The Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape

Abstract

SummaryOver 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 humans across West Eurasia, demonstrating the presence of large-scale, dynamic population movements over the last 10,000 years, such that ancestry across present-day populations is likely to be a mixture of several ancient groups [1, 2, 3, 4, 5, 6, 7]. While 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 [8, 9, 10, 11]. Here, using recently described haplotype-based techniques [11], 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 1200 CE. Comparisons of the genetic profiles of West Eurasians before and after admixture show that population movements within the last 1,500 years are likely to have maintained differentiation among groups. Our analysis provides a timeline of the gene flow events that have generated the contemporary genetic landscape of West Eurasia.

Complex Ancient Genetic Structure and Cultural Transitions in Southern African Populations

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Complex interplay between neutral and adaptive evolution shaped differential genomic background and disease susceptibility along the Italian peninsula

“…Nevertheless, the absence of a Yamnaya-related genetic signature in the northern Italian Copper Age Remedello specimen suggests that these migrations could have reached the Italian peninsula considerably later34. Moreover, roughly overlapping migrations occurred during the expansion of the Roman Empire or in Medieval times could have also reinforced and/or re-shaped this pattern1213, with the former events being the most plausible responsible for the signature observed in N_ITA according to time estimates obtained by ALDER analysis (Supplementary Table S2). Finally, the light blue component was observed in eastern and northern European populations, being predominant in Finn plausibly due to high genetic drift, but reached equal and negligible frequencies in Italian groups (2.8%).…”

Ancient and recent admixture layers in Sicily and Southern Italy trace multiple migration routes along the Mediterranean

“…While ancient DNA (aDNA) based studies have been providing new insights into the early European heritage 2–8 , high-resolution genomic analyses focused on modern-day populations allow to explore more recent genomic layers and historical demographic events 9–15 .…”