A geografia da recente ancestralidade genética por toda a Europa
segunda-feira, maio 27, 2013
The Geography of Recent Genetic Ancestry across Europe
Peter Ralph, Graham Coop
Abstract
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.
Author Summary
Few of us know our family histories more than a few generations back. It
is therefore easy to overlook the fact that we are all distant cousins,
related to one another via a vast network of relationships. Here we use
genome-wide data from European individuals to investigate these
relationships over the past 3,000 years, by looking for long stretches
of genome that are shared between pairs of individuals through their
inheritance from common genetic ancestors. We quantify this ubiquitous
recent common ancestry, showing for instance that even pairs of
individuals from opposite ends of Europe share hundreds of genetic
common ancestors over this time period. Despite this degree of
commonality, there are also striking regional differences. Southeastern
Europeans, for example, share large numbers of common ancestors that
date roughly to the era of the Slavic and Hunnic expansions around 1,500
years ago, while most common ancestors that Italians share with other
populations lived longer than 2,500 years ago. The study of long
stretches of shared genetic material promises to uncover rich
information about many aspects of recent population history.
Citation: Ralph P, Coop G (2013) The Geography of Recent Genetic
Ancestry across Europe. PLoS Biol 11(5): e1001555.
doi:10.1371/journal.pbio.1001555
Academic Editor: Chris Tyler-Smith, The Wellcome Trust Sanger Institute, United Kingdom
Received: July 16, 2012; Accepted: March 27, 2013; Published: May 7, 2013
Copyright: © 2013 Ralph, Coop. This is an open-access article
distributed under the terms of the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any
medium, provided the original author and source are credited.
Funding: GC: Sloan Foundation Fellowship, www.sloan.org. PR: Ruth L.
Kirschstein Fellowship, NIH #F32GM096686, grants.nih.gov. The funders
had no role in study design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: IBD, identity by descent; SNP, single nucleotide polymorphism; ya, years ago
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