May 08, 2013

The Geography of Recent Genetic Ancestry across Europe (Ralph and Coop 2013)

This paper first came out last July on the arXiv and went through four versions there before its final form which has now appeared in PLoS Biology. It's great that its early release allowed other people to read it without having to wait for the completion of the peer review process.

I think that this is a good model: journals have the right and obligation to subject papers to close scrutiny according to their own procedures, but this process ought not interfere with the early availability of research results or the ability of anyone other than the chosen reviewers to comment on new results.

PLoS Biol 11(5): e1001555. doi:10.1371/journal.pbio.1001555

The Geography of Recent Genetic Ancestry across Europe

Peter Ralph, Graham Coop

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.

Link

3 comments:

Dr Rob said...

This is a great paper. As I personally let the authors know last year, I found it interesting that, on the one had, SouthEast Europeans are more diverse than any other European groups (from a Y DNA Hg perspective; ie harbouring R1b, R1a, E-V13, I2, J2, all variuosly at levels > 10%), are "older" than northern and western Europeans (eg look at heterozygostiy and LD from autosomal data); yet on the other hand also share clear evidence of more recent genetic affinities which the WE's lack

It is as if Western Europe was settled later than SEE (no surprise) but then the populations there remained somewhat more parochial viz-aviz each other.

eurologist said...

Nice paper.

Our results are therefore one of the first genomic demonstrations of the counterintuitive but necessary fact that all Europeans are genealogically related over very short time periods, and lends substantial support to models predicting close and ubiquitous common ancestry of all modern humans.

This deserves being emphasized.

Also, interesting to see how stark the signature of very recent Slavic expansion/ population replacement is.

Average Joe said...

Our results are therefore one of the first genomic demonstrations of the counterintuitive but necessary fact that all Europeans are genealogically related over very short time periods, and lends substantial support to models predicting close and ubiquitous common ancestry of all modern humans.

But not all humans are equally closely related. People from the same ethnic group tend to be more closely related to each other than they are to people from different ethnic groups.