North African Neolithic was influenced by Europe... and European Chalcolithic by Iberian Neolithic

Or so it seems considering the data of Fregel et al., a study I have in my to-do list for some time and that I don't see cited often or ever at all.

Rosa Fregel et al., Neolithization of North Africa involved the migration of people from both the Levant and Europe. BioRxiv 2017 (pre-pub). DOI:10.1101/191569

The critical piece is probably this selection from Admixture results but which repeats over and over through the study with many more analyzed populations from all West Eurasia and North Africa:

We see how KEB (Morocco Neolithic) is a mix of European Neolithic intermediate between Iberia (purple) and Sardinian (blue) on one side and, on the other, something like Mozabites (not shown in this detail, cream). TOR is a new Neolithic sample from Andalusia.

Another ancient Moroccan sample IAM (pre-Neolithic, not shown here either) is fully cream-colored like mostly are modern Mozabites. 

Interestingly we see for the first time the emergency of a purple-colored component that differentiates Iberian Early Neolithic from the rest (although this does not happen at lower K-values, so they are still related), a component that, in the MNChL (Middle Neolithic and Chalcolithic) period, somehow appears as dominant in Italy (no data for earlier times) and becomes quite dominant in Central Europe. 

This is intriguing to say the least. It must be said that modern Sardinians and Basques (these probably, not labeled) are low in the purple component, although less than other populations, and that somehow the Early Neolithic (blue) component made a comeback:

I do not want to over-interpret all this (autosomal genetics are not an exact science) but, judging on KEB, the purple component is not just a generic southern branch (Cardium Pottery) distinction but something specifically Iberian or Italo-Iberian. The matter needs more research but it is in any case very intriguing that the purple component seems to expand from Iberia or somewhere nearby (France?, Italy?) in the period leading to the Chalcolithic, a most critical one in the formation of the genetics of Europe.

There is a also a little hoard of DNAmt and Y-DNA, with G2a-M201 (in Europe), E1b-L19* (in pre-Neolithic North Africa) and T-M184 (in Neolithic North Africa) in the patrilineal side and quite a bit of varied K1a in the matrilineal one, as well as JT (also in both shores) and U6 and M1 in North Africa.

Worth reading and keeping in mind, no doubt.

Iberian genetic clusters

I've been the last two weeks or so chewing on this pre-pub and there's a point when no more chewing seems to be useful. So let's get to discuss it as well as possible.

Clare Bycroft et al. Patterns of genetic differentiation and the footprints of historical migrations in the Iberian Peninsula. BioRxiv 2018 (pre-pub. DOI:10.1101/250191

The key finding is clustering of the populations of the Iberian Peninsula as in this map (locations for the Spanish state are precise, for Portugal unknown and located at random, also shadowing for Portugal is uniform for all the country):

Supp. Figure 1a

The weirdest thing for me is that the Catalan-Alacant and Seville-León-Asturias cluster are strongly related in the cladogram. I'll discuss this below.

Another very weird feature is the presence of a group in Pontevedra province (Galicia) that is the most different of all, even more distinct than Basques. It is composed of many small highly endogamous subgroups. I do not have at the moment any explanation for this, honestly.

External influences: mostly "French"

When factored as made up external populations, Iberians are mostly French (or something that approaches that label), although "mostly" varies from c. 60% in the West to c. 90% in Gipuzkoa. This pattern of "Frenchness" reminds that of the distribution R1b-S116. Correlation is not causation but it is still correlation and when R1b-S116 seems to stem from somewhere France and arrive to the Peninsula at least as early as the Bronze Age (or maybe before but still undetected, terminus ante quem at Los Lagos, as discussed recently). 

Supp. Fig 5a

The most affected population by this French influence are Basque1, which show no significant contribution from any other source (only very small from Italy1 and very tiny from North Morocco, see supp. fig. 7) but the authors say that (supp. info.):

Notably, the Basque-centred cluster has a markedly different profile from the rest. Firstly, it has much lower, or zero contributions from donor groups that contribute to all other clusters: Italy, NorthMorocco, and WesternSahara, and a very large contributionof 91% (88-93) from France. Additionally, the model fit for this cluster is strikingly less good than that for the other clusters (Supplementary Figure 4d), suggesting that Basque-like DNA is less well captured by the mixture of donor groups in this data set. Specifically the Basque share even more DNA with the French group than predicted by their mixture representation, which might reflect, for example, that the DNA the Basque share with present-day French is only a subset of modern French ancestry. This pattern is seen for other Spanish groups also, but to a much lesser extent.

Area that demands urgent genetic research

So it seems we may be dealing with some sort of "paleo-French" rather than modern Indoeuropeanized French. 

All genetic roads lead to France, at least in Western Europe: it also happens in Great Britain and Ireland, and it is very apparent in the geographically sorted phylogeny of R1b-S116. And is also this area where we see the earliest signs of mitochondrial DNA "modernity": in Paternabidea (Navarre) and Gurgy (Burgundy), an area that demands much greater attention from genetic and archaeogenetic research than has received to this day. 

The other major contributors are: Italy (mostly Italy1), with peaks of c. 20% and influencing mostly the South and Center, North Morocco, with peak of c. 10% in Portugal and a West and South distribution, and Ireland, with peak of c. 6% in Eastern Asturias and a broadly Western distribution. 

Italian contribution (Italy1)

North Morocco contribution

Ireland contribution

What do exactly these contributor components mean? Hard to say, although part of the Italian and North Moroccan elements could well be related to historical episodes such as Roman and Muslim conquests. But only partly so,because the North African in Galicia just cannot be that high only from a Muslim conquest that was very limited in time, nor should we expect to be that much "Muslim" nor "Roman" in the remote and largely ignored area of modern Portugal: there must be more ancient origins, probably dating to the Neolithic, Chalcolithic or Bronze Age. 

minor West Sahara contribution

And in the case of the North African component we may have a guide in a minor West Saharan contribution (at right), which may well reflect an older and "purer" form of North Africanness and which is againcon centrated in Portugal and Galicia, with extension to parts of the Central Plateau but does not affect the South, the area where we should expect most of the Muslim period's genetic influence. 

We cannot trace a line in Portugal because of the uncertainty of the geographic origins of the samples but we can do it within the boundaries of Spain and that line suggests that the Muslim genetic influence could be intense by the Southern third and maybe all the way to Zamora by the Western part but should not be relevant in Galicia nor Asturias nor (inferred, uncertain) much of Portugal. That in these areas, the North African element is peculiar and looks older than the Emirate/Caliphate of Cordoba. 

Speculating on the possible origins of the Iberian clusters

This part has given me a true headache. It is very hard to understand how these clusters formed and I will not pretend here that I have all the answers. The most strange of all is the affiliation of the Central-West and Eastern clusters. 

The problem is not only the highly implausible relation between Asturias-León and West Andalusia, which the authors seem to believe product of historical colonization at the time of the Reconquista (13th century) but which makes no sense whatsoever because the Kingdom of Seville was never part of the barely autonomous Kindgom of León but an administrative division of Castile (of which León was by then just a dependency) and we should thus see at least some important influence of the Central (yellow triangles) cluster, which is dominant in Valladolid, Madrid and even the city (but not the countryside) of Burgos, and we do not see anything like that. 

One possibility is of course that the components or some of them are not that real but I do not see any indication of that in the study, so, in wait of independent replication, I'll take them at face value. 

So why then? I've been scratching my head until I could not think any further, I swear. 

And this is my hypothesis, risky as it may be:

1. The essence of the split between the related Spanish components (excluding Galicians and Basques) and the Portuguese-Galician component could be at the Early Neolithic. When I mask the areas not or weakly affected by the Earliest Neolithic in the components map I get this:

... what seems to correspond odly too well to the first major split in the cladogram between the Portuguese-Galician (purple) component and the rest.

2. The expansion inwards may correlate with Chalcolithic and Bronze Age processes, which seem to be way too important everywhere and also in Iberia. So I used the Bell Beaker map I copied from Harrison (see here) as cutoff for another mask (radius are relative to Bell Beaker density circles in the reference map):

If so the split between the Central (yellow) and East (orange) groups (to which the brown and red and other groups are closely affiliated) could be related to this Bell Beaker period and derived Bronze Age cultures. The yellow or Central component could originate in Los Millares (Almería province) and spread northwards to Ciempozuelos (Madrid province) and from there to other areas with the Cogotas I culture of the Bronze Age. 

The Purple (Western) component should be somehow related to Zambujal or Vila Nova de Sao Pedro (VNSP) culture of Portuguese Estremadura and spread northwards to tin-rich Galicia with the group of Montelavar already in the Bronze Age maybe.

The mysterious Red (Central-West) component could be related to some colonization of that area from the Bell Beaker dense area of Catalonia or the Denia district, or maybe even an older colonization, hard to say. What I know of that area in the late Prehistory is that it is ill-defined, partly for lack of research in the heavily farmed alluvial plain, and that it correlates with Southern Portugal but not fully, always showing a distinct personality, until it grows a clearly distinct personality in the Tartessian period, already in the Iron Age. It is also clear that the so-called Silver Road runs straight through that cluster and that it was important, and growingly so, in the Late Prehistory, having both commercial and religious significance and being clearly the main path of penetration of Phoenician influences inland, already in the proto-historical period. 

While still caught with feeble pins, this Silver Road speculative explanation seems to make much better sense than the Reconquista hypothesis the paper appears to spouse and which I see nonsensical because the patterns observed are not as we could expect. 

But of course it is always up to you to make up your own mind, I'm just offering some variant considerations that for me make some sense but that are by no means a well finished theory either, just better than the simplistic historical interpretation, which does not fit the facts too well.

Quickie: the pre-Indoeuropean evolution of ancient Iberians: from 'Sardinian' to 'Basque'

This may be needed as transition between the ancient Iberian genetic data of Valdiosera and Günther that I discussed two days ago and the modern Iberian genetic data that I'm planning to discuss very soon (just chewing on the data, because it is a bit perplexing in some aspects, but ref. Bycroft 2018 if you want to peek on it on your own). 

Fig. 1B from Valdiosera, Günther et al. 2018, annotated by me.

Just that: we see very clearly how ancient Iberians were at the beginning of Neolithic like modern Sardinians and by the time of Chalcolithic in some cases and at the Bronze Age everywhere, they had turned into something like modern Basques, i.e. more Paleoeuropean but not yet more Indoeuropean at all. 

Modern Spaniards/Iberians seem to be mostly that Basque-like Bronze Age base plus some Indoeuropean admixture from either the continent (Celts surely) or Italy (Romans no doubt). 

Maybe it is like stating the obvious but the obvious is not always obvious for everyone and understanding this will be handy when dealing with modern Iberian DNA and its structure.

Ancient DNA from the Balkans

This study has been for several months around but I have not discussed until now and is well worth a mention.

Ian Mathieson et al., The Genomic History Of Southeastern Europe. BioRXiv (pre-pub) 2017. doi:10.1101/135616

There is a lot of ancient autosomal DNA from the region but it basically says one thing: everything was almost exactly as expected from archaeology. The Karanovo-Gumelnita people, famed for inventing the Bronze Age a whole millenium earlier than anyone else, and nearby related cultures, were within the mainstream (Vasconic) Neolithic genetic grouping. This changed however with the kurgan invasion expressed primarily in the Ezero culture, which I've been told should be considered direct precursors of Thracians. But the change is not something radical: more genetic affinity with the steppe is visible than before and more generalized through all samples. 

Fig. 1-D - Supervised ADMIXTURE plot, modeling each ancient individual (one per row), as a mixture of
populations represented by clusters containing Anatolian Neolithic (grey), Yamnaya from Samara (yellow), EHG (pink) and WHG (green).  (click to expand)

Well, it is not exactly everything what is as expected, if we consider Polish Globular Amphorae culture, which I would have expected to be at least somewhat steppary, Indoeuropean, already but were not. Thus it seems I have to concede on this culture and its precursors being still part of the Vasconic Neolithic. This makes Indoeuropean penetration into Central-North Europe a much more sudden episode and one directly tied to Corded Ware culture and nothing else. It must have been perceived by its victims like a massive catastrophe, because it was a huge area which they conquered and to a large extent colonized in a very short span of time.

Lots of R1b in Epipaleolithic Balkans

Most interesting anyhow is the huge hoard of ancient Y-DNA R1b in the Iron Gates region (Lepenski Vir) before the Neolithic. This not only demonstrates, again, that this haplogroup is Paleoeuropean, at least in part, but, quite intriguingly makes earlier findings on modern data suggesting a possible origin or R1b-M269 in or near modern Serbia (Morelli 2010 and Myres 2010) at least somewhat plausible. However none of the Iron Gates R1b is described as R1b-M269 and in some cases it is excluded that it could be this sublineage. 

Thus the issue of the ultimate origins of this key lineage remains open, but let me underline that these Iron Gate individuals belonged to the WHG grouping, as did Villabruna (so far the oldest R1b carrier kown) and that they breach this way the assumed haplogroup homogeneity I2 conceived on merely Central and Northern European samples. Just as happened with mtDNA U haplogroup homogeneity when mtDNA H was detected by several independent studies of Iberian ancient DNA. It is normal to expect more diversity towards the south for several reasons but maybe the most critical of them is just average temperature, which makes the southern lands naturally more fertile (notably so for crops domesticated in the Middle East) and easier to inhabit. 

This trend was only broken in the Middle Ages when the heavy plough allowed the improved exploitation of deep Oceanic soils, being useless in the Mediterranean region of shallow soils however. It was only then when the center of European development moved from south to north, to Belgium specifically, where it remains till present day. So let's take Southern Europe a bit seriously, please.

Two big issues with Olalde 2018 (Indoeuropean Bell Beaker speculation)

"Just for being published in Nature it does not mean it is necessarily wrong" (popular saying).

Iñigo Olalde et al., The Beaker Phenomenon And The Genomic Transformation Of Northwest Europe. doi:10.1101/135962 (pre-pub version, no way I'm spending 1/3 of my monthly income on this, in case you're willing to waste your money, it's been recently published in Nature)

Issue 1: All comparisons are made between Anatolia Neolithic or other Early Neolithic in some cases and Yamna or Corded Ware.  Late Neolithic is not used nor, critically, is Hunter-Gatherer populations or anything related. 

This means that everything will be much more Yamna-like than it should, just because Yamna are 50% HG, while Early Neolithic are very low in this component. 

This is very apparent in the PCA:

It's junk-in: junk-out.

Issue 2: there is a huge sampling gap precisely where ancient mtDNA (and modern Y-DNA) tells us that the origin of the modern West-Central European genetics should be: in France and nearby areas like the Basque Country, West Germany. Sure: they sample some Eastern French sites but see "issue 1" above.

Nuff said.

Extensive ancient Iberian mtDNA analysis

A very interesting thesis on Iberian ancient mitochondrial DNA is available (found via Bell Beaker Blogger):

Christina Roth, Once upon a time in the West : paleogenetic analyses on Mesolithic to Early Bronze Age individuals from the Iberian Peninsula. University of Mainz (thesis), 2016. Freely available → LINK

As all theses, it is very extensive, and I can only make some comments here (space and time are always too limited, you know), hoping to grasp the most interesting aspects of it.

First of all Roth finds that Iberian hunter-gatherers (HGW in the paper) were not quite like Central European ones (HGC), at least not in the mtDNA. Instead, in this aspect the Central European hunter-gatherers were closer to Eastern European ones (HGE), as well as to the Pitted Ware late subneolithic population of Gotland.

Iberia-only mtDNA analysis

This will be a recurrent issue along the analysis she makes. But let's focus on Iberia by the moment. Notice that she does not just use her own data but also from many other sources, including some unpublished materials, this makes a bit difficult to follow all the details, so I feel I can only focus on the statistical analysis she makes and which is the core of the thesis.

Annotated by me, because I found the abbreviations quite hard to follow

The general overview is confirmed, with minor variations, in the cluster analysis (which I also took the liberty of annotating, but take my notes for what they are: mere scribbling on the margin in an attempt to better understand the data, nothing else):

Particular care not to take the arrows of my notes too seriously: they are just conceptual, a very loose sequencing of the available data for a very tentative visualization of it. If it helps you, cool, else ignore please.

In any case, it seems clear cluster 2 is more influenced by hunter-gatherer genetics and that, with the data available in this study, we reach the end of the timeline within it in the following regions: Upper Ebro and Basque Country (data up to Late Neolithic but see my own 2013 compilation for a longer period), Southern Iberia (up to Chalcolithic) Southeast and Northeast, this one after originally being in the "more Neolithic" cluster 1 (in fact the author does argue for Catalonia as main "gate" for Neolithic genetics into Iberia on light of the available data, which does not include another important "gate", the SE one, for lack of data for the early period).

Inversely, cluster 1 is more influenced by "farmer" genetics, first detected in the Northeast (Catalonia and nearby areas of Aragon) but then also affecting the Northern Plateau and the West (Central Portugal). This last is very important because it is here where a key civilizational hub, the oldest known civilization of the Atlantic shores, emerged in the Chalcolithic, playing a key role in the wider Megalithic and Bell Beaker phenomena. I have at times speculated that it might be the origin of "modernity" in Western European genetic pools but on light of this data I have to recant, the origin should be elsewhere, probably in/around what is now France (and therefore it's not likely to be directly related to Bell Beaker, except maybe in the islands, but rather to Michelsberg/SOM, Artenacian and such -- always in wait of more data, just a cautious hypothesis). 

Finally the farmer-leaning cluster reaches the Southern Plateau, near Madrid, what suggests a N→S move of the then-forming Cogotas I herder culture, rather than the opposite. 

What we do see is not inconsistent with modern Iberian genetics anyhow: while Central Europe seem to have seen an increase of "hunter-gatherer" genetics along time, in Iberia the main tendency is the opposite: an increase of "farmer" genetics and further dilution of the aboriginal genetic pool. There is however at least one clear exception in the Northeast and that is also consistent with modern Iberian genetics. Some regions (south, southeast and the totally unknown northwest) have only fragmentary sequences here, so unclear, although the final tendency, up to the Bronze Age, is to cluster 2b (i.e. mixed but rather tending to "hunter-gatherer" genetics).

To finish with the Iberia-only bloc, notice that these are the lineages found among early Iberian farmers by region (in color those haplogroups associated to the arrival of Neolithic per the available data):

Notice how the pool in the Northern region is quite modern-like, not yet exactly as it is locally today but it would pass quite unnoticed in a map of Europe.

Iberia and the rest of Europe

What about the pan-European context (with the usual huge blanks in France, Britain, etc.)? Quite interesting as well:

Annotated by Maju on fig. 23 (click to enlarge)

As mentioned before, the Iberian hunter gatherers (HGW) appear clearly distinct from their Central and Eastern cousins in the mtDNA analysis. And with all this Iberian dataset it becomes apparent that there seem to be two "zones of admixture": one for Iberians and another for Central Europeans, the difference being on which aborigines they mix with. 

Notice that it is not possible to differentiate here between local Central European and intrusive Eastern European admixture, as both aboriginal hunter-gatherer populations appear closely related in all analyses (maybe an artifact of the sampling strategy or maybe actually relevant, can't say). 

It also caught my eye that a German site (Blätterhöhle, Westfalia, famed because farmer and hunter-gatherers living side by side were located there some years ago), clusters intensely with Iberian hunter-gatherers and related populations. I have to research more on this matter (which I had ignored so far) but I suspect it may be very relevant, because we could get an even longer chain of early "modern" mtDNA pools, adding this site to Paternabidea (Navarre) and Gurgy (Burgundy), spanning a long stretch of Western Europe, an area quite neglected by archaeogenetics so far, it must be said.

It is also worth mentioning that UC (which I believe stands for Unetice Culture) pulls the "Central European zone of admixture" in the PCA downwards, with a polarity of its own, a polarity that should probably be considered as specifically Indoeuropean. 

The cluster analysis confirms much of what I just said above, not annotated for a change:

We see very clearly here a larger cluster more influenced by "farmer" genetics and a smaller one that includes all pre-Neolithic aborigines, plus two populations already post-Neolithic but clearly identifiable as at least largely aboriginal (PWC and BLA), plus a subcluster of Neolithic Iberians, from the North (NSE and EVN) and the West (CPE). 

The author notices that: Bernburg (BEC) and Funnel Beaker (FBC) samples (...) show almost no significant differences to any Iberian group, except to the Early Neolithic of Northern Spain (NSE) and Chalcolithic of East Spain (ESC). Hard to interpret but worth noticing, no doubt.

And there is a lot more in the thesis but I can only review so much, so take a look and tell me and the World if I'm missing something of relevance or you feel I'm misinterpreting something or whatever.

Mitochondrial DNA from post-Neolithic Santimamiñe (Basque Country)

Four human remains dated to the Bronze Age were sequenced for mitochondrial DNA in Santimamiñe cave (Kortezubi, Biscay, Basque Country), along with single instances from the Neolithic, Chalcolithic and Roman period.

J.C. López Quintana et al., NUEVOS DATOS SOBRE LA SECUENCIA DE USO SEPULCRAL DE LA CUEVA DE SANTIMAMIÑE (KORTEZUBI, BIZKAIA). Arqueología y Prehistoria del Interior Peninsular (ARPI), 2016. Freely accessible (PDF) → LINK [no DOI]

The mtDNA study is not "brand new" but a synthesis of a previous doctoral thesis and advance publications:

Un primer avance de este estudio fue publicado en la monografía de las campañas de 2004 a 2006 de Santimamiñe (Cardoso et al. 2011), incluyendo el conjunto completo en la Tesis Doctoral de L. Palencia Madrid (Palencia 2015).

So we are talking of relatively old data, that has partly remained within the (sometimes absurdly greedy and anti-social) academic circles until now. The relative antiquity of the DNA study is important when assessing it, because genetic analysis is evolving very fast and, in most cases in the rather closed and under-budgeted Spanish universitary circles, they tend to do things "the old way", so we are almost certainly dealing here with HVS-I sequencing, something that is not explicit in the paper (I'm searching for Leire Palencia's thesis to make sure but no luck until now). 

If I am correct in this (and I should be), then we must understand that it is impossible in many cases to determine the exact haplogroup in the crucial R0 upper tier haplogroup, which includes HV and the extremely common H. Lacking the original HVS-I sequences by the moment, I can't but take the authors labels at face value but I must warn here that where it reads "R0" it is almost certainly H (HV0 or V are easy to recognize with this method, as is R0a) and where it reads "H1" it is probably H1 but not 100% certain. 

For more details see the relevant PhyloTree page, where the HVS-I markers are the last bloc in blue, beginning always with the sequence "16" (the other markers in blue of lower numerical value are HVS-II, more rarely used, and the ones in black are the coding region markers, which are in this case fundamental for proper assignment).

The mtDNA haplogroups (as reported) are:

• Neolithic:
• U5a2a (S2011-M2, c. 5100 BCE)
• Chalcolithic:
•  T2b (S-1, c. 2000 BCE)
• Bronze Age:
• U5b (S2011-M1 c. 1700 BCE) 
• H1 (S2011-M4, c. 1700 BCE)
• R0 (S2011-M6, c. 1500 BCE)
• U3a (S2011-M3 c. 1300 BCE)
• Roman period: 
• R0 (S2011-M5, c. 300 CE)

Interpretation attempts

It's difficult to extract conclusions from them but they should be compared with other sequences from the area, for which I recommend my 2013 synthesis. In general, treat "R0" as meaning "H", even if I chose to use a different color (magenta instead of red) for exactitude. 

In order to aid that analysis, I reproduce here my 2013 graphic:

We cannot compare the single Neolithic and Roman Era individuals but we can compare the Satimamiñe Chalcolithic+Bronze group of five sequences with the peripheral Chalcolithic large dataset of De La Rúa:

1. R*+H (very similar):
1. Peripheral "Basque" Chalcolithic: ~40%
2. Santimamiñe Chalcolithic+Bronze: 40% 
3. Santimamiñe Bronze only: 50%
2. U(xK) (very different):
1. Peripheral "Basque" Chalcolithic: ~15%
2. Santimamiñe Chalcolithic+Bronze: 40%
3. Santimamiñe Bronze only: 50%
3. Other lineages (all them of certain Neolithic immigrant origin, very different too):
1. Peripheral "Basque" Chalcolithic: ~45%
2. Santimamiñe Chalcolithic+Bronze: 20%
3. Santimamiñe Bronze only: 0%

However one of the U(xK) lineages in Santimamiñe is U3, which is also quite certain to be of Neolithic immigrant origin, and one is an important figure when n=5 so we can also see it this way:

1. Paleolithic lineages:
1. Peripheral "Basque" Chalcolithic: ~55%
2. Santimamiñe Chalcolithic+Bronze: 60%
3. Santimamiñe Bronze only: 75%
2. Neolithic lineages:
1. Peripheral "Basque" Chalcolithic:  ~45%
2. Santimamiñe Chalcolithic+Bronze: 40%
3. Santimamiñe Bronze only: 25%

The comparison of #1 with #2 is much more similar. This could be important, because Santimamiñe is not anymore a "peripheral" site, as are those from De La Rúa's dataset, but a rather central one with a extremely long and uninterrupted Paleolithic sequence, dating to Neanderthal-made Chatelperronian culture. It is still a single site with a small number of samples but it does provide a counterpoint that, in one approach could produce similar results. 

But, surprisingly, when we consider a distinct Bronze Age category, comparing not anymore with #2 but with #3 everything changes, suggesting a totally different interpretation of the available dataset, in which, the "Chalcolithic interlude" (if real at all, more data is needed) would be reversed quickly with the onset of the Bronze Age. 

I am sorry but I cannot lean for either interpretation: the data is just not extensive enough to allow for conclusions. I am tempted to support the continuity hypothesis, allowing only for lesser changes to happen, and keep the Chalcolithic dataset under a big question mark, but the question mark is admittedly a bit smaller now: something in terms demographic may have happened in the Chalcolithic period and may have been reversed in the Bronze Age. But "may" is not "for sure", we need more data points.

Feel free to discuss in good mood, as always.

Thanks for the heads up to Jean Lohizun (again).

All the Neolithic and Chalcolithic of Ireland in a single paper

This entry should be a "quickie" because I wouldn't even know where to begin in order to analyze this comprehensive synthesis and not at all because it is a lesser study, all the oposite. Just to say that the average reader of this blog will want to read it, much more if they are Irish.

However I think that the paper raises some interesting questions regarding the chronology of "modern genetic Irishness" and the arrival of the Y-DNA lineage R1b to the island, which I cast below for your insights.

T. Rowan McLaughling et al., The Changing Face of Neolithic and Bronze Age Ireland: A Big Data Approach to the Settlement and Burial Records. Journal of World Prehistory 2016. Open access → LINK [doi:10.1007/s10963-016-9093-0]

Abstract

This paper synthesizes and discusses the spatial and temporal patterns of archaeological sites in Ireland, spanning the Neolithic period and the Bronze Age transition (4300–1900 cal BC), in order to explore the timing and implications of the main changes that occurred in the archaeological record of that period. Large amounts of new data are sourced from unpublished developer-led excavations and combined with national archives, published excavations and online databases. Bayesian radiocarbon models and context- and sample-sensitive summed radiocarbon probabilities are used to examine the dataset. The study captures the scale and timing of the initial expansion of Early Neolithic settlement and the ensuing attenuation of all such activity—an apparent boom-and-bust cycle. The Late Neolithic and Chalcolithic periods are characterised by a resurgence and diversification of activity. Contextualisation and spatial analysis of radiocarbon data reveals finer-scale patterning than is usually possible with summed-probability approaches: the boom-and-bust models of prehistoric populations may, in fact, be a misinterpretation of more subtle demographic changes occurring at the same time as cultural change and attendant differences in the archaeological record.

The study should be very useful to anyone trying to understand the prehistory of Ireland, not the least because of its many maps and this extremely cool sequential maps video from pre-Neolithic times (5th millennium BCE) to the gates of the Bronze Age (early 2nd millennium BCE). Notice that in the Isles they tend to call "Bronze Age" to the Chalcolithic (Copper and Stone Age) and hence the title, which is a bit misleading.

An example of the very cool and highly informative maps and data you'll find in this study:

Fig. 3 - Map of Ireland showing Early Neolithic sites

 

Depopulation and resettlement? When?

An intriguing issue is the boom and bust cycles, particularly the almost total absence of signs of human activity around the end of the 4th millennium (3300-3000), suggesting maybe a depopulation after the first farmer colonization (?). There are clear booms around 4000, 3700, 3500, 2900, 2500 and since 2200 (Bell Beaker era). All this is something to chew about.

Particularly I'd raise the following question here: we know that a woman from c. 3400-3100 BCE (just at the depopulation gap?) was a typical Neolithic European, most similar to SE Spaniards and Sardinians, and that a man from c. 2200-1500 (Bell Beaker boom) was virtually identical to modern Irish and "British Celts" like Scots, Welsh and Cornish, carrying the common and controversial R1b patrilineage. 

The initial reading many of us made was that these new genetics may have arrived with Bell Beaker and that maybe Bell Beaker was more influential in terms demographic than we used to think, at least in Ireland. However, with this archaeological sequence on hand it seems at least reasonable to think that the major resettlement of an almost deserted Ireland happened after 3000 BCE but significantly earlier than the Bell Beaker phenomenon, which only reaches Northern Europe (Ireland included) c. 1500 BCE. What's your opinion?

Ancient mtDNA from a Megalithic tomb near Atapuerca

A new study has produced 22 mitochondrial sequences from a Megalithic tomb (dolmen) in Alto del Reinoso, some 7 Km NE of Atapuerca.

Kurt W. Alt, Stephanie Zech et al., A Community in Life and Death: The Late Neolithic Megalithic Tomb at Alto de Reinoso (Burgos, Spain). PLoS ONE 2016. Open access → LINK [doi:10.1371/journal.pone.0146176]

Abstract

The analysis of the human remains from the megalithic tomb at Alto de Reinoso represents the widest integrative study of a Neolithic collective burial in Spain. Combining archaeology, osteology, molecular genetics and stable isotope analysis (87Sr/86Sr, δ15N, δ13C) it provides a wealth of information on the minimum number of individuals, age, sex, body height, pathologies, mitochondrial DNA profiles, kinship relations, mobility, and diet. The grave was in use for approximately one hundred years around 3700 cal BC, thus dating from the Late Neolithic of the Iberian chronology. At the bottom of the collective tomb, six complete and six partial skeletons lay in anatomically correct positions. Above them, further bodies represented a subsequent and different use of the tomb, with almost all of the skeletons exhibiting signs of manipulation such as missing skeletal parts, especially skulls. The megalithic monument comprised at least 47 individuals, including males, females, and subadults, although children aged 0–6 years were underrepresented. The skeletal remains exhibited a moderate number of pathologies, such as degenerative joint diseases, healed fractures, cranial trauma, and a low intensity of caries. The mitochondrial DNA profiles revealed a pattern pointing to a closely related local community with matrilineal kinship patterns. In some cases adjacent individuals in the bottom layer showed familial relationships. According to their strontium isotope ratios, only a few individuals were likely to have spent their early childhood in a different geological environment, whilst the majority of individuals grew up locally. Carbon and nitrogen isotope analysis, which was undertaken to reconstruct the dietary habits, indicated that this was a homogeneous group with egalitarian access to food. Cereals and small ruminants were the principal sources of nutrition. These data fit in well with a lifestyle typical of sedentary farming populations in the Spanish Meseta during this period of the Neolithic.

While the nutritional part has some interest, it is ultimately not too conclusive (high protein diet, similar to that of Dordogne Neolithic, high incidence of caries, three individuals who may have been raised outside the "closely knit" community), so I will focus my attention on the mitochondrial lineages.

These are:

• U5b - 2
• U5b2b3 - 4
• U5b3 - 1*
• U4 - 1*
• V - 2
• K - 4
• K1a - 1
• K1a1 - 3
• X - 3
• T2b - 3
• T2a1b - 1*
• H3 - 1
• J - 1

The three individuals marked with an asterisk (*) might have been raised in other villages, two of them are adult men and the third one a teen-ager of unknown gender. While the possible immigration of men could suggest matrilocality, the reality is that most individuals buried whose gender could be discerned are men anyhow, and all the rest seem to share the same kind of diet (i.e. probably raised in the Alto del Reinoso community), so most unclear.

Notice also that, because of the limitations in haplogroup identification in ancient DNA, apparent "upstream" lineages such as U5b or K can perfectly be the same as "downstream" ones like U5b2b3 or K1a1 respectively. We just do not know for sure.

My preliminary diagnostic was that it looks a quite typical "mixed Neolithic" pool, much like the one of El Portalón in nearby Atapuerca, with dominance of "Neolithic" lineages (K, X, T, J - maybe also V and H3, not yet detected in Western hunter-gatherers) but also a high frequency of "Paleolithic" ones of the U typology (U5 and U4). It is almost absolutely "pre-modern", lacking the high frequencies (40-60%) of mtDNA H found today (and also found in the Neolithic of Paternabidea and Gurgy, in Navarre and Burgundy respectively) and therefore having great excess of both "Neolithic" and U frequencies.

It must be said that Northern Burgos is even today quite low in mtDNA H, with only 33% of this widespread lineage (half of it H3), being also unusually high (30%) in haplogroup U frequencies (ref.), but in any case the mtDNA pool is at the very least not standard for the wider geography and must have experienced some changes in the meantime therefore.

For that reason I considered comparing with the other nearby sites within this small Atapuerca-La Brújula mountain gates area that divides the Duero from the Ebro basins. The result (in percentages) is as follows:

Site	date (BCE)	n	U5	U4	H*	H1	H3	V	J	T2	X	K	U3
Reinoso	~3700	22	27	5	-	-	5	9	5	18	14	18	-
Portalón	~3000	7	29	-	-	-	29	-	14	-	14	14	-
Mirador	~2500	20	-	-	5	20	-	-	10	20	20	20	5

[Ref. links for El Portalón and El Mirador (both in Atapuerca)].


The three sites provide jointly a most interesting sequence for the district. I would say that Reinoso and Portalón seem quite similar, especially considering that the latter sample is very small, allowing for some random fluctuations (decrease in V and T2, increase in H3 and J). However in El Mirador, some 500 years later, we just cannot ignore that there are notable changes.

While the main "Neolithic" lineages (J, T, X, K) remain pretty much the same, all the rest is completely different: U5 (and its faithful sidekick U4) has vanished, has happens with H3 and V, instead we see a sudden outburst of H1 (and H*) and also the less impressive appearance of U3.

What does this mean? Let's go back to the modern mtDNA pool in Northern Burgos Province (n=24) as per Behar 2012:

• H1: 2 (8%)
• H3: 4 (17%)
• U: 8 (33%)
• K: 2 (8%)
• T: 2 (8%)
• J: 2 (8%)
• Singletons: H*, H4, V, L2

It seems to me that those ancient genetic pools are still very present: although there are greater frequencies of H and U than the average produced by merely admixing Reinoso and Mirador, the underlying typology that we can discern (within H most clearly) seems to conform to what those ancient populations already had. Instead the "Neolithic" lineages are less common.

Why?

My guess is that these ancient sites lay all in a key passage of a most strategic route, Spain's National Road 1, St. James' Way, Roman road Ab Asturica Burdigalam and surely much older trade and cultural routes went through that series of mountain passes. This may have attracted more immigrants from the Neolithic settler populations from the Mediterranean, who may have been surrounded by others of more "aboriginal" roots (mostly Paleolithic ascendancy) and rather low visibility for archaeologists.

It remains to be confirmed if Bell Beaker (associated with El Mirador site) may be directly blamed for the introduction of mtDNA H1 in the district. It is indeed possible but in any case the long term impact was limited.

It must also be understood that all this has very little to no relationship with what may have happened in the Basque Country, in spite of being not far away: the genetics involved, both ancient and modern, are quite different. It may be surprising how much the genetic pool can vary in just 200 Km but the rugged geography and diverse ecology seem to favor this kind of sharp distinctions. And, regardless of the causes and the surprise, it may cause, the data is there and is very clear.

Irish ancient DNA

This study was published just a few days ago but is already from the previous year, tricks of the calendar. It is a scheme-breaker in several aspects, so I hope to be able to reflect here the most important aspects of it.

Lara M. Cassidy, Rui Martiniano et al., Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome. PNAS 2015. Freely accessible → LINK [doi: 10.1073/pnas.1518445113]

Abstract

The Neolithic and Bronze Age transitions were profound cultural shifts catalyzed in parts of Europe by migrations, first of early farmers from the Near East and then Bronze Age herders from the Pontic Steppe. However, a decades-long, unresolved controversy is whether population change or cultural adoption occurred at the Atlantic edge, within the British Isles. We address this issue by using the first whole genome data from prehistoric Irish individuals. A Neolithic woman (3343–3020 cal BC) from a megalithic burial (10.3× coverage) possessed a genome of predominantly Near Eastern origin. She had some hunter–gatherer ancestry but belonged to a population of large effective size, suggesting a substantial influx of early farmers to the island. Three Bronze Age individuals from Rathlin Island (2026–1534 cal BC), including one high coverage (10.5×) genome, showed substantial Steppe genetic heritage indicating that the European population upheavals of the third millennium manifested all of the way from southern Siberia to the western ocean. This turnover invites the possibility of accompanying introduction of Indo-European, perhaps early Celtic, language. Irish Bronze Age haplotypic similarity is strongest within modern Irish, Scottish, and Welsh populations, and several important genetic variants that today show maximal or very high frequencies in Ireland appear at this horizon. These include those coding for lactase persistence, blue eye color, Y chromosome R1b haplotypes, and the hemochromatosis C282Y allele; to our knowledge, the first detection of a known Mendelian disease variant in prehistory. These findings together suggest the establishment of central attributes of the Irish genome 4,000 y ago.

The two sample sites are from North Ireland, being the so-called Neolithic one from the interior (Co. Down, c. 3200 BCE) and the so-called Bronze Age ones are from a small island (Rathlin) north of the main island (Rathlin 1 and 2 from c. 1900 BCE, Rathlin 3 from c. 1600 BCE). 

I say "so-called" because I'm not really confident that the terms "Neolithic" and "Bronze Age" apply in fact to most of them (I'd rather use Chalcolithic, shorthand for "advanced Neolithic with social complexity, regardless of metals", for all but Rathlin 3). I think in any case that the divider here is not metallurgy as such but actually the Bell Beaker divide: before and after Bell Beaker.

Bell Beaker is becoming a key element to our understanding of the demographic changes in Northern Europe, more than I would have expected admittedly. In the case of Ireland (and to a lesser extent parts of Britain) the arrival of the Bell Beaker phenomenon is accompanied with striking demographic growth, which may (or not) imply new settlement from outside. For Ireland, it seems growingly clear now, it probably does, unless Rathlin is a very unusual site, what is not parsimonious as we will see. 

Enough with the intro, let's get to the substance.

 

Haploid genetics

Ballanyhatty (Co. Down), a woman, carried the mitochondrial haplogroup (matrilineage) HV0. Rathlin 1 carried U5a1b1e, Rathlin 2 U5b2a2 and Rathlin 3 carried J2b1a. The only thing remarkable here is the lack of haplogroup H, the most common one in Europe today and detected since the Magdalenian era in Iberia, but more commonly later on within Neolithic. It can be a fluke of course but the shallow impression is that the mtDNA pool is "pre-modern". However all the rest is very "modern" in Rathlin Island, so... let's assume it's a mere fluke.

The three Rathlin individuals are all men, and their Y-DNA haplogroup has been successfully sequenced: they all belong to R1b-M529, the most common patrilineage in Ireland (and much of Britain and also Brittany) to this day. There's some hints that some of them could belong to downstream subhaplogroups but, if you read the fine print (the supp. materials) this is quite unclear, so let's leave it at this. 

R1b-S116 structure per Valverde 2015

The implications of this data point are important: it clearly defines a terminus ante quem for all possible R1b-M529 and upstream haplogroups' chronologies. Whoever defended a shorter chronology was clearly wrong. Together with a German Bell Beaker individual, these are the oldest R1b-S116 known so far, what is hardly surprising considering the huge blank in aDNA sampling in Western Europe but also suggests that, at least in some areas, Bell Beaker was implicated in the expansion of this most important European patrilineage and in general in the formation of modern-like Western European populations.

There are many open questions here yet because we lack ancient DNA data from France, West Germany, Belgium, Britain, much of Iberia, etcetera. But, with these new data points, I am beginning to believe that Bell Beaker was, if not a general cause, at least a key pivot around which these demographic changes leading to modern populations took place. It was probably a cause in Ireland but it's truly hard to extrapolate to other regions, where aDNA information is missing and archaeological one suggests different patterns of change or continuity. 

Autosomal DNA

The most striking implication of the autosomal DNA of these two Irish sites is that Rathlin men are almost identical to modern Irish (also Scots, Welsh and Cornish), while the much older Ballanyhatty woman is only slightly similar to modern Irish (and Scots), being much more like Sardinians and some South Iberians (what is congruent with what happens to all other Neolithic samples through much of Europe). 

Selection from fig. 3

So we are before a clear-cut demographic change in Ireland (and maybe other regions) at some point in the third millennium BCE. The most plausible date for the beginning of this change is probably around 2500 BCE, when we see the start of significant demographic growth in Ireland and is also the approx. date for Bell Beaker arrival to the island and other parts of Northern Europe (several centuries older in the South however).

Putting these samples in the wider context the authors get this:

Fig. 1. Genetic affinities of ancient Irish individuals. (A and B) Genotypes from 82 ancient samples are projected onto the first two principal components defined by a set of 354,212 SNPs from Eurasian populations in the Human Origins dataset (29) (SI Appendix, Section S9.1 and S10). (A) This PCA projects ancient Eurasian Hunter–Gatherers and Neolithic Farmers, where they separate clearly into Early Neolithic, MN (including the Irish Ballynahatty genome), and several hunter–gatherer groups. (B) PCA projection of Late Neolithic, Copper, and Bronze Age individuals where the three Rathlin genomes adopt a central position within a large clustering of European Bronze Age individuals. (C) A plot of ADMIXTURE ancestry components (K = 11) of these same ancient genomes. In West and Central Europe, ancient individuals are composed almost entirely of two dominant strands of ancestry, linked to hunter–gatherer (red) and early farmer (orange) populations, until the Late Neolithic. At this point, a third (green) Caucasus component features. Previously, this component was only seen in ancient Steppe and Siberian populations such as the Yamnaya. The three Rathlin genomes each display this Caucasus strand of ancestry whereas the Irish Neolithic does not.

Sure: a key element here is the "teal" Caucasus-related component, which is a tell-tale signature of the Indoeuropean or Kurgan expansion into Europe. As exercise to get a rough estimate of how much Indoeuropean (Yamna-like) ancestry there is in each sample, I propose you to get a ruler and a calculator, measure it for each sample and find the resulting fraction. You can also do the same for the early Neolithic (EEF) ancestry, using the "orange" component. There is an interesting substantial leftover fraction that can only be extra "hunter-gatherer" (HG), wherever it comes from. 

My own estimates are as follows:

• Late Neolithic (LN) samples: 80% EEF + 20% extra HG.
• German LN (early Kurgans) = 23% IE + 40% EEF + 37% HG → 27% extra HG relative to LN
• Corded Ware = 64% IE + 21% EEF + 15 HG → 10% extra HG rel. to LN
• Elbe Bell Beaker (avg.) = 13% IE + 44% EEF + 43% HG} → 32% extra HG rel. to LN
• Irish BA = 25% IE + 34% EEF + 41% HG} → 32% extra HG rel. to LN

There is some data in the supp. materials (S12.2.2) which is roughly consistent with this, although their fraction of extra HG (using Lochsbour as reference) is smaller than mine, while their Yamna or IE one is larger instead (no idea why this lesser contradiction, honestly, although they almost overlap once we include error margins). 

Where does this extra HG fraction comes from? It is quite apparent that the currently available samples do not include its source. As I have mentioned many times, there is a huge "Atlantic" blank in the autosomal samples, including nearly all France and many areas around it: Switzerland, West Germany, Low Countries, Britain and about 3/4 of the Iberian Peninsula. 

In this study however we get a hint in the supp. materials: KO1, an Epi-Magdalenian sample from Hungary, stands out like a sore thumb in the f3 analyses of all three Rathlin samples:

Figure S12.1. Outgroup f3-Statistics for each ancient Irish Individual. Tests in the form f3(Mbuti; IA, X), where IA is an Irish ancient genome and X is any other ancient individual or population. Data points are coloured by archaeological context.

Obviously the origin of the extra HG cannot be KO1 as such but there must be one or several populations, as of yet unsampled, in which this extra HG (most akin to KO1) was notorious. My best candidates as of now are the following cultures:

• Michelsberg, which replaced LBK in most of Germany, North France, Belgium, Switzerland, etc. prior to the Corded Ware shockwave. It's part of the wider Funnelbeaker and Megalithic phenomena and one of the ancient cultures I really want to see sampled in some depth. 
• Artenac, which replaced previous layers in all West France and Belgium and is part of the wider Megalithic and Bell Beaker phenomena. It originated around Dordogne and is usually considered proto-Aquitanian, i.e. proto-Basque.
• The major civilization of Zambujal or Vila Nova de Sao Pedro in Portuguese Estremadura, which was a key pivot in the Megalithic and particularly the Bell Beaker phenomenon.

And in general I'd complement these with samples from all the Atlantic facade of Europe, including Britain, the Basque Country (a lot was going on in the Chalcolithic here in spite of the small size), West France, Belgium, the Rhône valley and Switzerland, etc. If we'd have data points for all these areas in the Chalcolithic period, we'd surely have a much more clear picture of what was going on in Europe in this critical period of demographic change. Definitely it's not just Corded Ware and the Elbe basin can only give us so much information anyhow. 

This is also important regarding the origins and spread of R1b-S116 and its "brother" haplogroup U106, no kidding. Let's sample the West, it's about time.

Neolithic genomes from Northwestern Turkey

Or yet another ancient European DNA study, with some quirks and, critically, the first ancient farmer sample from the Eastern Mediterranean, specifically Northwestern Anatolia, near Yenişehir (Bursa province).

Iain Mathieson et al. Eight thousand years of natural selection in Europe. BioRxiv (pre-pub), 2015. Freely accessible → LINK [doi: http://dx.doi.org/10.1101/016477]

Abstract

The arrival of farming in Europe around 8,500 years ago necessitated adaptation to new environments, pathogens, diets, and social organizations. While indirect evidence of adaptation can be detected in patterns of genetic variation in present-day people, ancient DNA makes it possible to witness selection directly by analyzing samples from populations before, during and after adaptation events. Here we report the first genome-wide scan for selection using ancient DNA, capitalizing on the largest genome-wide dataset yet assembled: 230 West Eurasians dating to between 6500 and 1000 BCE, including 163 with newly reported data. The new samples include the first genome-wide data from the Anatolian Neolithic culture, who we show were members of the population that was the source of Europe's first farmers, and whose genetic material we extracted by focusing on the DNA-rich petrous bone. We identify genome-wide significant signatures of selection at loci associated with diet, pigmentation and immunity, and two independent episodes of selection on height.

As you can see from the title and the abstract, much of the study is focused on more or less debatable selection signatures. Interesting, of course, but not what my greatest interest, less so as I perceive that there is missing data that may be crucial for the understanding of some of such selection, notably the mainstream European LCT 13910-T allele.

How can you do an analysis of selection on this allele while ignoring the first known carriers of it: Chalcolithic (proto-)Basques and Swedes (Gökhem particularly)?

Luckily there are other highlights...

Northwestern Anatolian ancient genetics

The new ancient Neolithic samples come from two sites: Menteşe Höyük (n=5) and Barcın Höyük (n=21), both located in the Yenişehir plain, southeast of Istanbul across the Marmara Sea. The archaeological context of the samples, as well as that of many other European ones, resequenced for this study with new technology, is discussed in the Supplementary Information section.

These ancient Northwest Anatolian farmers have shown to be very similar to early European farmers. The authors estimate that these were only some 10% admixed with Paleoeuropeans, relative to the Anatolian samples, although later individuals from the West did of course had further Paleoeuropean admixture.

I must emphasize the adjective "Northwestern" because Anatolia Peninsula is a large territory where the Neolithic had differential implementation in time and cultures. Critically we cannot be certain that there is any identity between these Western Anatolian first farmers and those from South-Central Anatolia, for example those of the world-famous Çatal Höyük village. This is because the Neolithic of South-Central Anatolia is much older and there are archaeological indications that suggest that the settlement of Western Anatolia and Greece took place via coastal migration. The origin of this coastal migration probably involved Cyprus, which in turn was more directly related to the Neolithic of the Levant (PPNB) than to that of South-Central Anatolia. Some genetic data also seem to suggest that the precursors of early European farmers were from the Levant, rather than from further North. But of course the full resolution of this mystery will have to await for ancient DNA from the relevant regions, something that may be aided by the recent technological breakthroughs but that will also require peace, so geneticists and archaeologists can do their field work (there are of course many other much more excruciating reasons to hope for peace and normalization in West Asia, naturally, don't get me wrong).

In any case we finally have a reference genome for what can be termed the Aegean Neolithic and it seems it was even closer to European derivatives. We cannot anyhow discard that there was some backflow from Greece or other parts of the Balcans to Western Anatolia because there was indeed some interaction across the Aegean. However a much more clear cut cultural divide has been argued to exist between the cultures of the Marmara Sea and those of inland Thrace, so, if there was any such backflow, it probably happened before the expansion of Thessalian Neolithic northwards.

Principal Component Analysis

This is the Principal Component Analysis provided by this study (fig. 1B). The modern samples are in gray with no labeling whatsoever but I guess most readers will approximately identify them easily, as the basic layout has been repeated in so many recent aDNA studies:

Figure 1: Population relationships of samples. (...) B: Principal component analysis of 777 modern West Eurasian samples (grey), with 221 ancient samples projected onto the first two principal component axes and labeled by culture. Abbreviations: [E/M/L]N Early/Middle/Late Neolithic, LBK Linearbandkeramik, [E/W]HG Eastern/Western hunter-gatherer, [E]BA [Early] Bronze Age, IA Iron Age.

As in Olalde 2015 or Haak 2015, or even Lazaridis 2014, WHGs appear located rather "towards the South", unlike in some other PCAs, particularly Europe-only ones. I do find this to be interesting and potentially informative, at least while we await for Atlantic European ancient nuclear DNA.

Therefore, you'll forgive me for the redundancy of reusing the above image a couple of times in order to make a couple of points.

The thesis that most of these studies are pushing for is a simplistic triangular scenario for the formation of modern Europeans with a formula that can be described as {x.EEF+y.WHG+z.Kurgan}. I don't deny that this is quite approximative but I am also quite certain that it is missing important clues. In fact, the triangular thesis seems to fail to explain most Northern European genetic makeup, while the origins of Basques also remain somewhat unexplained by it. Let's see:

Annotations on the PCA: triangular thesis fails, extra HG (EHG?) is needed.

It would seem quite apparent that the triangular thesis (described on the PCA by a slashed line) fails to explain most of Western and Northern European genetic makeup, which is clearly much more deviated towards Paleoeuropean hunter-gatherers than it allows.

Just including on the equation Eastern European hunter-gatherers (dotted line) would be enough to solve most of the problem, although it does of course arises other questions about how and when this extra Paleoeuropean blood was incorporated.

This solution would still leave Basques outside of it. It requires instead of a Western hunter-gatherer extra admixture on top of a simple Neolithic cluster basis:

Annotations on the PCA: Basques can be explained (?) as simple {Neo-European + WHG admixture}

Of course that the actual sources of Paleoeuropean admixture can be more complex, as suggested by some studies, like Günther & Valdiosera 2015, who claimed Scandinavian HG admixture not just in Gökhem farmers but also in Ötzi ("Iceman" in the above graph). These did not use EHG samples but in any case, if correct, it is a pre-Kurgan admixture from the Northeast of the subcontinent.

A key excerpt from the Supplementary Information 2 section that someone (Simon, I think) used to argue for steppe ancestry in Basques in a discussion at Eurogenes blog:

The Iberian Chalcolithic population lacks steppe ancestry, but Late Neolithic central and northern Europeans have substantial such ancestry (Extended Data Fig. 3E) suggesting that the spread of ANE/steppe ancestry did not occur simultaneously across Europe. All presentday Europeans have less steppe ancestry than the Corded Ware5, suggesting that this ancestry was diluted as the earliest descendants of the steppe migrants admixed with local populations. However, the statistic f4(Basque, Iberia_Chalcolithic; Yamnaya_Samara,Chimp)=0.00168 is significantly positive (Z=8.1), as is the statistic f4(Spanish, Iberia_Chalcolithic; Yamnaya_Samara, Chimp)=0.00092 (Z=4.6). This indicates that steppe ancestry occurs in present-day southwestern European populations, and that even the Basques cannot be considered as mixtures of early farmers and hunter-gatherers without it4.

What does this say in fact? It says nothing about Western Hunter-Gatherers, only that Basques appear as more Yamna-like than the Iberian Chalcolithic sample. I see no reason why this cannot be caused by simple extra WHG admixture, although it can also imply other Paleoeuropean such as SHG or EHG inflow. What I do see from other studies (and again for all I can discern in this one) is that Basques do lack any clear Yamna signature and notably their Caucasus or Northern West Asian component (always present where Kurgan admixture is unmistakable and therefore a clear indicator of it) is effectively zero (some individuals may have tiny non-zero such component, all very normal).

Admixture analysis with two and three source populations

The authors find that, while many populations can be modeled as product of simple two-way admixture, many need a three-way model, notably from the late Chalcolithic onwards:

Extended Data Figure 2: Early isolation and later admixture between farmers and steppe populations. A [actually B]: Mainland European populations later than 3000 BCE are better modeled with steppe ancestry as a 3rd ancestral population. B [actually A]: Later (post-Poltavka) steppe populations are better modeled with Anatolian Neolithic as a 3rd ancestral population. C: Estimated mixture proportions of mainland European populations without steppe ancestry. D: Estimated mixture proportions of Eurasian steppe populations without Anatolian Neolithic ancestry. E: Estimated mixture proportions of later populations with both steppe and Anatolian Neolithic ancestry. [F is below]

However this varies, because notably the Iberian Chalcolithic sample can still be modeled as a two-way admixture, what is in conformity with the consideration that the increase in the complexity took place not in any single event but rather first in Central and Eastern Europe and only later further West. This is in full conformity with the Kurgan model of Indoeuropean expansion, although it may require some refinement here and there.

For example it is becoming quite obvious that there was not only a westward movement of Eastern European populations but also a subsequent eastward backflow of the resulting admixed Central European ones. This is discussed in the supplementary materials, from page 43 onwards.

Extended Data Figure 2: (...) F: ADMIXTURE plot at k=17 showing population differences over time and space.
(click to expand)

To this I must add my conviction that the triangular model is not enough to actually explain modern European genetics and that greater Paleoeuropean genetic input in Northern and Western Europe is required as well. The great challenge in this regard is to sample Atlantic (and Baltic) Europe properly and extract whatever consequences that ancient genomes from these areas may provide. 

Naturally there is also some other research to be done in West Asia, where a good deal of the European (and also West Asian, naturally) ancestors lived once upon a time. That is the other major challenge. In this sense this study must be commended for its breakthrough in sampling ancient Northwestern Anatolians, which is a step in the right direction.

There are other blank zones to be researched as well in Southern Europe (Italy, Balcans) that may well provide complementary information.

Alleged selection

The authors claim to have found evidence for selection in twelve different alleles. I remain mildly skeptic because it is hard to judge if this was all selection or founder effect was involved as well. 

Some of the alleged targets of selection are:

Lactase persistance: rs4988235, also known as 13910-T, already mentioned above. The authors mention that the allele’s earliest appearance in our data is in a central European Bell Beaker sample (individual I0112) that lived between approximately 2300 and 2200 BCE. Older signals from the Chalcolithic Basque Country (fixated in a subpopulation) and Sweden are totally ignored. Of course it is a draft so far but it is clear that key information, widely available, is being ignored.

A light skin allele known as rs16891982 (in the gene SLC45A2). This allele was low in the studied ancient populations (but again might have been higher in the blank under-researched areas, I can't say). Unlike it, the derived allele of gene SLC24A5, was fixated in Neolithic NW Anatolians, as well as derived European ancient populations, being a clear case of founder effect (although it may have also helped with adaption to the low vitamin D diet caused by transition to agriculture). There are other pigmentation genes that may have been selected in complex interaction, as they seem to be partly correlated with latitude and are hard to explain based on ancient populations alone.

An important datum here is that: unlike closely related western hunter-gatherers, the Motala samples have predominantly derived pigmentation alleles at SLC45A2 and SLC24A5. So... is there another source of these light skin alleles (there are others and much is unknown anyhow) that is not from Neolithic farmers?

Another selection target is in the TLR1-TLR6-TLR10 gene cluster, which seems related to resistance to mycobacteria such as those causing leprosy, tuberculosis, etc. Regarding this complex cluster, I rather quote:

The strongest signal is at rs2269424 near the genes PPT2 and EGFL8 but there are at least six other apparently independent signals in the MHC (Extended Data Fig. 3); and the entire region is significantly more associated than the genome-wide average (residual inflation of 2.07 in the region on chromosome 6 between 29-34 Mb after genome-wide genomic control correction). This could be the result of multiple sweeps, balancing selection, or background selection in this gene-rich region.

The EDAR gene, related to tooth morphology (remember Pippi?) and hair thickness, as well denser sweat and mammary glands, in East Asians is also listed. Curiously enough, half of the Motala individuals (Epipaleolithic Sweden), carried the derived allele of rs3827760. Modern Scandinavians often have this derived allele, although the authors believe that it is because of more recent admixture:

The EDAR derived allele is largely absent in present-day Europe except in Scandinavia, plausibly due to Siberian movements into the region millennia after the date of the Motala samples.

Uh, really? How can you be so sure? I am very skeptic here again and would rather suspect a more complex pattern of partial Paleolithic (or at least Epipaleolithic) continuity, which may indeed have been brought from East Asia with the proto-Uralic migrations (or whatever). 

Another trait for which the authors claim selection is what they call "genetic height", i.e. height not measured from the actual individuals but from alleles that are believed to influence it. They argue for selection for lower height in Neolithic and Chalcolithic Iberia and for greater height in the Steppe instead, both being corrected to greater height in modern populations. Without objective measures to control for the assumed "genetic height", among other reasons, I find the whole story a bit hard to believe but who knows?

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