Synthesizing genetic and genealogical data to trace historical waves of European and African immigration to the United States. J. K. Byrnes1, J. M. Granka1, K. Noto1, R. E. Curtis2, Y. Wang1, M. J. Barber1, N. M. Myres2, C. A. Ball1, K. G. Chahine2 1) Ancestry.com DNA L.L.C., 153 Townsend St., Ste. 800, San Francisco, CA; 2) Ancestry.com DNA L.L.C., 360 West 4800 North, Provo, UT.

   Census data can reveal waves of immigration, with immigrants from a single source population migrating to roughly the same U.S. locations within a short period of time. A refinement of the timings and locations of migratory waves using genetic and genealogical data would be useful not only for understanding the peopling of the U.S., but also for understanding patterns of genetic disease risk. To examine migratory waves using genealogical and genetic data, we first identify IBD-enriched groups: groups of U.S. AncestryDNA customers who share elevated amounts of DNA identity-by-descent (IBD) with a reference panel of individuals with known deep ancestry from a single location. Elevated IBD with individuals from one location could indicate a source population from which ancestors of a customer originated. As a proof of principle, for individuals in a group that is IBD-enriched for a particular location, we search for an enrichment of ancestors born in this location across the collection of their pedigrees. Then, for each IBD-enriched group, we search the collection of pedigrees for enrichment of more recent birth locations, representing migratory destinations within the U.S. Among over 100,000 U.S. AncestryDNA customer samples, we identify IBD-enriched groups who have elevated IBD with more than 20 European countries and seven West African population groups. For each IBD-enriched group, we present maps showing patterns of ancestor birth location enrichment through time. As expected, customers in an IBD-enriched group to a particular location have an enrichment of ancestor births in that location, though this enrichment is dependent on pedigree completeness (e.g. it is rare for African Americans to have known ancestors from West Africa in their pedigrees). For some punctuated migratory waves, such as the arrival of Norwegian immigrants in the Midwest during the 19th century, clear signals of both source and migratory destinations are visible. These locations are temporally ordered, with ancestors from the migratory destination appearing more recently in the pedigrees than ancestors from the source location. Finally, we are able to pinpoint the age and origin of particular haplotypes defining IBD-enriched groups. With our approach, we demonstrate that we can estimate individual ancestral origins and detail human migratory history by jointly studying estimates of genetic relatedness along with genealogical data.

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