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[QUOTE]Originally posted by zarahan- aka Enrique Cardova: [QB] [QUOTE]Originally posted by Doug M: [qb] A recent study entitled The Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape has been published pointing out multiple waves of admixture in Western Europe: [QUOTE] We investigated the effect of admixture—the process of mixing of haplotypes between genetically differentiated ancestral groups—in each of these clusters using GLOBETROTTER. First, we painted each recipient individual’s chromosomes such that they were represented as mosaics of chunks of different ancestry from a set of donor groups that included all 18 World Regions together with other clusters from within West Eurasia. We then used summaries of the amount of genome-wide donor ancestry from these mosaics, together with information on the lengths and distributions of specific ancestral chunks, to infer whether admixture is likely to have occurred in a recipient group and to characterize the composition and proportion that each donor group contributed to the sources of the admixture event. ... The vast majority of clusters (78%; 64 out of 82) showed evidence of admixture, suggesting that admixture-facilitated gene flow is a fundamental property of almost all West Eurasian groups (Tables S4 and S5; Supplemental Information). Here, we discuss the broader patterns of ancestry across West Eurasia, with a more detailed assessment of admixture events provided in the Supplemental Information. Throughout, we refer to the inferred groups characterized by GLOBETROTTER as contributing to an admixture event as 'sources' and the sampled groups contributing ancestry to these sources as “donors.” It is also important to note that in the discussion presented below, we use current-day geographic labels to describe ancestry of historical sources of admixture. When we describe the ancestry of a particular source as, for example, 'Mongolian,' this is a convenient but less precise proxy for 'ancestry in a historical group that is related to the ancestry that we observe in contemporary Mongolian populations today.' This shorthand aids reading, but one must bear in mind that while the inferred sources of admixture are likely to be closely related genetically to the true historical admixing groups, because of subsequent population movements and migration, they may be less closely related geographically to the original source of that ancestry. [/QUOTE] http://dx.doi.org/10.1016/j.cub.2015.08.007 [/qb][/QUOTE]ABSTRACT Over the past few years, studies of DNA isolated from human fossils and archaeological remains have generated considerable novel insight into the history of our species. Several landmark papers have described the genomes of ancient human ancestors and have demonstrated that contemporary humans harbour genetic material from ancient close relatives, the Neanderthals and Denisovans, and that ancient human individuals are often genetically distinct from nearby extant populations whilst also showing affinities with populations from further afield. Across West Eurasia, there is growing genetic evidence of large-scale, dynamic population movements over the period between 10,000 to 2,000 years ago, such that the ancestry across present-day populations is likely to be a mixture of several ancient groups. Whilst these efforts are bringing the details of West Eurasian prehistory into increasing focus, studies aimed at understanding the processes behind the generation of the current West Eurasian genetic landscape have been limited by the number of populations sampled, or have been either too regional or global in their outlook. Here, using recently described haplotype-based techniques, we present the results of a systematic survey of recent admixture history across Western Eurasia and show that admixture is a universal property across almost all groups. Admixture in all regions except North Western Europe involved the influx of genetic material from outside of West Eurasia, which we date to specific time periods. Within Northern, Western, and Central Europe, admixture tended to occur between local groups during the period 300 to 1200CE. Comparisons of the genetic profiles of West Eurasians before and after admixture show that population movements within the last 1500 years are likely to have maintained differentiation amongst groups. Our analysis provides a timeline of the gene flow events that have generated the contemporary genetic landscape of West Eurasia. -- Busby et al 2015. Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape. Current Bio. 2015 [/QB][/QUOTE]
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