High-resolution stuff

I just emailed this to the authors of High-resolution genomic ancestry reveals mobility in early medieval Europe, a new preprint at bioRxiv [LINK].

I appreciate that Polish population history is not the main focus of your preprint, and also that you're constrained by the lack of relevant and suitably high quality ancient genomes from East-Central and Eastern Europe. However, I must say that your analysis of the Medieval Polish population and resulting conclusions about Polish population history don't reflect reality.

Your Poland_Middle_Ages genomic cluster is made up of just six samples that don't fully represent the genetic complexity of the core population of Medieval Poland.

As a result, you classified PCA0148 as one of the Poland_Middle_Ages outliers, even though this sample isn't an outlier when analyzed within the context of the full set of published Polish Medieval genomes.

Moreover, PCA0148 is very similar to several Polish Viking Age samples that show Scandinavian-specific genome-wide and Y-chromosome haplotypes, and probably likewise shows some Scandinavian-related ancestry.

This is important to note when attempting to recapitulate Polish population history, because it suggests that Scandinavian-related ancestry played a formative role in the shaping of the core Polish Medieval genetic cluster.

Thus, you might be correct when you claim that the six samples in your Poland_Middle_Ages cluster don't show any "detectable" Scandinavian-related ancestry, but this doesn't necessarily mean that this type of ancestry isn't a key part of the post-Iron Age Polish population history.

Below is a self-explanatory Principal Component Analysis (PCA) plot that illustrates my points. Interestingly, Figure 3c in your preprint shows very similar outcomes in regards to the post-Iron Age Polish population history. But the style and scale of your figure makes it difficult to spot the subtle but likely genuine Northwest European-related genetic shifts shown by PCA0148, the Viking context samples and present-day Poles relative to the Poland_Middle_Ages cluster.

However, I'm also skeptical that your Poland_Middle_Ages cluster doesn't carry any detectable or even significant Scandinavian-related ancestry. That's because I suspect that there might be some technical issues with your analysis that are masking this type of ancestry in the Polish samples.

Your top mixture model for the Poland_Middle_Ages cluster is, in all likelihood, an extreme statistical abstraction of reality, rather than a close reflection of it. That's because, due to a combination of historical, geographical and genetic factors, neither Italy.Imperial(I).SG nor Lithuania.IronRoman.SG are realistic formative source populations for the Medieval Polish gene pool.

One of the reasons why you ended up with such a surprising result is probably the lack of suitable samples from East-Central and Eastern Europe, especially those associated with plausibly the earliest Slavic-speaking populations.

It's also possible that basing your mixture model on formal statistics played a key part.

Formal statistics-based mixture models are known to be biased towards outcomes involving mixture sources from the extremes of mixture clines. If your analysis is affected by this problem, then this would help to explain why you characterized the Poland_Middle_Ages cluster as simply a two-way mixture between a Middle Eastern-related group from Imperial Rome and a Baltic population with a very high cut of European hunter-gatherer ancestry.

I do note that on page 6 of your manuscript you consider the possibility that the Southern European-related signal in the Poland_Middle_Ages cluster might only be very distantly related to Italy.Imperial(I).SG, and that it may even have spread across Poland with early Slavic speakers. This is a great point, and I think it should be emphasized and expanded upon, because I suspect that the problem runs deeper than this.

For instance, if the early Slavic ancestors of Poles carried substantially more Southern European-related ancestry than Lithuania.IronRoman.SG, and this ancestry was, say, more Balkan-related than Italian-related, then this might radically change your modeling of the Poland_Middle_Ages cluster. That's because these early Slavs would be positioned in a very different genetic space than Lithuania.IronRoman.SG, which could potentially require a significant signal of Scandinavian-related ancestry to get a robust mixture model.

Finally, it might be useful to consider Isolation-by-Distance as a partial vector for the Italy.Imperial(I).SG-related signal in Medieval Poland.

The full set of published Polish Medieval genomes includes a number of outliers with obvious ancestry from Western Europe and the Balkans. These people probably don't represent any large-scale migrations into Poland, but rather the movements of individuals and small groups. Over time, such small-scale mobility may have had a fairly significant impact on the genetic character of the Polish population.

Update 26/03/2024: I sent another email to Speidel et al., this time in regards to their analysis of present-day Hungarians.

Your preprint also claims that present-day Hungarians are genetically similar to Scythians, and that this is consistent with the arrival of Magyars, Avars and other eastern groups in this part of Europe.

However, present-day Hungarians are overwhelmingly derived from Slavic and German peasants from near Hungary. This is not a controversial claim on my part; it's backed up by historical sources and a wide range of genetic analyses.

Hungarians still show some minor ancestry from Hungarian Conquerors (early Magyars), but this signal only reliably shows up in large surveys of Y-chromosome samples.

The Scythians that you used to model the ancestry of present-day Hungarians are of local, Pannonian origin, and they don't show any eastern nomad ancestry. So they're either acculturated Scythians, or, more likely, wrongly classified as Scythians by archeologists.

And since these so-called Scythians lack eastern nomad ancestry, the similarity between them and present-day Hungarians is not a sign of the impact from Avars, Hungarian Conquerors and the like, but rather a lack of significant input from such groups in present-day Hungarians.

Citation...

Speidel et al., High-resolution genomic ancestry reveals mobility in early medieval Europe, bioRxiv, Posted March 19, 2024, doi: https://doi.org/10.1101/2024.03.15.585102

See also...

Wielbark Goths were overwhelmingly of Scandinavian origin

Wielbark Goths were overwhelmingly of Scandinavian origin

When used properly, Principal Component Analysis (PCA) is an extraordinarily powerful tool and one of the best ways to study fine-scale genetic substructures within Europe.

The PCA plot below is based on Global25 data and focuses on the genetic relationship between Wielbark Goths and Medieval Poles, including from the Viking Age, in the context of present-day European genetic variation.

I'd say that it's a wonderfully self-explanatory plot, but here are some key observations:

- the Wielbark Goths (Poland_Wielbark_IA) and Medieval Poles (Poland_Middle_Ages) are two distinct populations

- moreover, the Wielbark Goths form a relatively compact Scandinavian-related cluster and must surely represent a homogenous population overwhelmingly of Scandinavian origin

- on the other hand, the Medieval Poles form a more extensive and heterogeneous cluster that overlaps with present-day groups all the way from Central Europe to the East Baltic, and that's because they are likely to be in large part of mixed origin

- I know for a fact that at least some of these early Poles harbor recent admixture, because their burials are similar to those of Vikings and their haplotypes have been shown to be partly of Scandinavian origin (see here)

- one of the Wielbark females is an obvious genetic outlier (Poland_Wielbark_IA_outlier), and basically looks like a first generation mixture between a Goth and a Balt.

Please note that the PCA is only based on relatively high quality genomes, so as not to confuse the picture with spurious results and noise. Also, all outliers with potentially significant ancestry from outside of Central, Eastern and Northern Europe were removed from the analysis. The relevant datasheet is available here.

However, sanity checks are always important when studying complex topics like fine-scale genetic ancestry. To that end I've prepared a graph based on f3-statistics of the form f3(X,Cameroon_SMA,Estonia_BA)/(X,Cameroon_SMA,Ireland_Megalithic), that reproduces the key features of my PCA. The relevant datasheet is available here.

Polish groups from the Middle Ages are marked with the MA suffix, while the Iron Age Wielbark Goths are marked with the IA suffix.

If you're wondering why I plotted the f3-statistics that I did, take a look at this (all groups largely of Scandinavian origin are emboldened):

f3(X,Estonia_BA,Cameroon_SMA)
Poland_Legowo_MA 0.226406
Poland_Ostrow_Lednicki_MA 0.225996
Poland_Plonsk_MA 0.225017
Poland_Trzciniec_Culture 0.224215
Poland_Lad_MA 0.224142
Poland_Viking 0.223838
Poland_Niemcza_MA 0.223659
Poland_Weklice_IA 0.223549
Poland_Kowalewko_IA 0.222584
Poland_Pruszcz_Gdanski_IA 0.222324
Sweden_Viking 0.222091
Russia_Viking 0.222042
Poland_Maslomecz_IA 0.221914
Norway_Viking 0.221825
Denmark_EarlyViking 0.221257
Denmark_Viking 0.221174
England_Viking 0.220979

f3(X,Ireland_Megalithic,Cameroon_SMA)
Poland_Maslomecz_IA 0.219816
Poland_Weklice_IA 0.219501
Denmark_Viking 0.2192
Poland_Kowalewko_IA 0.219176
Poland_Ostrow_Lednicki_MA 0.218916
Norway_Viking 0.218854
Poland_Pruszcz_Gdanski_IA 0.218684
Sweden_Viking 0.218626
Denmark_EarlyViking 0.218529
England_Viking 0.218308
Russia_Viking 0.217999
Poland_Viking 0.217914
Poland_Plonsk_MA 0.217756
Poland_Lad_MA 0.217719
Poland_Legowo_MA 0.21765
Poland_Niemcza_MA 0.217001
Poland_Trzciniec_Culture 0.216551

Interestingly, the Middle Bronze Age samples associated with the Trzciniec Culture (Poland_Trzciniec_Culture) show a closer genetic relationship to Medieval Poles than to Wielbark Goths or Northwestern Europeans. This is indeed the case both in terms of genome-wide and uniparental markers, including some very specific lineages under Y-chromosome haplogroup R1a.

But that's a much more complex issue that I'll leave for another time. So please stay tuned.

See also...

Slavs have little, if any, Scytho-Sarmatian ancestry

My take on the Erfurt Jews

I had a quick look at the genotype data from the recent Waldman et al. preprint focusing on the ancestry of early Jews from Erfurt, Germany. My impression is that the genetic origins of these Jews are somewhat more complex than claimed in the manuscript.

Indeed, I'd say the Waldman et al. characterization of the Erfurt Jews as a three-way mixture between populations similar to present-day Lebanese, South Italians and Russians doesn't exactly reflect reality.

Unlike Waldman et al., I designed an ADMIXTURE analysis that separated East Asian ancestry into East Asian and Siberian clusters, and also included Mediterranean and North African clusters. The output is available in a spreadsheet HERE. Below is a bar graph based on some of the output.

Now, keeping in mind that ADMIXTURE is not a formal mixture test, and that it estimates ancestry proportions from inferred populations, as opposed to ancient groups that actually existed, here are some key observations:

- in terms of fine scale ancestry, the Erfurt Jews show enough variation to be divided into three or four clusters, as opposed to just two as per Waldman et al.

- some of the Erfurt Jews show excess "Mediterranean" ancestry, while others excess "North African" ancestry, and this cannot be explained with ancestral populations similar to Lebanese and/or South Italians, but rather with significant gene flow from the western Mediterranean and possibly North Africa

- several of the Erfurt Jews show relatively high levels of "East Asian" ancestry that cannot be explained by admixture from Russians, or even any Russian-like populations, because such populations almost lack this type of ancestry, and instead show significant "Siberian" admixture

- as far as I can see, there are no correlations between any of the observations above and the quality of the samples. That is, low coverage doesn't appear to be causing the aforementioned excess "Mediterranean", "North African" and/or "East Asian" ancestry proportions.

Investigating this in more detail with, say, formal statistics will take some time. But I was able to reproduce the results from the above ADMIXTURE run using several somewhat different datasets, so that's something.

It seems to me that Waldman et al. want a simple and elegant model to explain the data, which is understandable, but I do think they should at least expand their ADMIXTURE analysis to include "Siberian", "Mediterranean" and "North African" clusters, and go from there depending on what they find.

Citation...

Waldman et al., Genome-wide data from medieval German Jews show that the Ashkenazi founder event pre-dated the 14th century, bioRxiv, posted May 16, 2022, doi: https://doi.org/10.1101/2022.05.13.491805

See also...

Mediterranean PCA update

Asiatic East Germanics

Around a third of the ancient individuals in my dataset associated with East Germanic-speaking cultures show obvious ancestry from Central and/or West Asia.

This shouldn't be too surprising, considering, for instance, the well documented contacts between East Germanic tribes and the Avars, Huns, Sarmatians and other nomadic groups that streamed into Europe from the Asian steppes during the Migration Period. It's a topic that I've raised before at this blog (see here).

But the curious thing is that very little, if any, of this ancestry has percolated down to present-day Europeans.

The easiest way to show this is with a Principal Component Analysis (PCA) based on my Global25 data. The relevant PCA datasheet can be downloaded here. Basic details about the ancient samples in the analysis are available here.

Some of the Northeastern European populations, particularly the Uralic speakers, appear to be attracted to the Hunnic cluster. However, this is mostly an artifact of pre-Migration Period east to west population expansions in the far north of Europe, probably including those of the Proto-Uralians (see here).

So how is it that, despite ruling over vast areas of Europe for hundreds of years, the East Germanics appear not to have contributed significantly to the present-day European gene pool? My theory is that, much like the Avars and Huns, they were militarily and demographically overwhelmed by the ascending groups around them, such as the Slavs, and they simply went extinct.

To wrap things up, here's a basic qpAdm mixture model designed to test for Hunnic-related ancestry in a few Eastern and Northern European populations of interest. Note the significant slice of this type of ancestry in the likely early Goths of the Chernyakhiv culture. Is it real? Feel free to share your thoughts in the comments below.

UKR_Chernyakhiv
DEU_MA 0.863±0.038
Hun_Tian_Shan 0.137±0.038
chisq 12.525
tail prob 0.325466
Full output

Swedish
Baltic_EST_IA 0.126±0.078
DEU_MA 0.849±0.073
Hun_Tian_Shan 0.025±0.020
chisq 8.338
tail prob 0.595877
Full output

Ukrainian
Baltic_EST_IA 0.121±0.064
DEU_MA 0.857±0.060
Hun_Tian_Shan 0.022±0.017
chisq 11.458
tail prob 0.322956
Full output

Estonian
Baltic_EST_IA 0.597±0.069
DEU_MA 0.373±0.064
Hun_Tian_Shan 0.030±0.017
chisq 15.739
tail prob 0.107361
Full output

See also...

Conan the Barbarian probably belonged to Y-haplogroup R1a

More on the association between Uralic expansions and Y-haplogroup N

Uralic-specific genome-wide ancestry did make a signifcant impact in the East Baltic