Out of Africa, which way? L. Pagani1,2,3, T. Kivisild2, S. Shiffels1, A. Scally4, Y. Chen1, Y. Xue1, P. Danecek1, J. Maslen1, M. Haber5, R. Ekong6, T. Oljira7, E. Mekonnen7, D. Luiselli3, E. Bekele7, P. Zalloua5, C. Tyler-Smith1 1) The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, United Kingdom; 2) Division of Biological Anthropology, University of Cambridge, CB2 1QH, UK; 3) Department of Biological, Geological and Environmental Sciences of the University of Bologna; Italy; 4) Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK; 5) The Lebanese American University, Chouran, Beirut, Lebanon; 6) Department of Genetics, Evolution & Environment, University College London, WC1E 6BT, UK; 7) University of Addis Ababa, and Center of Human Genetic Diversity, P.O. Box 1176, Ethiopia.
While the African origin of all modern human populations is well-established, the dynamics of the diaspora that led anatomically modern humans to colonize the lands outside Africa are still under debate. Understanding the demographic parameters as well as the route (or routes) followed by the ancestors of all non-Africans could help to refine our understanding of the selection processes that occurred subsequently, as well as shedding light on a landmark process in our evolutionary history. Of the three possible gateways out of Africa (via Morocco across the Gibraltar strait, via Egypt through the Suez isthmus or via the Horn of Africa across Bab el Mandeb strait) only the latter two are supported by paleoclimatic and archaeological evidence. Furthermore, recent studies (Pagani et al. 2012) showed that, although the modern Ethiopian populations might be good candidates for the descendants of the source population of such a migration, modern Egyptians could be an even better candidate. Unfortunately, however, only a few Egyptian samples have been genotyped and, as yet, none have been fully sequenced. Here, we have generated 125 Ethiopian and 100 Egyptian whole genome sequences (Illumina HiSeq, 8x average depth). The genomes were partitioned using PCAdmix (Brisbin et al. 2012) to account for the confounding effects of recent introgression from neighboring non-African populations. To explore the genetic legacy of migration routes out of Africa, and in particular to test whether the observed genetic data support one route over another, the African components of Egyptians and Ethiopians were then compared to a panel of available non-African populations from the 1000 Genomes Project (1000 Genomes Project Consortium, 2012). The high resolution provided by whole genome sequencing allows us to shed new light on the paths followed by our ancestors as they left Africa, as well as refining the current knowledge of the demographic history of the populations analyzed.
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