Early Slavs from Tribal Period Poland

A paper dealing with the origin of Slavic speakers, titled Ancient DNA connects large-scale migration with the spread of Slavs, was just published at Nature by Gretzinger et al. (see here).

The dataset from the paper includes eight fascinating ancient samples from Gródek upon the Bug River in Southeastern Poland. These individuals are dated to the so called Tribal Period (8th –9th centuries), and, as far as I know, they represent the earliest Slavic speakers in the ancient DNA record.

The really interesting thing about these early Slavs is that they already show some Germanic and other Western European-related ancestries.

In the Principal Component Analysis (PCA) plots below, three of them cluster near present-day Ukrainians, while the rest are shifted towards present-day Northwestern, Western and Southern Europeans. The plots were produced with the excellent Vahaduo G25 Global Views tool using the data here.

These results aren't exactly shocking, because the people who preceded the early Slavs in the Gródek region were Scandinavian-like and associated with the Wielbark archeological culture. In other words, they were probably Goths who also had significant contacts with the Roman Empire.

However, it's not a given that the ancestors of the Tribal Period Slavs mixed with local Goths. It's also possible that they brought the western admixture, or at least some of it, from the Slavic homeland, wherever that may have been.

That's because the early Slavs who migrated deep into what is now Russia also showed Western European-related admixture. This is what Gretzinger et al. say on page 74 of their supplementary info (emphasis is mine):

The only deviation from this pattern is observed for ancient samples from the Russian Volga-Oka region, where we measure higher genetic affinity between present-day Southern/Western Europeans and the SP population compared to the pre-SP population (Fig. S17). This agrees with the pattern observed in PCA and ADMIXTURE that, in contrast to the Northwestern Balkan, Eastern Germany, and Poland-Northwestern Ukraine, the arrival of Slavic-associated culture in Northwestern Russia was associated with a shift in PCA space to the West, a decrease of BAL [Baltic] ancestry, and the introduction of Western European ancestries such as CNE [Continental North European] and CWE [Continental Western European].

Thus, it's highly plausible that the Tribal Period Slavs from Gródek were very similar, perhaps even practically identical, to the proto-Slavs who lived in the original Slavic homeland. Hopefully we won't have to wait too long to discover whether that's true or not. More Migration period and Slavic period samples from the border regions of Belarus, Poland and Ukraine are needed to sort that out.

On the other hand, most of the post-1000 CE individuals from Gródek are shifted closer to present-day Balts. This is probably due to admixture from nearby Baltic-speaking populations. At the time, Baltic speakers still occupied much of northern and eastern Poland.

I'm still going through the Gretzinger et al. paper and I'll probably have a lot more to say about it in the near future.

However, unfortunately, I've already spotted a silly mistake in the supplementary info that will probably have some very annoying consequences for us on this blog. On page 109 the authors make the false claim that South Asian ancestry is present in a wide range of ancient Eastern European and Central Asian populations from the Bronze Age to the Scythian period.

Furthermore, Sycthian groups from Ukraine show varying fractions of South Asian ancestry (between 5% and 12%), a component present in many ancient individuals from Moldova (e.g. Moldova_IA, Moldova_LBA and Moldova_MBA), Ukraine (Ukraine_Alexandria_MBA and Ukraine_BA_Catacomb.SG), Western Russia (e.g. Russia_EarlySarmatian.SG, Russia_MLBA_Potapovka, or Russia_MLBA_Sintashta) and the Caucasus (Russia_Caucasus_LBA_Dolmen and Russia_North_Caucasus_MBA) but (nearly) absent in the SP genomes from Central and East-Central Europe (<5%) (Fig. S42b).

All ancient and present-day South Asian populations carry what is commonly known as Ancestral South Indian (ASI) ancestry, while all of the above mentioned ancient groups lack it. Ergo, it's impossible for these ancients to have actual South Asian ancestry.

What happened is that Gretzinger et al. created a genetic component in ADMIXTURE based on present-day South Asians. However, South Asians today have very complex ancestry from several different sources, including early pastoralists from the North-Pontic steppe in Eastern Europe and early farmers from Central Asia and what is now Iran. As a result, the groups that share significant amounts of alleles with South Asians via these sources also show so called South Asian ancestry in the Gretzinger et al. analysis.

Unless this problem is corrected we're likely to see some nutjobs online using this paper to claim all sorts of nonsense about the origins of ancient Eastern Europeans and Central Asians, especially the Sintashta people and Scythians.

See also...

High-resolution stuff

Leo Speidel & Pontus Skoglund