ben hamed - can genetics help unravel the afroasiatic cradle
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7/27/2019 Ben Hamed - Can Genetics Help Unravel the Afroasiatic Cradle
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Can Genetics help unravel the Afroasiatic cradle?MahE9 BEN HAMED1,2, LounE8s CHIKHI3 and Pierre DARLU2
1 Laboratoire Dynamique du Langage, UMR5596, Lyon, France2 GE9nE9tique EpidE9miologique et Structure des populations humaines,
U535, Villejuif, France3 UMR Evolution et DiversitE9 Biologique, Toulouse, France
The location of the Afroasiatic cradle and the routes ofexpansion of this linguistic family have long been debated. Twoscenarios compete. The first scenario (Militarev et al., 1992) connectsthe history of this linguistic family with the expansion of the majorEurasian linguistic phyla which are themselves thought to have beenbrought during the agriculturalist revolution in the Near-East about10-13,000 years ago. This scenario is supported by the Russianlinguistic school and the Nostratic tenants who consider the Afroasiaticis related to the Nostratic macro-family. .On the contrary, afrasianhistorical linguists support a second scenario where the Afro-Asiatic isthought to have originated in eastern Lower Nubia and to be at least15,000 years old (Ehret, 1979, 1995). It has been difficult to clearlydemonstrate the superiority of any of the two scenarios as tenants from
both sides have sometimes used the same methodologies to reach oppositeconclusions. Moreover, some of the methodologies used such as linguisticpalaeontology and glottochronology are often criticised among thelinguistic community. One possible explanation for obtaining suchparadoxical conclusions is that there might be methodologicaldeficiencies in the way the issue is handled (Ben Hamed and Darlu,2003). The debate is thus left wide open, and it remains as topical nowas it was when Afro-Asiatic was first established as a linguisticphylum, at the beginning of the 20th Century (Cohen, 1924).
Given the existing controversy among linguists and the scarcityof archaeological data to solve the Afroasiatic homeland puzzle (McCall,1998), it is legitimate to ask whether genetic data could be as useful
as it has been on similar issues on other linguistic groups. In aresearch context favouring multidisciplinary approaches, reconciling thethree approaches would certainly be a significant improvement. .Currently, the Anatolian scenario is probably the most appealing for itis both synthetic and parsimonious. It provides a powerful explanationfor the expansion of this and other linguistic families. Indeed, a demicdiffusion scenario starting in the same region is becoming increasinglysupported in the case of Indo-European and some of the other Nostraticbranches. If confirmed this would identify the Fertile Crescent as thecradle of the neighbouring linguistic diversity, and the demic diffusionmodel as a paradigm for the study of populations92 evolution in theseregions at least.
In the present talk we will take an indirect approach to theproblem, which cannot on its own answer the whole cradle issue, butwhich can test the consistency of the genetic data with specificlinguistic scenarios. Both scenarios imply migratory events.Correlatively, in the demic model of a linguistic family expansion,admixture patterns between the migrating people and the local demes areexpected. Provided appropriate parental hypotheses 96 i.e. whichpopulation represents the migratory wave, and which will represent thesubstratum submitted to admixture- it is possible to infer admixturepatterns from the observed genetic frequencies of present-day
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populations. We confront here different admixture methods relying ondifferent assumptions in order to embrace all the evolutionary forcesthat can shape the admixture profile of the populations under study(Chikhi et al., 2001; Bertorelle and Excoffier, 1998; Wijsman, 1984).The profiles thus obtained are confronted with each of the scenariosproposed for Afro-asiatic.
Bibliography:
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Chikhi L, Bruford MW, Beaumont MA., Estimation of admixture proportions:a likelihood-based approach using Markov chain Monte Carlo. Genetics,2001 Jul; 158(3):1347-62.
Cohen M., Les langues chamito-sE9mitiques, in Meillet A., Cohen M.(eds), Les Langues du monde, Paris. (1924)
Ehret C., On the antiquity of agriculture in Ethiopia, Journal ofAfrican History, 1979, 20: 161-117.
Ehret C., Reconstructing Proto-Afroasiatic (Proto-Afrasian): Vowels,Tone, Consonants, and Vocabulary, University of California Publicationsin Linguistics 126, University of California Press, Berkeley and LosAngeles (1995).
Mc Call D.F., The Afroasiatic Language Phylum: African in Origin, orAsian? Current Anthropology, 1998, Vol.39 no.1 pp.139-143.20
Militarev A., Shnirelman V., The Problem of a Proto-Afrasian homelandand culture (An essay in linguo-archaeological reconstruction), A
Journal of Composition Theory, 1992, 7: 121-130.
Wijsman E.M., Techniques for estimating genetic admixture andapplications to the problem of the origin of the Icelanders and theAshkenazi Jews. Hum Genet. 1984; 67(4):441-8.