian influence that is present among other Egyptians.
The general parent Y-chromosome Haplogroup E1b1b (formerly known as E3b), which might have originated in the Horn of Africa or the Near East is by far the most common clade in North and Northeast Africa and found in select populations in Europe, particularly in the Mediterranean and South Eastern Europe. E1b1b reaches in Europe Greece and the Balkan region but, is not as high there as it is among African populations..
Outside of North and Northeast Africa, E1b1b's two most prevalent clades are E1b1b1a (E-M78, formerly E3b1a) and E1b1b1b (E-M81, formerly E3b1b).
E1b1b1a is the most common subclade of E1b1b and is present predominantly in Northeast Africa. It was originally thought to have been a marker of Neolithic migrations (perhaps coinciding with the introduction of Agriculture into Europe) from Anatolia to Europe, via the Balkans, where it enjoys the high frequency. However, Cruciani's latest study suggests that it actually arrived into the Balkans from Western Asia during the Palaeolithic, and then spread throughout Europe much later (c. 5300 years ago) due to a population expansion from Egypt. E1b1a is also found at low frequencies in this area.
A study from Semino (published 2004) showed that Y-chromosome haplotype E1b1b1b (E-M81), is specific to North African populations and almost absent in Europe except the Iberia (Spain and Portugal) and Sicily. Another 2004 study showed that E1b1b1b is found present, albeit at low levels throughout Southern Europe (ranging from 1.5 percent in Northern Italians, 2.2 percent in Central Italians, 1.6 percent in Southern Spaniards, 3.5 percent in the French, 4 percent in the Northern Portuguese, 12.2 percent in the Southern Portuguese and 41.2 percent in the genetic isolate of the Pasiegos from Cantabria).
The findings of this latter study contradict a more thorough analysis Y-chromosome analysis of the Iberian peninsula according to which haplogroup E1b1b1b surpasses frequencies of 10 percent in Southern Spain. The study points only to a very limited influence from Northern Africa and the Middle East in Iberia, both in historic and prehistoric times. The absence of microsatellite variation suggests a very recent arrival from North Africa consistent with historical exchanges across the Mediterranean during the period of Islamic expansion, namely of Berber populations. However, a study restricted to Portugal, concerning Y-chromosome lineages, revealed that "The mtDNA and Y-DNA data indicate that the presence of Berbers in that region dates clearly prior to the Moorish expansion in 711 AD, so it´s not recent there at all. ... Our data indicate that male Berbers, unlike sub-Saharan immigrants, constituted long-lasting and continuous community in the country".
A wide-ranging study (published 2007) using 6,501 unrelated Y-chromosome samples from 81 populations found that: "Considering both these E-M78 sub-haplogroups (E-V12, E-V22, E-V65) and the E-M81 haplogroup, the contribution of northern African lineages to the entire male gene pool of Iberia (barring Pasiegos), continental Italy and Sicily can be estimated as 5.6 percent, 3.6 percent and 6.6 percent, respectively." It has also been argued that the European distribution of E-M78 and its sub-clades is compatible with the Neolithic demic diffusion of agriculture, but also possibly partly from at least, the Mesolithic. For example, Battaglia et al. (2007) estimated that E-M78 (called E1b1b1a1 in that paper) has been in Europe longer than 10,000 years. In support of this theory, human remains excavated in a Spanish funeral cave dating from approximately 7,000 years ago were shown to be in this haplogroup. More recently, two E-M78 have been found in the Neolitich Sopot and Lengyel cultures from the same period.
High-resolution analysis of human Y-chromosome variation shows a sharp discontinuity and limited gene flow between northwestern Africa and the Iberian Peninsula (Bosch E, Calafell F, Comas D, Oefner PJ, Underhill PA, Bertranpetit J.) which seems supported by the most recent studies (including autosomal research).
A very recent study about Sicily by Gaetano et al. 2008 found that "The Hg E3b1b-M81, widely diffused in northwestern African populations, is estimated to contribute to the Sicilian gene pool at a rate of 6 percent." .
According to the most recent and thorough study about Iberia by Adams et al. 2008 that analysed 1,140 unrelated Y-chromosome samples in Iberia, a limited contribution of northern African lineages to the entire male gene pool of Iberia was found : "mean North African admixture is just 10.6 percent, with wide geographical variation, ranging from zero in Gascony to 21.7 percent in Northwest Castile". More recent extensive/complete studies, like «The Geography of Recent Genetic Ancestry across Europe», determined that Italians and Iberians, in fact, share very few common ancestors with other populations over at least, the last 2.500 years, unlike all the other European populations, present on the study, so North African contribution in both peninsulas is very likely limited (always a minority even in «hotspot» areas), many times constituted by ancient haplogroups, and in many cases, geographically not compatible with Moor invasion.
Genetic studies on Iberian populations also show that North African mitochondrial DNA sequences (haplogroup U6) and sub-Saharan sequences (Haplogroup L), although present at only low levels, are still at higher levels than those generally observed elsewhere in Europe, though very likely, most of the L mtDNA that has been found in minor amounts in Iberia, is actually pre-neolithic in origin, as it was demonstrated by María Cerezo et al., (Reconstructing ancient mitochondrial DNA links between Africa and Europe) and U6 too, which also have a very old presence in Iberia, since Iberia has a great diversity in lineages from this haplogroup, it was already found in some local hunter-gatherer remains and its local geographic distribution is not compatible, in many cases, with Moor occupation area. Haplogroup U6 have also been detected in Sicily and Southern Italy at much lower frequencies. It happens also to be a characteristic genetic marker of the Saami populations of Northern Scandinavia.
It is difficult to ascertain that U6's presence is the consequence of Islam's expansion into Europe during the Middle Ages, particularly because it is more frequent in the west of the Iberian Peninsula rather than in the east. In smaller numbers it is also attested in the British Isles, again in its northern and western borders. It may be a trace of a prehistoric Neolithic/Megalithic/Mesolithic or even Upper Paleolithic expansion along the Atlantic coasts from North Africa or Iberian Peninsula, perhaps in conjunction with seaborne trade, although an alternative, but less likely explanation, would attribute this distribution in Northern Britain to the Roman period. One subclade of U6 is particularly common among Canarian Spaniards as a result of native Guanche (proto-Berber) ancestry.
Genetic influences on Latin America
In 2013, Nature announced the publication of the first genetic study utilizing next-generation sequencing to ascertain the ancestral lineage of an Ancient Egyptian individual. The research was led by Carsten Pusch of the University of Tübingen in Germany and Rabab Khairat, who released their findings in the Journal of Applied Genetics. DNA was extracted from the heads of five Egyptian mummies that were housed at the institution. All the specimens were dated to between 806 BC and 124 AD, a timeframe corresponding with the Late Dynastic and Ptolemaic periods. The researchers observed that one of the mummified individuals likely belonged to the mtDNA haplogroup I2, a maternal clade that is believed to have originated in Western Asia.
In 2013, Iberomaurusian skeletons from the prehistoric sites of Taforalt and Afalou in the Maghreb were analyzed for ancient DNA. All of the specimens belonged to maternal clades associated with either North Africa or the northern and southern Mediterranean littoral, indicating gene flow between these areas since the Epipaleolithic. The ancient Taforalt individuals carried the mtDNA haplogroups U6, H, JT and V, which points to population continuity in the region dating from the Iberomaurusian period.
- Y-DNA haplogroups by populations of Near East and North Africa
- Population history of Egypt
- Archaeogenetics of the Near East
- Ethnic groups of North Africa
- African admixture in Europe
- Genetic studies on Jews
- Genetic studies on Arabs
- Genetic history of the Iberian Peninsula
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- See for example Flores et al. (2004).
- See the remarks of genetic genealogist Robert Tarín for example. We can add 6.1 percent (8 out of 132) in Cuba, Mendizabal et al. (2008); 5.4 percent (6 out of 112) in Brazil (Rio de Janeiro), "The presence of chromosomes of North African origin (E3b1b-M81; Cruciani et al., 2004) can also be explained by a Portuguese-mediated influx, since this haplogroup reaches a frequency of 5.6 percent in Portugal (Beleza et al., 2006), quite similar to the frequency found in Rio de Janeiro (5.4 percent) among European contributors.", Silva et al. (2006)
- 2.4 percent (7 out of 295) among Hispanic men from California and Hawaii, Paracchini et al. (2003)
- Y-DNA Haplogroup E and its Subclades - 2008
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- Di Gaetano, C.; Cerutti, N.; Crobu, F.; Robino, C.; Inturri, S.; Gino, S.; Guarrera, S.; Underhill, P. A.; King, R. J.; et al. (2008). "Differential Greek and northern African migrations to Sicily are supported by genetic evidence from the Y chromosome". European Journal of Human Genetics 17 (1): 91–99. doi:10.1038/ejhg.2008.120. PMC 2985948. PMID 18685561. "The co-occurrence of the Berber E3b1b-M81 (2.12 percent) and of the Mid-Eastern J1-M267 (3.81 percent) Hgs together with the presence of E3b1a1-V12, E3b1a3-V22, E3b1a4-V65 (5.5 percent) support the hypothesis of intrusion of North African genes. (...) These Hgs are common in Northern Africa and are observed only in Mediterranean Europe and together the presence of the E3b1b-M81 highlights the genetic relationships between northern Africa and Sicily. (...) Hg E3b1b-M81 network cluster confirms the genetic affinity between Sicily and North Africa."
- Adams, S. M.; Bosch, E.; Balaresque, P. L.; Ballereau, S. P. J.; Lee, A. C.; Arroyo, E.; López-Parra, A. M.; Aler, M.; Grifo, M. S. G. (2008). "The Genetic Legacy of Religious Diversity and Intolerance: Paternal Lineages of Christians, Jews, and Muslims in the Iberian Peninsula". The American Journal of Human Genetics 83 (6): 725–736. doi:10.1016/j.ajhg.2008.11.007. PMC 2668061. PMID 19061982.
- "The study shows that religious conversions and the subsequent marriages between people of different lineage had in fact a minor impact on modern populations both in Spain, and in Portugal", The religious conversions of Jews and Muslims have had an impact on the population of the Iberian Peninsula, Elena Bosch, 2008
- Plaza, S.; Calafell, F.; Helal, A.; Bouzerna, N.; Lefranc, G.; Bertranpetit, J.; Comas, D. (2003). "Joining the Pillars of Hercules: MtDNA Sequences Show Multidirectional Gene Flow in the Western Mediterranean". Annals of Human Genetics 67 (4): 312–28. doi:10.1046/j.1469-1809.2003.00039.x. PMID 12914566. But very likely, most of the L mtDNA that has been found in minor amounts in Iberia, is actually pre-neolithic in origin, as it was demonstrated by María Cerezo et al., (Reconstructing ancient mitochondrial DNA links between Africa and Europe). "Haplogroup U6 is present at frequencies ranging from 0-7 percent in the various Iberian populations, with an average of 1.8 percent. Given that the frequency of U6 in NW Africa is 10 percent, the mtDNA contribution of NW Africa to Iberia can be estimated at 18 percent (though U6 has been found in many Iberian hunter-gatherer remains as well). This is larger than the contribution estimated with Y-chromosomal lineages (7 percent) (Bosch et al. 2001).
- Pereira, L.; Cunha, C.; Alves, C.; Amorim, A. (2005). "African Female Heritage in Iberia: A Reassessment of mtDNA Lineage Distribution in Present Times". Human Biology 77 (2): 213–229. doi:10.1353/hub.2005.0041. PMID 16201138. "Although the absolute value of observed U6 frequency in Iberia is low, it reveals a discernible North African female contribution, if we keep in mind that haplogroup U6 is not very common in North Africa itself and virtually absent in the rest of Europe. Indeed, because the range of variation in western North Africa is 4-28 percent, the estimated minimum input is 8.54 percent"
- GonzáLez, A. M.; Brehm, A.; Pérez, J. A.; Maca-Meyer, N.; Flores, C.; Cabrera, V. M. (2003). "Mitochondrial DNA affinities at the Atlantic fringe of Europe". American Journal of Physical Anthropology 120 (4): 391–404. doi:10.1002/ajpa.10168. PMID 12627534. "Our results clearly reinforce, extend, and clarify the preliminary clues of an 'important very ancient mtDNA contribution from northwest Africa into the Iberian Peninsula' (Côrte-Real et al., 1996; Rando et al., 1998; Flores et al., 2000a; Rocha et al., 1999)(...) Our own data allow us to make minimal estimates of the maternal African pre-Neolithic, Neolithic, and/or recent slave trade input into Iberia. For the former, we consider only the mean value of the U6 frequency in Northern African populations, excluding Saharans, Tuareg, and Mauritanians (16 percent), as the pre-Neolithic frequency in that area, and the present frequency in the whole Iberian Peninsula (2.3 percent) as the result of the northwest African gene flow at that time. The value obtained (14 percent) could be as high as 35 percent using the data of Corte-Real et al. (1996), or 27 percent with our north Portugal sample."
- Achilli, A.; Olivieri, A.; Pala, M.; Metspalu, E.; Fornarino, S.; Battaglia, V.; Accetturo, M.; Kutuev, I.; Khusnutdinova, E. (2007). "Mitochondrial DNA Variation of Modern Tuscans Supports the Near Eastern Origin of Etruscans". The American Journal of Human Genetics 80 (4): 759–68. doi:10.1086/512822. PMC 1852723. PMID 17357081. "1.33% (3/226) in Calabria and 1.28 percent in Campania"
- See the remarks of genetic genealogist Robert Tarín for example. We can add 6.1 percent (eight out of 132) in Cuba
- Mendizabal, I.; Sandoval, K.; Berniell-Lee, G.; Calafell, F.; Salas, A.; Martinez-Fuentes, A.; Comas, D. (2008). "Genetic origin, admixture, and asymmetry in maternal and paternal human lineages in Cuba". BMC Evolutionary Biology 8: 213. doi:10.1186/1471-2148-8-213. PMC 2492877. PMID 18644108. "The presence of chromosomes of North African origin (E3b1b-M81; Cruciani et al., 2004) can also be explained by a Portuguese-mediated influx, since this haplogroup reaches a frequency of 5.6 percent in Portugal (Beleza et al., 2006), quite similar to the frequency found in Rio de Janeiro (5.4 percent) among European contributors"
- Silva, D. A.; Carvalho, E.; Costa, G.; Tavares, L. G.; Amorim, A. N.; Gusmão, L. (2006). "Y-chromosome genetic variation in Rio De Janeiro population". American Journal of Human Biology 18 (6): 829–837. doi:10.1002/ajhb.20567. PMID 17039481.
- Coco, C.; Magistrelli, P.; Granone, P.; Roncolini, G.; Picciocchi, A. (1992). "Conservative surgery for early cancer of the distal rectum". Diseases of the Colon & Rectum 35 (2): 131. doi:10.1007/BF02050667.
- Rabab Khairat, Markus Ball, Chun-Chi Hsieh Chang, Raffaella Bianucci, Andreas G. Nerlich, Martin Trautmann, Somaia Ismail; et al. (4 April 2013). "First insights into the metagenome of Egyptian mummies using next-generation sequencing" (PDF). Journal of Applied Genetics. doi:10.1007/s13353-013-0145-1. Retrieved 8 June 2016.
- Kefi R, Bouzaid E, Stevanovitch A, Beraud-Colomb E. "MITOCHONDRIAL DNA AND PHYLOGENETIC ANALYSIS OF PREHISTORIC NORTH AFRICAN POPULATIONS" (PDF). ISABS. Retrieved 17 January 2016.
- Bernard Secher, Rosa Fregel, José M Larruga, Vicente M Cabrera, Phillip Endicott, José J Pestano and Ana M González. "The history of the North African mitochondrial DNA haplogroup U6 gene flow into the African, Eurasian and American continents". BMC Evolutionary Biology. Retrieved 8 February 2016.