Stable European Population Structure

Of interest.

A Gab correspondent who is a friend of this blog alerts me to this paper, which broadly supports the Sallisian view of how modern European genetics correlates to racial history, and is not supportive of either leftist “constant panmixia leading to modern European mongrels” narratives or rightist ethnic fetishist narratives of “past migratory events in Europe, such as in the Roman Empire, only affected Southern Europe, particularly Italy, leaving modern Italians as non-White mongrels unconnected to ancient peoples, while the High Truster parts of Europe are 100% racially pure from the mists of prehistoric time.”

Excerpts (emphasis added) and my comments:

Abstract

Ancient DNA research in the past decade has revealed that European population structure changed dramatically in the prehistoric period (14,000-3,000 years before present, YBP), reflecting the widespread introduction of Neolithic farmer and Bronze Age Steppe ancestries. However, little is known about how population structure changed in the historical period onward (3,000 YBP - present). 

This latter period is the prime focus of ethnic fetishist (and leftist) solipsist “I say it so therefore it is true” narratives, so the data here are of particular interest.

To address this, we collected whole genomes from 204 individuals from Europe and the Mediterranean, many of which are the first historical period genomes from their region (e.g. Armenia, France). We found that most regions show remarkable inter-individual heterogeneity. Around 8% of historical individuals carry ancestry uncommon in the region where they were sampled, some indicating cross-Mediterranean contacts. Despite this high level of mobility, overall population structure across western Eurasia is relatively stable through the historical period up to the present, mirroring the geographic map. 

This is the key finding. While there were migratory movements and dispersals in Europe (and not only into Italy) throughout the historical period covered, the overall finding is that “despite this high level of mobility” (i.e., the migrations and dispersals), “overall population structure across western Eurasia is relatively stable through the historical period up to the present, mirroring the geographic map.” This is EXACTLY what I have been saying for years. Regardless of all the huffing and puffing of both ethnic fetishists on the right and anti-White activists on the left about historical migrations, ancient Rome, and other events (including the later “Moors”), the final genetic outcome is that there hasn’t been significant population change in the last 3,000 years; therefore, genes mirror geography in the expected pattern. Italians – including Southern Italians/Sicilians – are exactly where one would expect to find them with respect to the Europe-wide PCA-related correlation of genetic clines and geographical contours. Those Southern European groups are NOT found among MENA populations in PCA analyses. Therefore, we observe a “relatively stable” population structure from 3,000 YBP – present. The final outcome of all these population movements for today’s extant populations is that the effects of those movements are less than what has been popularly imagined.

We show that, under standard population genetics models with local panmixia, the observed level of dispersal would lead to a collapse of population structure. Persistent population structure thus suggests a lower effective migration rate than indicated by the observed dispersal. We hypothesize that this phenomenon can be explained by extensive transient dispersal arising from drastically improved transportation networks and the Roman Empire’s mobilization of people for trade, labor, and military. This work highlights the utility of ancient DNA in elucidating finer scale human population dynamics in recent history.

Actual migration was likely lower than what was previously estimated based on the presence of these outlier ancient samples. Given that modern Italy also falls within the expected PCA range, demonstrating relative population stability over time, the same "lower effective migration rate" likely applies to Italy as well, at least in areas outside of Rome itself (the city of Rome likely did have a significant influx, based on historical records, albeit perhaps not as much as some have suggested - and even there the long-term effect was such that the final outcome is relative stability of the population structure).

Introduction

…two major demographic transitions in prehistoric western Eurasia: first the farming transition ∼7,500 BCE (Lazaridis et al., 2014; Skoglund et al., 2012), and later the Bronze Age Steppe migrations ∼3,500 BCE (Haak et al., 2015)…most present-day European genomes can be modeled as a three-way mixture of these prehistoric groups: Western Hunter-Gatherers, Neolithic farmers, and Bronze Age Herders from the Steppe…By the end of the Bronze Age, the ancestry composition resembles that of present-day individuals. This suggests that the genetic landscape of present-day western Eurasia was largely established following the two major transitions, ultimately leading to the pattern observed today, where the genetic structure of Europe mirrors its geography…

Again – that is the KEY finding, and what I have been saying for years.  Differences among Europeans were for the most part established by these early founding events, not by popularized heavy breathing accounts of “Roman era slaves and migrants replacing Nordic Romans” or “Nordic Sicilians becoming dark mulattoes by mixing with Negroes.”

However, recent studies of historical period genomes from individual regions paint a picture of heterogeneity and mobility, rather than of stable population structure. In the city of Rome alone, the population was dynamic and harbored a large diversity of ancestries from across Europe and the Mediterranean from the Iron Age (∼1000 BCE) through the Imperial Roman period (27 BCE-300 CE) (Antonio et al., 2019). Historical genomes from the Iberian Peninsula also highlight gene flow from across the Mediterranean (Olalde et al., 2019).

These localized reports fit well with archaeological and historical records. By the Iron Age, sea travel was already common, enabling peoples from across the Mediterranean to come into contact for trade (Abulafia, 2011; Broodbank, 2013).

Subsequently, the Roman Empire leveraged its organization, labor force, and military prowess to build upon existing waterways and roads throughout Europe and create a united Mediterranean for the only time in history (Beard, 2015; Harper, 2017; Symonds, 2017). Not only did the Empire provide a means for movement, it also provided a reason for individuals to move. Empire building activities, broadly categorized into military, labor, and trade, pulled in people and resources from inside and outside the Empire (Scheidel, 2019).

To reconcile the expectation of overall demographic stability in western Eurasia with localized reports of heterogeneous, mobile populations, we sequenced 204 new historical period genomes from across Europe and the Mediterranean. By analyzing genetic similarities between individuals across historical Eurasia, we were able to quantify individual movements during this time. Based on population genetic simulations, we hypothesize how population structure may be maintained in the face of frequent individual dispersal.

So, the point is to reconcile the FACT of relative stability of time of European populations and the known migratory results that some ejaculate over.

Results

We collected whole genomes from 204 individuals across 53 archaeological sites in 18 countries spanning Europe and the Mediterranean (Figure 1 - figure supplement 1), 26 of these individuals were recently reported (Moots et al., 2022). This collection includes the first historical genomes from present-day Armenia, Algeria, Austria, and France. 

A majority of regions have highly heterogeneous populations in at least one historical time period…

Regional vignettes reveal various patterns of historical population structure. In Armenia, for example, the population is highly homogeneous at any given time (Figure 2). Across time periods, there are two distinct genetic clusters, corresponding to a temporal split around 772-403 BCE (Figure 2BC). The earlier cluster (C1) includes newly reported samples (n=5) from Beniamin and published ones (n=6) from five other sites. This cluster cannot be modeled by any single source of ancestry using existing data. The later cluster (C2), which contains newly reported samples (n=12) from Beniamin dating between 403 BCE-500 CE, is genetically similar to present-day Armenians (excluding two Kurdish individuals; Figure 2C). Despite the split, there is evidence of partial continuity between the earlier and later clusters: the later (C2) can be modeled using around 50% of the earlier cluster (C1) and an additional source of Steppe ancestry. 

Historical genomes from Northern Europe, particularly newly reported genomes from Lithuania and Poland, exhibit a similar level of homogeneity...

The Asian/Siberian migrations and admixture into Northern Europe predated this time period.

In contrast to the homogeneity of the Armenian population, most of the regions, including Italy, Southeastern Central Europe, and Western Europe, had strikingly heterogeneous populations. 

Note: Western Europe. While the more extreme Northern and Northeastern portions of Europe that were not part of the Roman Empire were not influenced by these specific events, it was not only Italy and Southeastern Central Europe that had “strikingly heterogeneous populations” – Western Europe had these as well. Thus, if Western Europe was able to emerge from this period without becoming “Levantine mongrels,” then why not Southern Europe as well?

Newly collected samples reinforce previous findings of high heterogeneity in Rome, including a large portion of the population having affinities for present-day Near Eastern populations (Antonio et al., 2019; Posth et al., 2021) (Figure 3 - figure supplement 1). Interestingly, Southeastern Central European and Western European individuals during the Imperial Roman & Late Antiquity period also exhibit high heterogeneity, on par with that of contemporaneous Italy (Figures 3 and 4).

Again – whatever you want to say about Roman-era population heterogeneity in Italy, it was ALSO found in the Western European parts of the Empire and surrounding regions. Included were some MENA outliers in Austria/Germany (the source of Hitler’s NRY?).

Furthermore, these ancestries are often shared across regions. In Southeastern Central Europe, a core group of individuals have ancestry similar to that of present-day and contemporaneous Central Europeans (C10), while other clusters have ancestry similar to that of Northern Europeans (C4) and Eastern Mediterraneans (C6) (Figure 3C). These ancestry groups are found in contemporaneous Italy and Western Europe as well (Figure 4C, Figure 3 - figure supplement 1). We also observe outliers of eastern nomadic ancestry, similar to that of Sarmatian individuals previously reported, in both Western Europe (C5, n=2) and Southeastern Central Europe (C1, n=2).

Again, not only in Italy. Heterogeneity was found in other areas of the Empire and in areas close by, including in Western Europe.

At least 8% of historical individuals are ancestry outliers

If you listen to the ethnic fetishists, you’d think that 80% of the population of Italy were “outliers” and Western Europe was mysteriously untouched and pristine.

This network reveals the interconnectedness of Europe and the Mediterranean during the historical period. For example, as discussed above, the Armenian population is quite homogeneous (Figure 2). Unsurprisingly, no outliers were found within Armenia; however, we found outlier individuals in the Levant, Italy, and North Africa who can be putatively traced back to Armenia according to their ancestry (Figure 5C; blue outgoing arrows from Armenia). In contrast, the heterogeneous population in Italy connects it to many other regions, with bi-directional movement in most cases.

Note – bidirectional movement with respect to Italy, not just an influx. Thus, as some have suspected, some limited similarities that may be found today between outliers in distinct populations may be from bidirectional, not unidirectional, flow.

In North Africa, outliers found in Iron Age Tunisia (Moots et al., 2022) indicate movements from many regions in Europe, and reciprocal North African-like outliers were found in Italy and Austria (Western Europe). North African ancestry in Italy is supported by a single previously reported individual from the Imperial Roman period (R132) (Antonio et al., 2019). Similar North African ancestry in Western Europe is supported by a single individual, R10667, from Wels, Austria, a site located on the frontier of the Roman Empire (C18 in Figure 4). This individual from Austria can be modeled using Canary Islander individuals from the Medieval Ages or an Iron Age outlier (distinguished by having more sub-Saharan ancestry) from Kerkouane, a Punic city near Carthage in modern-day Tunisia.

The estimate of 8% should be considered conservative for the proportion of “non-local” individuals. 

OK, but it is not 80% or some other absurdly high number.

Spatial population structure is relatively stable in the last 3,000 years

The remarkable amount of heterogeneity and mobility in the historical period leads to the question of what impact this might have had on population structure over time. To investigate this, we sought to quantify the overall change in population structure across time, from prehistoric to present-day. To assess spatial structure of population differentiation, we calculated FST across groups of individuals on a sliding spatial grid in each time period and related it to their mean geographic distance. In each time period, we recovered the classical pattern of isolation-by-distance (Figure 6A), where individuals closer in geographic space are also more similar genetically. Across time periods, we see a large decrease in overall FST from the Mesolithic & Neolithic periods to the Bronze Age (approximately 10,000-2300 BCE), coinciding with the major prehistoric migrations (Haak et al., 2015; Lazaridis et al., 2014). From the Bronze Age onward, however, FST does not decrease further with time, indicating that the level of genetic differentiation across space is relatively stable from the Bronze Age to present-day.

The importance of this finding cannot be overstated. The major shifts in Fst vs. geographic distance occurred during the early founding events of European ethnogenesis; on the other hand, “the level of genetic differentiation across space is relatively stable from the Bronze Age to present-day.” The very ancient events were important; the historic events that some people go into onanistic frenzies about much less so. The PCA of Fig 2-S1 shows modern Western Eurasian populations, and clearly demonstrates the genes mirror geography paradigm.

To assess not only the amount, but also the structure of geographic population differentiation, we compared the “genetic maps” of historical period and present-day genomes. To construct these “maps”, we performed principal component analysis on all 1713 present-day European and Mediterranean genomes sampled across geographical space (Figure 6B) and projected historical period genomes onto the same PC space. Echoing close correspondence between genetic structure and geographic space in present-day Europeans (Novembre et al., 2008), we recovered similar spatial structure for historical samples as well, although noisier due to a narrower sampling distribution and higher local genetic heterogeneity (Figure 6C).Together, our analyses indicate that European and Mediterranean population structure has been relatively stable over the last 3,000 years.

In case any of the Nordicist ethnic fetishists missed that – “...our analyses indicate that European and Mediterranean population structure has been relatively stable over the last 3,000 years.”

This raises the question: Is it surprising for stable population structure to be maintained in the presence of ∼8% long-range migration? To address this, we simulated Wright-Fisher populations evolving neutrally in continuous space. In these simulations, spatial population structure is established through local mate choice and limited dispersal, which we calibrated to approximately match the spatial differentiation observed in historical-period Europe (Figure 6A, Figure 7A and Figure 7 - figure supplement 1, maximum FST of ∼0.03). We then allowed a proportion of the population to disperse longer distances, empirically matching the migration distances we observed in the data during the historical period (Figure 7 - figure supplement 2). Even with long-range dispersal as low as 4%, we observe decreasing FST over 120 generations (∼3000 years with a generation time of 25 years) as individuals become less differentiated genetically across space (Figure 7B). At 8%, FST decreases dramatically within 120 generations as spatial structure collapses to the point that it is hardly detectable in the first two principal components (Figure 7C). These simulations indicate that under a basic spatial population genetics model we would expect structure to collapse by present-day given the levels of movement we observe.

So, given the level of dispersion, over time, you would expect population structure to "collapse" as gradual panmixia occurs. But this did NOT happen. On to the Discussion to observe the authors speculate on why the population structure was in fact maintained, even in the face of 8% (or more) population dispersion. 

Discussion

In summary, we observed largely stable spatial population structure across western Eurasia and high mobility of people evidenced by local genetic heterogeneity and cross-regional connections. These two observations are seemingly incompatible with each other under standard population genetics assumptions.

A possible explanation for this apparent paradox is that our simulations did not capture some key features of human behaviors and population dynamics. In the populations we simulate, migration implies both movement and reproduction with local random mate choice. However, in real human populations migration can be more complex: people do not necessarily reproduce where they migrate, and reproduction is not necessarily random. We hypothesize that in the historical period there was an increasing decoupling of movement and reproduction, compared to prehistoric times. 

As some more sane people have suggested, slaves and migrants may not have been successfully reproducing; and if they did reproduce, did not significantly affect native populations. They may have mostly mated among themselves in major urban centers, and those population crashed after the fall of the Western Roman Empire, being repopulated by native rural populations. And even if there was some mixture between natives and intrusive elements in Rome (and, possibly, in some Etruscan settlements and elsewhere), these areas would have become depopulated and then repopulated by native stocks.

According to a longstanding historical hypothesis, the Urban Graveyard Effect, the influx of migrants in city-centers disproportionately contributed to death rate over birth rate; a process which would contribute to observing individuals as “transient” migrants…

Urban migrants and slaves were dying off, and replaced by other transients, and/or by a native rural influx.

With transient mobility as the main contributor to the observed heterogeneity, it remains unclear what additional demographic processes contributed to the maintenance of spatial genetic structure. The collapse of the Empire involved a loss of urban-military complexes and depopulation of cities, followed by ruralization (Burgess, 2007; Dey, 2015; Roymans et al., 2020). Without the Empire incentivising trade and movement, there may be little motive for individuals to remain in these now remote regions.

The population of cities like Rome collapsed after the fall of the Western Roman Empire.  Repopulation was to a large extent by natives.

If this hypothesis is true, we would expect a reduction in local genetic heterogeneity after the collapse of the Empire. Unfortunately, we do not have this period sampled densely enough to assess this comprehensively. The lack of samples is further amplified by the fact that ancient DNA comes from archaeological excavations, which tend to be enriched in urban areas; a stone mausoleum in the city center, for example, will produce more surface scatter than a wood farmhouse, making urban areas more likely for excavation (Bowes, 2011). This makes it difficult to comprehensively address differences in rural versus urban demography. Collecting more genetic data from both urban and rural contexts across the historical period will be a valuable future step in understanding how spatial population structure was maintained. Furthermore, it could elucidate the role of other historical events and peoples, such as the Franks, Lombards, Visigoths, and Huns, during the Migration Period.

OK.

Based on genetic analyses and the rich historical record, we hypothesize that both the loss of transient migrants which contributed to population heterogeneity, as well as repopulation by less heterogeneous, but temporally stable, local populations could have helped maintain overall stability of genetic structure from the Iron Age to present-day. 

Exactly.

This work highlights the utility of ancient DNA in revealing complex population dynamics through direct genetic observations through time and the importance of integrating historical contexts to understand these complexities.

By the way, the PCA of Figure 3-S1 shows that present day Italian genomes fall in the same space as the non-outlier ancient samples; the outlier samples are outside the modern Italian range. 

In summary:

• 1.The differences between Europeans observed today are mostly the result of the founding events of European ethnogenesis involved the hunter-gatherers, Neolithic farmers, and Steppe incursions, not from later-day historical events that the “movement” loves to fantasize about.
• 2. Population heterogeneity in the days of the Roman Empire existed in Western Europe as well as in Italy and in areas of the Empire further to the south and east. "Movement" fantasies about their favorite areas of Europe being pristine with respect to non-European migrants until relatively recently need to be reconsidered.
• 3. The major finding is that there is a relatively stable population structure in Europe from 3,000 YBP – present, despite the aforementioned population heterogeneity.  This is reflected in "genes mirror geography" in PCA and in the relatively stable Fst vs. geographic distance over the last 3.000 years. The authors then speculated as to why the heterogeneity (not as large as some fantasize about) did not significantly affect population structure.  Regardless of the reasons, the facts remain as they are - relative stability over the past 3,000 years.

Now, of course, all of this does not mean that no changes took place at all.  Obviously, over a period of thousands of years, some demographic events and changes occurred. However, the final outcome of all of these events has been a remarkable degree of (relative) stability of European population structure. There is no evidence for significant changes, looking at current populations compared to the founding stocks of 3,000 YBP; some insignificant changes, yes, a few percentage points of ancestry here and there, perhaps, but the idea of widespread race replacement and/or mongrelizing admixture radically changing populations to those extant today - there is no evidence for that. The evidence says otherwise.

However, we should not let past history make us optimistic about current trends. There are fundamental differences with the current situation that bodes ill for long-term stability of European population structure. Today, we have continuous mass immigration, both legal and illegal, coupled to below-replacement native fertility and higher alien fertility - the opposite of what seems to have occurred in ancient times. The migrants of today are not transient - in the absence of radical action on the part of the natives, the migrant populations seem permanent and they are expanding. It is unlikely that there will be depopulation of cosmopolitan urban areas followed by repopulation of those areas by fertile rural natives - indeed, the opposite seems to be the case as the aliens are in some cases expanding into the countryside. Any possibility of stabilizing European population structure today will require political (in all the meaning of the word) action, not a misguided hope that future demographic trends will mirror those of ancient times.