Genetic History of the Balkans

Romans on the Danube, from Trajan's column

New paper by Olalde et al., "Cosmopolitanism at the Roman Danubian Frontier, Slavic Migrations, and the Genomic Formation of Modern Balkan Peoples." Abstract: 

The Roman Empire expanded through the Mediterranean shores and brought human mobility and cosmopolitanism across this inland sea to an unprecedented scale. However, if this was also common at the Empire frontiers remains undetermined. The Balkans and Danube River were of strategic importance for the Romans acting as an East-West connection and as a defense line against “barbarian” tribes. We generated genome-wide data from 70 ancient individuals from present-day Serbia dated to the first millennium CE; including Viminacium, capital of Moesia Superior province. Our analyses reveal large scale-movements from Anatolia during Imperial rule, similar to the pattern observed in Rome, and cases of individual mobility from as far as East Africa. Between ∼250-500 CE, we detect gene-flow from Central/Northern Europe harboring admixtures of Iron Age steppe groups. Tenth-century CE individuals harbored North-Eastern European-related ancestry likely associated to Slavic-speakers, which contributed >20% of the ancestry of today’s Balkan people. 

So they find three major population changes in the Classical and Medieval Balkans:

1. The arrival of people from eastern Mediterranean, who moved across the late Republic and early Empire by the hundreds of thousands, either as slaves or in search of opportunity.
2. Invaders who carried genes from the West Asian/East European steppes arriving between 250 and 500 AD; these are presumably Goths, Vandals, Gepids, Heruli, and sundry other barbarians.
3. Slavs, arriving between 500 and 900 AD, who contribute 20 percent of the genes of modern Balkan peoples.

If you were thinking of asking where the Slavs came from, well, 

The Slavs, who raided the Balkans during the 6th century and settled in the region in the 7th century, had a particularly long-lasting cultural impact, reflected in the Slavic languages widely spoken in the region today. . . . Even present-day Peloponnesians carry a small yet significant amount of Slavic-related ancestry, but the ultimate origin of Slavic speakers and the degree of demographic impact in the region is not yet well understood.

A few caveats. First, the study is based on only 52 high quality DNA profiles, all of which come from three sites in Serbia. That's not a great data set for writing the whole history of the Balkans. (And two of them were identical twins, buried side by side.)

But for what's it's worth, this data matches closely with both the traditional narrative of Balkan history and the findings of recent genetic studies of the Roman empire. It is clear now that the establishment of the empire led to a great deal of movement between the eastern and western Mediterranean areas, and also north to south, with Africans found in Britain and Gauls in Egypt. For the people in the current study dated to between 1 and 250 AD, around half were mostly Anatolian or Syrian in their ancestry, while the rest were mainly descended from the local Iron Age folk. There were three exceptions, two men who proably came from northwestern Europe and one from Sudan or Ethiopia.

From 250 to 500 AD there was much less eastern Mediterranean ancestry, so those people either left or dwindled. Local Iron Age ancestry remained common. The new factor was several people carrying genes from northern Europe (resembling known Lombard graves) and others with components that resemble Sarmatians from the steppes. This matches with other modern genetic studies, which show evidence of major migrations from the north and northeast, enough people to leave clear genetic signatures in the medieval and modern populations.

Five individuals buried in the early 900s showed what is probably Slavic ancestry, with generally west Asian genes and Y-chromosomes from the group called I2-L621, which is common in modern Slavs but not found in Europe before the early Middle Ages.

This figure shows data from modern populations, with the black representing genes from northern or northeastern Europe (Goths. Lombards, Sarmatians, Slavs) and the white everything else. You can clearly see that the amount of northern and steppes DNA declines as you move south, just as you might expect. The tenth-century people from this study are outlined in red, showing that they fit fairly well into the modern gradient. 

The important lesson is that we humans are a species on the move, always migrating, invading, slave-trading, and otherwise mixing up our genes with spectacular abandon.