Genetic Heterogeneitybetween Berbers andArabsLara R Arauna, Institut de Biologia Evolutiva (CSIC-UPF), Departament de CiènciesExperimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain

David Comas, Institut de Biologia Evolutiva (CSIC-UPF), Departament de CiènciesExperimentals i de la Salut, Universitat Pompeu Fabra, Barcelona, Spain

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Article Contents• Introduction

• Genetic Diversity in Berber and Arab Groups

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Online posting date: 15th September 2017

The human population history of North Africahas been different from the rest of the conti-nent, and it has been characterised by populationreplacements, extensive continuous gene flow,and differential admixture from neighbouringregions. This complex demographic landscape hasyielded a large degree of genetic heterogeneityamong North African populations. Recent histori-cal admixture processes have been inferred fromgenome-wide data; no correlation between genet-ics and ethnic groups has been described, pointingto a lack of genetic differentiation between Berberand Arab groups in North Africa. This complexgenetic population structure should be taken intoaccount when designing biomedical approaches inNorth African groups.

Introduction

Little is known about the initial human settlement in NorthAfrica, the movements during the Upper Paleolithic (known asthe ‘Late Stone Age’ in the study of African prehistory) andthe possible introgression from archaic humans, such as Nean-derthals (Green et al., 2010) and Denisovans (Reich et al., 2010)or other unknown African hominins (Hammer et al., 2011), tothe populations inhabiting this area. Recent description of formsof Homo sapiens with a mosaic of modern and primitive char-acteristics in North Africa dated back to ∼300 000 ya (yearsago) has even challenged the geographical origins of our species(Hublin et al., 2017). However, the first presence of anatomi-cally modern humans (AMHs) in North Africa has been estimated190 000–130 000 ya by archaeological studies (much older thanprevious estimates that dated the first occupation of the region

eLS subject area: Evolution and Diversity of Life

How to cite:Arauna, Lara R and Comas, David (September 2017) GeneticHeterogeneity between Berbers and Arabs. In: eLS. John Wiley& Sons, Ltd: Chichester.DOI: 10.1002/9780470015902.a0027485

∼45 000 ya) (Smith et al., 2007). The Aterian is the first prehis-toric industry characterised in North Africa (Barton et al., 2009),which has been suggested to have started around 120 000 ya.Although paradoxical, the Sahara desert has been reported to bea corridor for the movement of people during the ‘green Sahara’periods thanks to its watercourses. The old dates of AMH remainsand the Sahara corridor leave many open questions about the roleof North Africa in the origin of modern humans and their disper-sal out of the continent. Different hypotheses have been proposed:Was North Africa just a stop on the road out of Africa, or did itplay a more important role in the evolution of modern humans?

No clear connections have been established between this firsthuman industry and subsequent cultures in the region, such as theIberomaurusian industry (22 000–9500 ya) (Newman, 1995). Theprefix ‘Ibero-’ refers to the ancient presumption that this cultureextended into Iberia, although an origin in the Nile River valley iswidely accepted (Camps, 1995). The Iberomaurusian culture wasfollowed by the Capsian industry (10 000–4700 ya) (Newman,1995) that persisted well into the Neolithic, which began around5500 ya in the region. The prehistoric cultural changes in NorthAfrica were independent of the change dynamics on the Europeanshores of the Mediterranean.

Based on archaeology and linguistics, it has been arguedthat the peopling of North Africa has not been continuous andthat population replacements may have occurred in differentmoments. Genetic data (Henn et al., 2012) has supported thispopulation replacement hypothesis in North Africa, suggesting aback-to-Africa migration from the Middle East in pre-Holocenetimes, older than 12 000 ya. The ancestors of today’s NorthAfrican populations derive at least partially from this migrationwave; however, it is not clear if this replacement was completeor there might be some traces of ancient continuity in the region.Therefore, many open questions remain about the demography ofthe region in relation to the demographic continuity of humanssince the first occupation of North Africa by modern humans,such as how many times a population replacement took place andwhich are the demographic parameters such as population size ofthe migrants and where did they come from.

The challenges of the understanding of North African pop-ulations are not limited to prehistoric times: in historic times,North Africa has also experienced a very complex history that isreflected in its human demography. Historical records documenttrade routes across the Sahara and contacts between both Mediter-ranean shores and the Middle East. Phoenicians (814 B.C.) and

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Genetic Heterogeneity between Berbers and Arabs

Romans (146 B.C.) occupied part of coastal North Africa withlimited population contributions, which were even less signifi-cant for Vandals (A.D. 429) and Byzantines (A.D. 533) (New-man, 1995). One of the major historical events in the regionthat changed the cultural and demographic landscape of NorthAfrica is the Arabisation. The first Arab invasion, initially con-fined to Egypt, started in A.D. 643 and may have involved only afew thousand individuals (McEvedy, 1995). The Arabs began toimpose their religion and language over the Berber autochthonouspopulation, a process that culminated with a second and largerArab wave in which the Bedouin reached the Maghreb (northwestAfrica) in the eleventh century. The Islamic expansion even wenton to engulf the Iberian Peninsula (A.D. 711). The later arrivalsto North Africa in colonial times include Europeans and OttomanTurks, mainly in Egypt.

Nowadays in North Africa, two main groups of languages arespoken: Berber and Arab dialects. Both belong to the Afroasiaticfamily, which is a group of languages that might have originatedin the Mesolithic, between 15 000 and 10 000 ya. Although it isnot clear, one of the most plausible places of origin of Afroasiaticlanguages is the ‘grassland east of the Nile Valley’ (Newman,1995). However, it is unknown if the arrival of the Afroasiaticlanguages was mainly a cultural diffusion process or it alsoimplied a relevant demographic movement.

The Berbers (Amazighen, as they call themselves) are con-sidered the autochthonous people of North Africa. As can beelucidated from the complex and unsolved prehistory and his-tory of North Africa, it is difficult to establish an origin for theBerbers, and many hypotheses have been proposed. Historicalrecords reveal their presence before the Phoenician arrival tothe region (Camps, 1998), and archaeologically, it has been sug-gested a link between the Capsian culture and the Berber people(Camps, 1995). However, the Berbers might not have been a uni-form and homogeneous group, since it has been known that thepopulations that inhabited North Africa by the time of the Phoeni-cian arrival were a composite group known as Libyco-Berbers,where we find the Garamantes, Bavares, Mauri, Gaetuli, amongmany others (Newman, 1995). In addition to the uncertaintiesabout the origins of the Berbers, the arrival of other people inthe region, especially the influence of Arabs, makes the under-standing of the population history of Berbers more challenging.

Considering these previous points, the population genetics def-inition of today’s Berber and Arab groups is a complex task.Different points of view can be considered to determine whethera population is considered as Berber or not. Berbers can be under-stood as non-Semitic autochthonous populations in North Africa,although it is challenging to determine which current populationsderive from an ancestral autochthonous group in North Africa.Another way to identify Berbers and Arabs is regarding their cul-tural characteristics, but again, the cultural exchange in recenthistory of North Africa has been common, and it is difficult todifferentiate, for example, an Arabised Berber society from anArab population in North Africa, among many other combina-tions. Given this combination of circumstances, the best optionfor a classification may be based on linguistics, Berber popula-tions being those who speak Berber languages and Arabs beingthose speaking Arab (Dugoujon et al., 2009). This classifica-tion could be the way of having less ‘false positives’; however,

this classification is not free of caveats, and populations identi-fied as Arabs or non-Berbers could in fact have a large Berbergenetic ancestry. It is important to emphasise that the purpose ofthis classification is to understand the genetics of North Africanpopulations and in any case to establish socio-cultural groups,which should take into consideration many other aspects (tradi-tions, identity, etc.).

Despite the scanty genetic data on North African groups, pop-ulation genetics might shed some light on the genetic structure ofBerbers and Arabs, trying to establish the demographic scenariosthat have modelled the current genetic landscape in North Africa.

Genetic Diversity in Berber andArab Groups

The human genetic data of North Africa is scarce compared toother regions of the African continent, and most of the Africangenetic diversity studies have been focused on the origin of ourspecies and the first dispersions out of Africa (see, for instance,Tishkoff et al., 2009), the genetic diversity of North Africanpopulations and surrounding groups being poorly characterised.

The analyses based on frequencies of classical genetic poly-morphisms (blood groups, red cell enzymes and serum proteins)have shown that the genetic landscape in North Africa presents aneast-west pattern of variation without differences between Arabsand Berbers, pointing to a sizeable Upper Paleolithic componentin current North African populations, whereas the Neolithic dif-fusion in the region was more a cultural than a demic process(Barbujani et al., 1994; Bosch et al., 1997). These classical stud-ies showed little contribution from sub-Saharan populations inNorth Africans and genetic differentiation from southern Euro-peans, including Iberians (Bosch et al., 1997). However, the anal-ysis of mtDNA lineages has shown an important sub-Saharancontribution, although most haplogroups in North Africa are ofwest-Eurasian origin (Fadhlaoui-Zid et al., 2004, 2011b; Kringset al., 1999; Plaza et al., 2003; Rando et al., 1998). Some ofthem can be traced to ancient Paleolithic times (such as hap-logroups U6, M1, which are almost specific of North Africanpopulations); however, some maternal lineages have been theresult of a more recent acquisition from Europe or the Mid-dle East (such as haplogroups U5, V, R0a, J1b, U3) (Gonzálezet al., 2007; Maca-Meyer et al., 2003; Olivieri et al., 2006)(Figure 1). In addition, a large degree of genetic heterogene-ity has been shown in North African maternal and paternal lin-eages compared to other geographical regions such as Europe(Fadhlaoui-Zid et al., 2004, 2011a; Plaza et al., 2003). The anal-ysis of Y-chromosome lineages has shown a high frequency oftwo specific North African haplogroups (E-M81 and E-M78)(Figure 1), although their origins have been controversial sincesome analyses have suggested a Paleolithic component (Boschet al., 2001), whereas others have pointed to a Neolithic ori-gin (Arredi et al., 2004; Cruciani et al., 2004, 2007; Seminoet al., 2004). The data on autosomal markers in North Africanpopulations based on some short tandem repeats (STRs) (Boschet al., 2000) and Alu polymorphisms (Comas et al., 2000; Flo-res et al., 2000; González-Pérez et al., 2010) has been analysed

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Genetic Heterogeneity between Berbers and Arabs

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Figure 1 Haplogroup frequencies for different Berber and Arab populations for (a) mitochondrial DNA (data from Coudray et al., 2009 and Plaza et al.,2003) and (b) Y chromosome (data from Arredi et al., 2004).

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Genetic Heterogeneity between Berbers and Arabs

in few North African samples pointing to a closer genetic affin-ity to West Eurasian populations. Y-chromosome lineages andautosomal markers show a clear differentiation of North Africanpopulations with some sub-Saharan gene flow and almost negli-gible European contact (Bosch et al., 2000, 2001; Comas et al.,2000; González-Pérez et al., 2010). Nonetheless, the contributionof North African female and male lineages in the Iberian Penin-sula (Adams et al., 2008; Plaza et al., 2003) should be stressed.

Genome-wide analyses have recently become the most pow-erful tool to unravel the genetic history of populations. The firstlarge genome-wide study in North Africa analysing several NorthAfrican and surrounding populations (Henn et al., 2012) sug-gested the existence of an autochthonous North African compo-nent whose origin is located out of Africa before the Holocene(>12 000 years ago) and a complex admixture from the Mid-dle East, Europe and sub-Saharan Africa. This autochthonousNorth African component was found in high frequencies in theonly Berber sample (Berber Tunisian from Chenini) analysed inthe study, suggesting that Berbers might be responsible for thisautochthonous component in North African samples. However,recent genome-wide data with additional Berber samples haveshown a different scenario, with some Berber groups present-ing less frequencies of the autochthonous component comparedto some Arab groups (Arauna et al., 2017). In addition to theautochthonous component in North Africa, it has been possible toquantify and estimate the recent dates of the sub-Saharan admix-ture in North Africa (Henn et al., 2012) as well as the geneticcontacts from North Africa mainly restricted to south-westernEurope (Botigué et al., 2013). Concerning the introgression ofarchaic hominins into North Africans, some Neanderthal admix-ture is detected in these groups independent of their Europeancomponent (Sánchez-Quinto et al., 2012).

Most of the genetic studies in North African populations agreewith a limited or non-existent correlation between genetics andgeography, and therefore, they show a high population hetero-geneity in the region (Bosch et al., 2000; Fadhlaoui-Zid et al.,2004; Flores et al., 2011; González-Pérez et al., 2010). How-ever, an east-west genetic pattern of variation has been observed(Arauna et al., 2017; Bosch et al., 1997; Harich et al., 2001; Hennet al., 2012), which has been explained by Middle Eastern geneflow towards North Africa according to genome-wide analyses(Arauna et al., 2017; Henn et al., 2012). The genetic heterogene-ity is not only due to the wide extension of North Africa, since itis also found at microgeographical level when considering morerestricted areas, such as Algeria (Bekada et al., 2015) or Tunisia(Fadhlaoui-Zid et al., 2011a; Kefi et al., 2015), for instance.Regardless of the genetic markers analysed, North African popu-lations have been described as a mosaic of North African, MiddleEastern, European and sub-Saharan ancestries. The differentialadmixture with these four ancestry sources explains the currentgenetic structure in North Africa, characterised by diverse andheterogeneous populations. This differential admixture explainswhy nearby populations or even individuals inhabiting the samelocation might be genetically more distant than groups of peo-ple in geographically distant populations. For instance, NorthAfrican individuals with similar amounts of sub-Saharan admix-ture present high genetic similarities regardless of their geograph-ical origin. Neither geography, linguistics nor ethnic affiliation

is correlated with a specific pattern of admixture proportions. Acompletely different scenario was shown when analysing NorthAfrican Jews, who are genetically closer to other Jewish popula-tions than to their geographic neighbours (Campbell et al., 2012).There are many possible scenarios that might explain the dif-ferential admixture in North Africa, socio-cultural structure andhistorical events being the main reasons. However, more com-plex socio-cultural scenarios, including socio-economic factors,a more precise ethnic or linguistic definition, particularities ofthe history of each local area and rural versus urban lifestyles,should be considered in order to find a correlation with the com-plex genetic pattern observed (Arauna et al., 2017).

Concerning the genetic differences between Berber and Arabgroups, classical and uniparental markers have highlighted thelack of a genetic structure that could differentiate Berber andArab populations (Bekada et al., 2015; Fadhlaoui-Zid et al., 2004;Harich et al., 2001; Kefi et al., 2015). Most of these authors haveagreed on a cultural rather than a demographic impact of theArabisation after the Arab expansion (Bosch et al., 2000, 2001;Ennafaa et al., 2011; Flores et al., 2011). However, as stated ear-lier, an East-to-West genetic gradient of a Middle Eastern compo-nent has been described in genome-wide analyses, and admixtureevents have been dated to the Arabisation period (Arauna et al.,2017; Henn et al., 2012), suggesting that the Arabisation mighthave had more demographic impact than previously thought.The first widespread genome-wide study in North Africa (Hennet al., 2012) suggested that the single Berber sample analysed(Tunisian Berber from Chenini) presented high frequencies of anautochthonous North African component (named in the study the‘Maghrebi’ component) and negligible presence of the MiddleEastern component. This lack of Middle Eastern component inBerbers and its higher frequencies in Arabs pointed to a genomedifferentiation between both North African groups. However, theposterior genome-wide analysis of additional Berber samples haschallenged this genetic differentiation idea (Arauna et al., 2017).This study has corroborated the lack of genetic differentiationbetween Berbers and Arabs; however, it has shown that the Arabi-sation had also a demographic impact in North Africa (Figure 2).It is difficult to exactly quantify the magnitude of the Arab geneticcontribution during the Arab expansion in the seventh century,among other reasons because the influence from Middle East hasbeen continuous into North Africa (Camps, 1995). Therefore, thisdata supports the lack of significant differences between Berberand Arabs, but points to a new explanation: a high and differentiallevel of admixture since the Arab expansion that has affected mostNorth African groups regardless of their Berber or Arab identity.

The other genetic components that are present in North Africanpopulations also contribute to the heterogeneity between Berberand Arabs. Both peoples have admixed with sub-Saharan popula-tions in the last two millennia regardless of their ethnicity, whichhas contributed to the lack of differentiation between both groups(Flores et al., 2000; Harich et al., 2010; Henn et al., 2012). How-ever, it has been shown that the sub-Saharan admixture is mostfrequent in the southern groups, and in fact, a South-North gradi-ent of sub-Saharan admixture has been described in North Africa(Comas et al., 2000; Plaza et al., 2003), which sometimes canmimic differences between Arab and Berber populations that are

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Genetic Heterogeneity between Berbers and Arabs

Morocco S. Morocco N. Sahara Algeria

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Figure 2 Analyses of autosomal markers. Each bar shows the proportion of the genome that each individual share with each of the four ancestral populationsaccording to ChromoPainter analyses (Lawson et al., 2012). The separation between bars within each population represents clusters of individuals with similarancestry proportions. Source: Arauna et al. (2017).

mainly explained by a differential sub-Saharan contribution (Flo-res et al., 2011).

The high heterogeneity found in North African populationsis also present within ethnic groups. Berbers are a compositeof groups with very different demographic characteristics, andsome Berber groups are genetic outliers compared to other Berberor North African populations. This is the case of the TunisianBerber population from Chenini, which has been analysed foruniparental and genome-wide markers, and in both cases, it hasbeen described as an outlier group compared to their NorthAfrican populations (Ennafaa et al., 2011; Fadhlaoui-Zid et al.,2004, 2011a; Henn et al., 2012). This genetic singularity isnot exclusive of this group since other Tunisian Berber groupshave also shown similar outlier characteristics (Ennafaa et al.,2011; Fadhlaoui-Zid et al., 2004, 2011a). Another example arethe Mozabite, an Algerian Berber group included in the HumanGenome Diversity Panel (HGDP) (Cann et al., 2002), whichhave been extensively analysed in many genetic studies and havealso been described as an outlier group within North Africa andalso within Berbers (Bekada et al., 2015; Plaza et al., 2003).It is important to note that Mozabite have been considered asthe representative North African group in a large number ofstudies due to the fact that they are the only North Africangroup in the HGDP, which should be taken with caution giventheir genetic outlier characteristics. Furthermore, the Siwa Berberpopulation from Egypt is genetically distant from other Berbergroups from West North Africa (Coudray et al., 2009), suggestinga differentiation between Egyptian Berbers and Western Berbers.However, there are many other Berber groups that are closelyrelated between them and to other North African groups. All theseevidences support a high diversity within Berbers, which couldbe explained by isolation processes and inbreeding. For example,the Chenini population is an isolated population that shows highlevels of inbreeding (Arauna et al., 2017; Henn et al., 2012). It hasbeen described that some of the diversity observed within Berbersis due to the belonging to an urban or rural area. Rural areas favourisolation leading to genetic differentiated populations (Brakezet al., 2001; Ennafaa et al., 2011; Frigi et al., 2006). On theother hand, urban areas that are less isolated are more favourableto high admixture levels and lead to the lack of differentiationbetween Berber and Arab groups. Finally, it is important to

notice the wide extension and fragmentation of the territory wherethe Berbers live, which could lead to population differentiationbecause of many reasons apart from ethnicity (simply by isolationby distance or differential gene flow). Then, it is important tocompare the Berber groups to geographically close populationsin order to make inferences of genetic distances.

The genetic heterogeneity of North African samples, the com-plex population admixture patterns and the lack of correla-tion between genetics and ethnic groups should be taken intoaccount when addressing biomedical approaches in North Africa.Ignoring these population aspects might lead to artefacts andfalse-positive results when searching for associations betweengenetic markers and biomedical phenotypes, including diseaseassociation studies. Furthermore, population genetic studies inNorth Africa should also take this diversity into account. It isimportant to trace many different variables when studying NorthAfrican populations, such as the social and demographic char-acteristics of the studied groups (if it is urban or rural, if it isgeographically isolated, etc.) and their history (the Arab influencein the region, slave trade routes, etc.). The genetic structure ofNorth African population is determined by many different factorsapart from a simple ethnic dichotomy Arab–Berber, and includingthose variables sheds lights in the understanding of the popula-tions.

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Reconstructing Human History Using Autosomal, Y-Chro-mosomal and Mitochondrial MarkersGene Flow, Haplotype Patterns and Modern Human OriginsGenetic Diversity in AfricaHumans: Demographic History

Glossary

Admixture The process of mixing of different populationswithin a species.

Cultural diffusion The spread of cultural practices fromanother group of people without genetic exchange.

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Genetic Heterogeneity between Berbers and Arabs

Demic diffusion The spread of a population in an advancingwave.

Gene flow The movement of genetic variation from onepopulation to another.

Haplogroup A group of similar allele combinations that share acommon ancestor.

Inbreeding Reproduction that involves genetically relatedindividuals.

Introgression The process of mixing of different species.

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Further Reading

Camps G (1974) Les civilisations préhistoriques de l’Afrique duNord et du Sahara.

Hublin J-J and McPherron PS (eds) (2012) Modern Origins. A NorthAfrican Perspective. New York: Springer.

Nielsen R, Akey JM, Jakobsson M, et al. (2017) Tracing the peoplingof the world through genomics. Nature 541 (7637): 302–310.

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