2-AIN-505, 2-AIN-251: Seminar in Bioinformatics (1), (3)
Winter 2023

Peter Ralph, Graham Coop. The geography of recent genetic ancestry across Europe. PLoS biology, 11(5):e1001555. 2013.

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The recent genealogical history of human populations is a complex mosaic formed 
by individual migration, large-scale population movements, and other demographic 
events. Population genomics datasets can provide a window into this recent 
history, as rare traces of recent shared genetic ancestry are detectable due to 
long segments of shared genomic material. We make use of genomic data for 2,257 
Europeans (in the Population Reference Sample [POPRES] dataset) to conduct one of 
the first surveys of recent genealogical ancestry over the past 3,000 years at a 
continental scale. We detected 1.9 million shared long genomic segments, and used 
the lengths of these to infer the distribution of shared ancestors across time 
and geography. We find that a pair of modern Europeans living in neighboring 
populations share around 2-12 genetic common ancestors from the last 1,500 years, 
and upwards of 100 genetic ancestors from the previous 1,000 years. These numbers 
drop off exponentially with geographic distance, but since these genetic 
ancestors are a tiny fraction of common genealogical ancestors, individuals from 
opposite ends of Europe are still expected to share millions of common 
genealogical ancestors over the last 1,000 years. There is also substantial 
regional variation in the number of shared genetic ancestors. For example, there 
are especially high numbers of common ancestors shared between many eastern 
populations that date roughly to the migration period (which includes the Slavic 
and Hunnic expansions into that region). Some of the lowest levels of common 
ancestry are seen in the Italian and Iberian peninsulas, which may indicate 
different effects of historical population expansions in these areas and/or more 
stably structured populations. Population genomic datasets have considerable 
power to uncover recent demographic history, and will allow a much fuller picture 
of the close genealogical kinship of individuals across the world.