September 19, 2015

Recent admixture in contemporary West Eurasians

After applying Globetrotter to the world and to the British, a new study in Current Biology applies to the intermediately-sized region of West Eurasia. This is an open-access article, so go ahead and read it.

Current Biology DOI:

The Role of Recent Admixture in Forming the Contemporary West Eurasian Genomic Landscape
George B.J. Busby et al.

Over 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 [ 1–7 ]. 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 [ 8–11 ]. 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.



Simon_W said...

Figure 4C is fascinating. It should resolve many nationalist and local patriot quarrels about whose people were more influential, at least as far as biological influence and the not too distant past is concerned. A few observations:

You can clearly see the Slavic expansion, which surprisingly looks bimodal, with a Lithuanian-like western center and an Ukrainian-like eastern center.

You can also see the Germanic expansion to the British Isles, and Benelux, and more surprisingly, Finland, but not into the Slavic populations.

The French-like expansion to Italy, Germany and Spain is dated to the Middle Ages, and may be related to the heydays of the Frankish empire.

The date of the Norwegian migration to Northern Britain fits the Viking age. I'm a bit surprised the arrow doesn't go anywhere else. In contrast, there is also a fat arrow going from Britain to Norway, that's unexpected!

Another fat British arrow goes into France, and, interestingly, into Basques. That's probably the explanation for the elevated frequency of R1b-L21 in Basques! The date is Medieval, around 1000 AD +/- 250 years. And from 1000 BC to the common era Basques show no admixture at all. (Which possibly matters in the question of R1b-L51 origins.)

Italy shows an interesting emigration pattern, with the North going to Sardinia, Spain and France, and somewhat less to Southern Italy, whereas the South goes to Anatolia, somewhat less to Hungary, and in thin arrows also to Germany, British Isles and France. I guess these migrations already started during the Roman era, but apparently were continued later.

Greece goes only to Southern Italy and Sicily, the dates suggest the Byzantine era.

Northern Italy and Tuscany are affected by Cypriot-like immigrants, the date seems mostly like Roman and Byzantine era. This certainly must have contributed to the spread of the West Asian autosomal component and yDNA haplogroup J2a in these regions.

Very surprising is the extremely wide and considerably strong spread of Bulgarian-like influence into all directions. This even reached Northern Britain, the Caucasus and central Asia! What the heck was this?

Also surprising the slight Turkish-like admixture into Poland, Ukraine and Belorussia, dated to about 800 – 1100 AD. What might this be?

Simon_W said...

Correction: the blue Northwest European arrow into Basques is from Germany, not Britain.

Simon_W said...

I've always believed Englishmen hardly ever left their island for the continent, they emigrated to the new world and other overseas colonies. Now this data shows something quite different.

Aram said...

Thank You Dienekes for the link.

Simon_W said...

I've changed my mind; an admixture edge of >50% from England to Norway in the common era is simply not believable. I think a much more plausible explanation would be that a British-like element was already at home in Norway, and then got admixed with some minor eastern gene-flow to produce modern Norwegians. Hence it would look as if Britons came and brought along more than 50% of the gene-pool, but that's an outlandish interpretation.

Also, a high mixing coefficient with the English in the French and the Tuscans was already detected by Hellenthal et al. Together with other coefficients they interpreted these as Welsh-like admixture in the French and French-like admixture in Tuscans. So again, a simple, real English admixture in these populations probably isn't the correct interpretation of the data.

Gary Moore said...

The high degree of exchange between the British and Norwegians should be of no surprise, in view of the Scandinavian incursions into the British Isles. The Norman victory at Hastings lead to a diaspora of the old Anglo-Saxon aristocracy. Many served with the Byzantine Varangian Guard and formed a significant component of the "Frankish" mercenaries employed by Muslim rulers in the Middle East. Medieval Britons were active in the Baltic trade and also fought in large numbers in the Iberian wars. The Normans also conquered and ruled Sicily and parts of southern Italy.

One disappointment, in view of the suspected Native American generic affinity of the Huns, is that the researchers did not look for a Native American component.

Martin Lewitt said...

Is it unreasonable to think that British women were among the plunder taken back to Norway? With their men defeated and scattered, history may not have recorded their plight.