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Category Archives: autosomal DNA

Ancient DNA from Clovis culture is Native American (also Tianyuan affinity mystery)

Figure 4 | [c] (…) maximum likelihood tree. 
A recent study on the ancient DNA of human remains from Anzick (Montana, USA), dated to c. 12,500 calBP, confirms close ties to modern Native Americans, definitely discarding the far-fetched and outlandishly Eurocentric “Solutrean hypothesis” for the origins of Clovis culture (what pleases me greatly, I must admit).
While this fits well with the expectations (at least mine), there is some hidden data that has surprised me quite a bit: it sits at the bottom of a non-discussed formal test graph in which modern populations are compared with both Anzick and Tianyuan (c. 40,000 BP, North China). See below.
Morten Rasmussen et al., The genome of a Late Pleistocene human from a Clovis burial site in western Montana. Nature 2014. Pay per viewLINK [doi:10.1038/nature13025]

Abstract


Clovis, with its distinctive biface, blade and osseous technologies, is the oldest widespread archaeological complex defined in North America, dating from 11,100 to 10,700 14C years before present (bp) (13,000 to 12,600 calendar years bp)1, 2. Nearly 50 years of archaeological research point to the Clovis complex as having developed south of the North American ice sheets from an ancestral technology3. However, both the origins and the genetic legacy of the people who manufactured Clovis tools remain under debate. It is generally believed that these people ultimately derived from Asia and were directly related to contemporary Native Americans2. An alternative, Solutrean, hypothesis posits that the Clovis predecessors emigrated from southwestern Europe during the Last Glacial Maximum4. Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site in western Montana. The human bones date to 10,705 ± 35 14C years bp (approximately 12,707–12,556 calendar years bp) and were directly associated with Clovis tools. We sequenced the genome to an average depth of 14.4× and show that the gene flow from the Siberian Upper Palaeolithic Mal’ta population5 into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years bp. We also show that the Anzick-1 individual is more closely related to all indigenous American populations than to any other group. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly ancestral to many contemporary Native Americans. Finally, we find evidence of a deep divergence in Native American populations that predates the Anzick-1 individual.

Haploid DNA
The Y-DNA lineage of Anzick is Q1a2a1* (L54) to the exclusion of the common Native American subhaplogroup Q1a2a1a1 (M3). Among the modern compared sequences that of a Maya is the closest one.

The mtDNA belongs to the common Native American lineage D4h3a at its underived stage (root). 
For starters I must explain that these underived haplotypes can only be found within mtDNA and never in modern Y-DNA (common misconception) because this one accumulates mutations every single generation, while the much shorter mtDNA does only occasionally. Hypothetically we could find the exact ancestor of some modern Y-DNA haplogroup in ancient remains but that would be like finding the proverbial needle in the haystack. On the other hand, finding the underived stage in mtDNA, be it ancient or modern, does not mean that we are before a direct ancestor but just a non-mutated relative of her, who can be very distant in fact.


Autosomal DNA

In this aspect, the Anzick man shows clearly strongest affinities to Native Americans, followed at some distance by Siberian peoples, particularly those near the Bering Strait. 

Figure 2 | Genetic affinity of Anzick-1. a, Anzick-1 is most closely related to Native Americans. Heat map representing estimated outgroup f3-statistics for shared genetic history between the Anzick-1 individual and each of 143 contemporary human populations outside sub-Saharan Africa. (…)
However Anzick-1 shows clearly closer affinity to the aboriginal peoples of Meso, Central and South America (collectively labeled as SA) and less so to those of Canada and the American Arctic (labeled as NA). No data was available from the USA. 
This was pondered by the authors in several competing models of Native American ancestry:
Figure 3 | Simplified schematic of genetic models. Alternative models of the population history behind the closer shared ancestry of the Anzick-1 individual to Central and Southern American (SA) populations than Northern Native American (NA) populations; seemain text for further definition of populations. We find that the data are consistent with a simple tree-like model in which NA populations are historically basal to Anzick-1 and SA. We base this conclusion on two D-tests conducted on the Anzick-1 individual, NA and SA. We used Han Chinese as outgroup. a, We first tested the hypothesis that Anzick-1 is basal to both NA and SA populations using D(Han, Anzick-1; NA, SA). As in the results for each pairwise comparison between SA and NA populations (Extended Data Fig. 4), this hypothesis is rejected. b, Next, we tested D(Han, NA; Anzick-1, SA); if NA populations were a mixture of post-Anzick-1 and pre-Anzick-1 ancestry, we would expect to reject this topology. c, We found that a topology with NA populations basal to Anzick-1 and SA populations is consistent with the data. d, However, another alternative is that the Anzick-1 individual is from the time of the last common ancestral population of the Northern and Southern lineage, after which the Northern lineage received gene flow from a more basal lineage.
The most plausible model they believe is “c”, in which Anzick-1 is close to the origin of the SA population, while NA diverged before him. However model “d” in which Anzick-1 is close to the overall Native American root but NA have received further inputs from a mystery population (presumably some Siberians, related to the Na-Dené and Inuit waves) is also consistent with the data. Choosing between both “consistent” models (or something in between) clearly requires further investigation. 

Tianyuan and East Asian origins
All the above is very much within expectations, although refreshingly clarifying. But there is something in the formal tests (extended data fig. 5) that is most unexpected (but not discussed in the paper). 
The formal f3 tests of ED-fig.5 a to e fall all within reasonable expectations. Maybe the most notable finding is that, after all, the pre-Inuit people of the Dorset culture (represented by the Saqqaq remains) left some legacy in Greenland, but they also show some extra affinity with several Siberian populations (notably the Naukan, Chukchi, Koryak and Yukaghir, in this order) before to any other Native Americans, including Aleuts). 
But the really striking stuff is in figs. f and g, where it becomes obvious that the Tianyuan remains of Northern China show not a tad of greater affinity to East Asians (nor to Native Americans) than to West Eurasians. Also two East Asian populations (Tujia and Oroqen) are considerably more distant than the bulk of East Asian peoples to Tianyuan but also to Aznick.
Extended Data Figure 5 | Outgroup f3-statistics contrasted for different combinations of populations. (…) f, g, Shared genetic history with Anzick-1 compared to shared genetic history with the 40,000-year-old Tianyuan individual from China.
This is very difficult to explain, more so as Tianyuan’s mtDNA haplogroup B4’5 is part of the East Asian and Native American genetic pool, and the authors make no attempt to do it. 
The previous study by Qiaomei Fu et al. (open access) placed Tianyuan’s autosomal DNA near the very root of Circum-Pacific populations (East Asians, Native Americans and Australasian Aborigines) but after divergence from West Eurasians:
From Qiaomei Fu 2013
They even had doubts about the position of Papuans (the only Australasian representation) in that tree, which they suspected an artifact of some sort.
Since I saw that graph (h/t to an anonymous commenter at Fennoscandian Ancestry) I am squeezing my brain trying to figure out a reasonable explanation, considering that the formal f3 test has almost certainly more weight than the ML tree made with an algorithm. 
My first tentative explanation would be to imagine a shared triple-branch origin for Tianyuan, East Asians and West Eurasians, maybe c. 60 Ka ago (it must have been before the colonization of West Eurasia), to the exclusion of other, maybe isolated, ancient populations, whose admixture with the ancestors of the Tujia, Oroqen and Melanesians (maybe via Austronesians?) causes those striking low affinity values for these.
This would be a similar mechanism to the one explaining lower Tianyuan (and generally all ancient Eurasian) affinity for Palestinians (incl. Negev Bedouins) and also the Makrani, who have some African admixture and (in the Palestinian case) also, most likely, residual inputs from the remains of the first Out-of-Africa episode in Arabia.
However to this day we have no idea of which could be those hypothetical ancient isolated populations of East Asia. In normal comparisons such as ADMIXTURE analysis the Tujia and Oroqen appear totally normal within their geographic context, but this may be an artifact of not doing enough runs to reach higher K values, according to the cross-validation test, much more likely to discern the actual realistic components. 
The matter certainly requires further research, which may well open new avenues for the understanding the genesis of Eurasian populations, particularly those from the East.
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Medieval Germans, Hungarians and the spread of lactose tolerance

A new ancient DNA study found that 800 years ago in Dalheim (Western Germany) lactase persistence was already similar to modern day frequencies (h/t to Chad):
Annina Krüttli et al., Ancient DNA Analysis Reveals High Frequency of European Lactase Persistence Allele (T-13910) in Medieval Central Europe. PLoS ONE 2014. Open accessLINK 
[doi: 10.1371/journal.pone.0086251]

Abstract


Ruminant milk and dairy products are important food resources in many European, African, and Middle Eastern societies. These regions are also associated with derived genetic variants for lactase persistence. In mammals, lactase, the enzyme that hydrolyzes the milk sugar lactose, is normally down-regulated after weaning, but at least five human populations around the world have independently evolved mutations regulating the expression of the lactase-phlorizin-hydrolase gene. These mutations result in a dominant lactase persistence phenotype and continued lactase tolerance in adulthood. A single nucleotide polymorphism (SNP) at C/T-13910 is responsible for most lactase persistence in European populations, but when and where the T-13910 polymorphism originated and the evolutionary processes by which it rose to high frequency in Europe have been the subject of strong debate. A history of dairying is presumed to be a prerequisite, but archaeological evidence is lacking. In this study, DNA was extracted from the dentine of 36 individuals excavated at a medieval cemetery in Dalheim, Germany. Eighteen individuals were successfully genotyped for the C/T-13910 SNP by molecular cloning and sequencing, of which 13 (72%) exhibited a European lactase persistence genotype: 44% CT, 28% TT. Previous ancient DNA-based studies found that lactase persistence genotypes fall below detection levels in most regions of Neolithic Europe. Our research shows that by AD 1200, lactase persistence frequency had risen to over 70% in this community in western Central Europe. Given that lactase persistence genotype frequency in present-day Germany and Austria is estimated at 71–80%, our results suggest that genetic lactase persistence likely reached modern levels before the historic population declines associated with the Black Death, thus excluding plague-associated evolutionary forces in the rise of lactase persistence in this region. This new evidence sheds light on the dynamic evolutionary history of the European lactase persistence trait and its global cultural implications.

Table 2. Results of genetic sex and LP allele genotyping.

So lactase persistence was already highly prevalent in West-Central Germany 800 years ago, much as it is today.
Very interesting also is their mention of a previous study in Medieval Hungarians (Nagy 2011, PPV):

A study of medieval Hungary found moderate levels of LP in local
commoners (33%) ca. AD 900–1100, but extrapolating from these results is
complicated by the region’s history of conquest by lactase
non-persistent Asian invaders.

While these frequencies are clearly much higher than Neolithic ones (zero), they were still much lower than present day (c. 60%). 
They also mention the oldest know lactase persistence alleles in Europe, which correspond to Chalcolithic findings in Götland and the Basque Country, albeit still at low frequencies and, in the Basque case, showing strong linkage disequilibrium pointing to an initial admixture episode between two different populations: one lactose-tolerant and the other intolerant. See this previous entry for more details.
As I see it, these two data points help us to better understand the still very wide window when lactose tolerance spread among Europeans, which begins in the Chalcolithic and, at least in the case of Germany, seems closed by the Middle Ages. Although in the Hungarian case remained still half-way in that period. 
It is quite possible that instead of a single selective swap affecting this trait, the process took place in several bouts, each one with their own geography and timeline. 
Still, the reasons behind this apparent positive selection for milk-digesting genes, remain ill-explained at academic level. Recently I tried to articulate a consistent theory on it, based on the fact that the Metal Ages, when this sweep happened almost certainly, were characterized by the accumulation of agricultural resources, wealth and power in few hands, producing a class-structured society in which the vast majority were poor and lived precarious lives, in which the general availability of, particularly, goat milk may have been an important nutritional relief (calories and proteins). See: Is the ability to digest milk in Europeans caused by ancient social inequality?
 

Ancient European DNA and some debatable conclusions

There is a rather interesting paper still in preparation available online and causing some debate.
Iosif Lazaridis, Nick Patterson, Alissa Mittnik, et al., Ancient human genomes suggest three ancestral populations for present-day Europeans. BioArxiv 2013 (preprint). Freely accessibleLINK [doi:10.1101/001552]

Abstract

Analysis of ancient DNA can reveal historical events that are difficult to discern through study of present-day individuals. To investigate European population history around the time of the agricultural transition, we sequenced complete genomes from a ~7,500 year old early farmer from the Linearbandkeramik (LBK) culture from Stuttgart in Germany and an ~8,000 year old hunter-gatherer from the Loschbour rock shelter in Luxembourg. We also generated data from seven ~8,000 year old hunter-gatherers from Motala in Sweden. We compared these genomes and published ancient DNA to new data from 2,196 samples from 185 diverse populations to show that at least three ancestral groups contributed to present-day Europeans. The first are Ancient North Eurasians (ANE), who are more closely related to Upper Paleolithic Siberians than to any present-day population. The second are West European Hunter-Gatherers (WHG), related to the Loschbour individual, who contributed to all Europeans but not to Near Easterners. The third are Early European Farmers (EEF), related to the Stuttgart individual, who were mainly of Near Eastern origin but also harbored WHG-related ancestry. We model the deep relationships of these populations and show that about ~44% of the ancestry of EEF derived from a basal Eurasian lineage that split prior to the separation of other non-Africans.

Haploid DNA
The Lochsbour skull.
The prominent browridge
is very unusual for
Paleolithic Europeans.
The new European hunter-gatherer samples carried all Y-DNA I and mtDNA U5a and U2e.
More specifically, the hunter-gatherer mtDNA lineages are:
  • Lochsbour (Luxembourg): U5b1a
  • Motala (Sweden):
    • Motala 1 & 3: U5b1a
    • Motala 2 & 12: U2e1
    • Motala 4 & 6: U5a2d
    • Motala 9: U5a2
Additionally the Stuttgart Linear Pottery farmer (female) carried the mtDNA lineage T2c1d1.
The Y-DNA lineages are:
  • Lochsbour: I2a1b*(xI2a1b1, I2a1b2, I2a1b3)
  • Motala 2: I*(xI1, I2a2,I2a1b3)
  • Motala 3: I2*(xI2a1a, I2a2, I2b)
  • Motala 6: uncertain (L55+ would make it Q1a2a but L232- forces it out of Q1)
  • Motala 9: I*(xI1)
  • Motala 12: I2a1b*(xI2a1b1, I2a1b3)
These are with certainty the oldest Y-DNA sequences of Europe so far and the fact that all them fall within haplogroup I(xI1) supports the notion of this lineage being once common in the subcontinent, at least in some areas. Today I2 is most common in Sardinia, the NW Balcans (Croatia, Bosnia, Montenegro), North Germany and areas around Moldavia.
I2a1b (which may well be all them) is currently found (often in large frequencies) in the Balcans and Eastern Europe with some presence also in the eastern areas of Central Europe. It’s relative I2a1a is most common in Sardinia with some presence in SW Europe, especially around the Pyrenees. I2a1 (probably I2a1a but not tested for the relevant SNPs) was also found, together with G2a, in a Chalcolithic population of the Treilles group (Languedoc) and seems to be somehow associated to Cardium Pottery Neolithic.
If you want my opinion, I’d think that I2a before Neolithic was dominant, like mtDNA U5 (and satellites U4 and U2e), in much of Central and Eastern Europe but probably not in SW Europe, where mtDNA U5 seems not so much hyper-dominant either, being instead quite secondary to haplogroup H (at least in Western Iberia). But we’ll have to wait until geneticists manage to sequence Y-DNA in several SW European Paleolithic remains to be sure.

Autosomal DNA and derived speculations
Most of the study (incl. the must-read supplemental materials) deals however with the autosomal DNA of these and other hunter-gatherers, as well as of some Neolithic farmers from Central Europe and Italy (Ötzi) and their comparison with modern Europeans. 
To begin with, they generated a PCA plot of West Eurasians (with way too many pointless Bedouins and Jews, it must be said) and projected the ancient Europeans, as well as a whole bunch of Circum-Pacific peoples on it:
The result is a bit weird because, as you can see, the East Asians, Native Americans and Melanesians appear to fall way too close to the peoples of the Caucasus and Anatolia. This seems to be a distorting effect of the “projection” method, which forces the projected samples to align relative to a set of already defined parameters, in this case the West Eurasian (modern) PCA. 
So the projection basically formulates the question: if East Asians, etc. must be forcibly to be defined in West Eurasian (WEA) terms, what would they be? And then answers it as follows: Caucasian/Anatolian/Iranian peoples more or less (whatever the hidden reasons, which are not too clear).
Similarly, it is possible (but uncertain) that the ancient European and Siberian sequences show some of this kind of distortion. However I have found experimentally that the PCA’s dimension 1 (but not the dimension 2, which corresponds largely to the Asian-specific distinctions) still correlates quite well with the results of other formal tests that the authors develop in the study and is therefore a valuable tool for visualization.
But this later. By the moment the PCA is asking and answering three or four questions by projecting ancient European and Siberian samples in the West Eurasian plot:
  • If ancient Siberians are forced to be defined in modern WEA terms, what would they be? Answer: roughly Mordvins (Afontova Gora 2) or intermediate between these and North Caucasus peoples (Mal’ta 1).
  • If ancient Scandinavian hunter-gatherers are forced in modern WEA terms, what would they be? Answer: extreme but closest (Skoglund) to Northern European peoples like Icelanders or Lithuanians.
  • If ancient Western European hunter-gatherers are forced in modern WEA terms, what would they be? Answer: extreme too but closest (La Braña 2) to SW European peoples like Basques and Southern French.
  • If ancient Neolithic/Chalcolithic farmers from around the Alps and Sweden are forced in modern WEA terms, what would they be? Answer: Canarians (next close: Sardinians, then Spaniards).
Whatever the case, there seems to be quite a bit of autosomal diversity among ancient Western hunter-gatherers, at the very least when compared with modern peoples. This makes some good sense because Europe was a big place already in Paleolithic times and must have harbored some notable diversity. Diversity that we may well find to grasp if we only sample people from the same areas once and again.
On the other hand, they seem to cluster in the same extreme periphery of the European cluster, opposed to the position of West Asians, and therefore suggesting that there has been some West Asian genetic flow into Europe since then (something we all assume, of course). 
Using Lochsbour as proxy for the WHG (Western hunter-gatherer) component, Mal’ta 1 as proxy for the ANE (ancient north Eurasian) one and Stuttgart as proxy for the EEF (early European farmer) one, they produce the following graph (to which I added an important note in gray):
The note in gray is mine: highlighting the contradictory position where the other Western hunter-gatherers may fall in because of assuming Lochsbour as valid proxy, when it is clearly very extreme. This was not tested in the study so it is inferred from the PC1, which seems to best approach the results of their formal tests in the WHG vs EEF axis, as well as those of the WHG vs Near East comparisons.
I tried to figure out how these formal tests are reflected, if at all in the PCA, mostly because the PCA is a much easier tool for comprehension, being so visual. Eventually I found that the dimension 1 (horizontal axis) is very close to the genetic distances measured by the formal tests (excepted those for the ANE component, obviously), allowing a visualization of some of the possible problems caused by their use of Lochsbour as only reference, without any control. Let’s see it:

The same PCA as above with a few annotations in magenta and green
While not exactly, the slashed vertical magenta line (median in the dimension 1 between Lochsbour and Stuttgart) approximates quite well the WHG vs EEF values measured in the formal tests. Similarly, the slashed green axis (median in PC1 between Lochsbour and an good looking Bedouin) approximates to a great extent the less precise results of the formal tests the authors applied to guesstimate the West Asian and WHG ancestry of EEFs, which ranged between 60% and almost 100% West Asian (my line is much closer to the 60% value, which seems more reasonable). 
When I tried to find an alternative median WHG/West Asian line, using Braña 2 and the first non-Euro-drifted Turk I could spot (Anatolia is much more likely to be the direct source of West Asian ancestry in Europe than Bedouins), I got exactly the same result, so no need to plot any second option (two wrongs sometimes do make one right, it seems). But when I did the same with La Braña 2 and Stuttgart I got a genuine good-looking alternative median line, which is the slash-and-dot magenta axis.
This alternative line is probably a much more reasonable 50% WHG-EEF approximation in fact and goes right through Spain, what makes good sense for all I know.
Of course the ideal solution would be that someone performed good formal tests, similar to those done in the study, with Braña 2 and/or Skoglund, which should be more similar to the actual WHG ancestry of modern Europeans than the extremely divergent Lochsbour sequence. An obvious problem is that La Braña produced only very poor sequences but, well, use Skoglund instead or sample some Franco-Cantabrian or Iberian other Paleolithic remains.
Whatever the solution, I think that we do have a problem with the use of Lochsbour as only WHG proxy and that it demands some counter-testing. 
What about the ANE component? I do not dare to give any alternative opinion because I lack tools to counter-analyze it. What seems clear is that its influence on modern Europeans seems almost uniformly weak and that it can be ignored for the biggest part. As happens with the WHG, it’s quite possible that the ANE would be enhanced if the sequence from Afontova Gora is used instead of that of Mal’ta but I can’t foresee how much. 
Finally some speculative food-for-thought. Again using the visual tool of the PCA, I spotted some curiosities:

Speculative annotations on the PCA

Most notably it is apparent that the two WHG populations (Western and Scandinavian) are aligned in natural axes, which seem to act as clusters. Extending both (dotted lines) they converge at a point closest to some French, notably the only “French” that tends towards “Southern France” and Basques. So I wonder: is it possible that these two WHG cluster-lines represent derived ancient branches from an original population of SW France. We know that since the LGM, the area of Dordogne (Perigord) was like the megapolis of Paleolithic Europe, with population densities that must have been several times those of other areas. We know that this region was at the origin of both Solutrean and Magdalenian cultures and probably still played an important role in the Epipaleolithic period. 
So I do wonder: is that “knot” a mere artifact of a mediocre representation or is it something much more real? Only with due research in the Franco-Cantabrian region we will find out. 
 

Neanderthals, Denisovans and everything else

A recent analysis of the nuclear DNA of a Neanderthal toe from Altai has caused widespread interest.
Kay Prüffer et al., The complete genome sequence of a Neanderthal from the Altai Mountains. Nature 2013. Pay per viewLINK [doi:10.1038/nature12886]
The story of a finger and a toe
Both the Denisovan and Neanderthal DNA sequences discussed in this paper come from small bones found at the same location: Denisova cave, Altai Republic. The Denisovan sequence that revolutionized human paleogenetics a few years ago corresponds to a finger phalanx bone of some 50,000 years ago. The less notorious Neanderthal sequence discussed in this study corresponds to a toe imal phalanx, which was found in a lower layer in the same gallery of the same cave, and hence should be older.
This is very interesting to underscore because it seems to imply that Neanderthals were in Altai and specifically in Denisova cave very early, at dates similar to those we find in West Asia (Tabun excepted) and they may even be older than Denisovans in the very cave that gave them their name.
The toe sequence was found in a previous study to have Neanderthal mtDNA, closely related to the lineages of European Neanderthals of various dates and sites. Instead the finger mtDNA (Denisovan) was derived from a more ancient branch of humankind than the very point of split between Neanderthals and modern humans (H. sapiens) and has been recently shown to be related to European H. heidelbergensis from Atapuerca
Notes in red are mine.
This study focuses on the autosomal DNA of both Neanderthals and Denisovans. Unlike mtDNA, whose phylogenetic position is simple and quite straightforward, autosomal or nuclear DNA (nDNA) is extremely much more complex to understand because of its recombining nature, requiring of statistical approaches, which may get extremely complex and potentially subject to premise biases. When comparing two individuals this gets largely simplified but it is a lot more complex when doing the same with larger samples.
And that is precisely what this study does: comparing one Denisovan, several Neanderthals and also several modern humans. Therefore it is a very complex paper and the authors necessarily assume some evaluation risks, which nevertheless are discussed in depth in the supplemental material, a methodology of the Pääbo team that we can’t but greatly appreciate.
Age estimates
The study makes two age estimates, one based on a very conservative and truly unbelievable Pan-Homo split date of 6.5 Ma BP and the other based on observed per generation mutation rates, which happens to be perfectly coincident with a Pan-Homo split of 13 Ma BP, the oldest extreme of Langergraber’s estimate. This coincidence alone is of enough relevance for all molecular clock approaches, because it effectively demands the doubling of all age estimates based on the ridiculously short 6.5 Ma Pan-Homo split supposition. 
Red outlines are mine. Click to enlarge.
It also produces a semi-reasonable San-West African age estimate of c. 86-130 Ka, although I would think it a bit older in fact or at the very least at the top end. This highlights the severe difficulties of such molecular clock estimates, because a 4 Ma divergence between the alleged introgressing mystery archaic in the Denisovan genome, seems out of the question according on the archaeological and paleontological record, which only documents Homo species since c. 2 Ma ago, half that time (within the estimate but clearly very far from the top end).
Altai Neanderthal inbreeding
An important finding of this study is that the studied individual was extremely inbred, with parents in effective relationship comparable to that of grandparent and grandchild or half siblings. This inbreeding tendency, even if extreme, is not so strange in populations that have experienced founder effect bottlenecks and small population sizes. The Denisovan and the modern human Karitiana people are not so extreme but range in the lower end of double first cousins level of genetic relationship between the parents. Other Native Americans like the Mixe are close to that range, while the other compared populations, Papuans and Sardinians, show much lower levels of inbreeding.
Whatever we may think of Altai Neanderthal inbreeding, their drift parameter is still very low when compared with European Neanderthals. This is not discussed in the paper but such extreme drift also seems to imply extreme inbreeding issues in European Neanderthals, even if these may have other causes such as an extremely strong founder effect or whatever.
Bonobo-specific segments were removed, so the bonobo position is not realistic.
Inferred population history
Both populations leading to the Altai Neanderthal and Denisovans, but not modern humans, appear to have gone through a strong decline in population size since hundreds of millennia ago. The Denisovan decline seems to begin c. 800 Ka ago while the Neanderthal one may have begun c. 500 Ka ago. While this is coincident with a general expansion of the H. sapiens branch (still undifferentiated in Africa), peaking around c. 250 Ka ago before differentiation and relative decline. In their words:

All genomes analysed show evidence of a reduction in population size that occurred sometime before 1.0 million years ago. Subsequently, the population ancestral to present-day humans increased in size,whereas the Altai and Denisovan ancestral populations decreased further in size. It is thus clear that the demographic histories of both archaic populations differ substantially from that of present-day humans.

Neanderthal and Denisovan admixture in modern humans

The new tests confirm in essence the previous findings: there is significant Neanderthal introgression in modern humans descending from the migrants out of Africa and there is also significant Denisovan one among Australasian populations.

Additionally and with some caution, the authors think that much lesser Denisovan introgression (of around 0.2%) is found among East Asians and that these, as well as Native Americans, show slightly more Neanderthal admixture than West Eurasians. In my understanding this may be caused by minor African flow to West Eurasia after the admixture event (and/or residual “First Arabian” persistence) and I would think that measuring South Asians would help to clarify this issue (because African admixture is negligible in the subcontinent but they are also distinct from East Asians).

These measurements are so weak that the authors agree to all kind of cautions about them in any case.

In addition to all this, the supplemental material (section 13) also detects tiny, almost homeopathic, amounts of Neanderthal gene flow to Yorubas (~0.02%), obviously mediated by H. sapiens backflow from Asia and Europe into parts of Africa, which eventually influenced other African populations. An even more diluted amount may also be present among the Mbuti Pygmies.

Altai Neanderthal admixture in Denisovans

This issue is not really explained in the paper as such, and we have to reach out to the Supplemental Information chapter 15 in order to grasp it.

It is clear that the Altai Neanderthals are closer to Denisovans than other Neanderthals are by approx. the following fractions (directly deduced from the raw affinities listed in fig. S6a.2):

  • 2% more than Mezhmaiskaya
  • 7% more than Vindija (avg.)
  • 9% more than El Sidrón
Feldhofer appears closer instead but this sequence was not used by the authors in most tests because it has too dubious quality.

In section 15 of the supplementary material, using complex methodology and lamenting the lack of a second Denisovan sample which would be most useful, they estimate a minimal 0.5% (Altai) Neanderthal introgression in Denisovans, with strong warnings that this could well be quite higher. I don’t know why they are not even considering a more direct approach, but I would dare to guesstimate the introgression to be close to 8% from the above raw data, assuming that there are no further complexities at play, such as other Heidelbergensis introgression in European Neanderthals, etc. The drift parameter (see above) does not seem to be one such complexity because Mezhmaiskaya is almost as drifted as Vindija yet it is consistently much closer, as it seems to correspond to its specific relatedness to Altai Neanderthals in mtDNA (and possibly also in nDNA if it is admixture what causes their pseudo-tree positioning closer to the root, what would be typical).

Note in blue is mine.

Mystery archaic genetic flow into Denisovans

The authors find that some 0.5-8% of the Denisovan genome appears to come from another hominin, which split from the human trunk even earlier.

We caution that these analyses make several simplifying assumptions. Despite these limitations, we show that the Denisova genome harbors a component that derives from a population that lived before the separation of Neanderthals, Denisovans and modern humans. This component may be present due to gene flow, or to a more complex population history such as ancient population structure maintaining a larger proportion of ancestral alleles in the ancestors of Denisovans over hundreds of thousands of years.


Later in the discussion section they ponder further the implications of this finding:

The evidence suggestive of gene flow into Denisovans from an unknown hominin is interesting. The estimated age of 0.9 to 4 million years for the population split of this unknown hominin from the modern human lineage is compatible with a model where this unknown hominin contributed its mtDNA to Denisovans since the Denisovan mtDNA diverged from the mtDNA of the other hominins about 0.7–1.3 million years ago41. The estimated population split time is also compatible with the possibility that this unknown hominin was what is known from the fossil record as Homo erectus. This group started to spread out of Africa around 1.8 million years ago42, but Asian and African H. erectus populations may have become finally separated only about one million years ago43. However, further work is necessary to establish if and how this gene flow event occurred.


Going to the detail of the matter (i.e. supplemental material sections 16a and 16b), one of the key details is that present-day Africans share more derived alleles with Neanderthals than with Denisovans. This can only be explained because Denisovans have other archaic ancestry prior to their apparent divergence from Neanderthals or (what is about the same) because Denisovans diverged themselves prior to the Neanderthal-Sapiens split, what is what the mtDNA (unlike the nDNA) suggests. However the difference, even if consistent across comparisons, is too small (a few percentage points) to be attributed to the later scenario.

This means that Denisovans appear to be at nDNA level some sort of an independent branch of proto-Neanderthals with some other but minor archaic admixture. Instead at mtDNA level they appear to be unrelated to Neanderthals and related instead to H. heidelbergensis (a detail not discussed in this paper because it is a too recent independent discovery).

There are still many details to explore but, in principle, it would seem that the Denisovan branch appears to be a divergent proto-Neanderthal one (maybe related to the Hathnora hominin, which looks very much Neanderthal) with lesser other archaic (H. heidelbergensis?) admixture, which nevertheless remained prominent in their mtDNA for whatever accidental reason.

Whether the H. heidelbergensis population of Atapuerca responds to this same profile (i.e. they were Denisovans too) or belongs instead to the “other archaic” population which introgressed in the Denisovan genome remains to be solved. So far we only know the mitochondrial lineage and this one may be misleading, as seems to be the case with the Denisova hominin.

Note in red is mine

Modern human genetic evolution

Benefiting from the high quality of the archaic genomes of Altai, the authors cataloged a long list of simple mutations exclusive to our species: 31,389 single nucleotide substitutions and 4,113 short insertions and deletions (indels). Additionally they found other 105,757 substitutions and 3,900 indels shared by 90% of their modern human sample of 1094 individuals.

They suggest some lines for future research in this regard, maybe focusing on genes known to influence brain development or regions that could show signs of positive selection. These preliminary lines of research are explored in SI-20, noticing potential selection in genes that affect the ventricular zone of the brain and cell proliferation in fetal brain development.

 

The Mal’ta aDNA findings

The recent sequencing of ancient DNA from the remains of a Central Siberian young boy, corresponding to the Gravettian site of Mal’ta, West of Lake Baikal, dated to c. 24,000 years calBP, has caught the interest of many anthropology enthusiasts. During my hiatus of more than two months, most people who asked me to retake blogging with an specific request, talked of these findings. Let’s see:
Maanasa Raghavan et al., Upper Palaeolithic Siberian genome reveals dual ancestry of Native Americans. Nature 2013. Pay per viewLINK [doi:10.1038/nature12736]

Abstract

The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians1, 2, 3, there is no consensus with regard to which specific Old World populations they are closest to4, 5, 6, 7, 8. Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal’ta in south-central Siberia9, to an average depth of 1×. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers10, 11, 12, and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages5. Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians2, 13. Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago14, revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.

Haploid lineages
The Mal’ta boy, MA-1, carried distinct yDNA R* and mtDNA U* lineages. While both are clearly related to those dominant in Europe and parts of Asia (West, South) nowadays, they are also distinct from any specific dominant lineage today.
R* (yDNA) is neither R1 nor R2 but another distinct branch of R. This kind of R(xR1, R2) is most rare today and found mostly in and around NW South Asia. Following Wikipedia, this “other R” is found in:
  • 10.3% among the Burusho
  • 6.8% among the Kalash
  • 3.4% among the Gujarati
However I must say that I recall from old discussions that some R(xR1) is also found among Mongols and some North American Natives. I would have to find the relevant studies though (maybe in an update).
U* (mtDNA) is also quite rare today but has been found in Swabian Magdalenian hunter-gatherers, as well as in some Neolithic samples, although it may well be a totally different kind of U* (I could not discern the specific markers in the paper nor the supplementary materials and it must be reminded that the asterisk only means “others”).
Autosomal DNA
The study also shows some statistical inferences from the autosomal (or nuclear) DNA of the Mal’ta boy:
Figure 1 [b & c]
b, PCA (PC1 versus PC2) of MA-1 and worldwide human populations for which genomic tracts from recent European admixture in American and Siberian populations have been excluded19.
c, Heat map of the statistic f3(Yoruba; MA-1, X) where X is one of 147 worldwide non-African populations (standard errors shown in Supplementary Fig. 21). The graded heat key represents the magnitude of the computed f3 statistics.

Here we can appreciate that MA-1 is closest to Native Americans but still rather intermediate between them and South and West Eurasians. Interestingly East Asians are quite distant instead, suggesting that MA-1 was still not too much admixed with that continental population, unlike what happens with Native Americans, who are essentially East Asian in the autosomal and mtDNA aspects. So this kid appears to be some sort of a “missing link” in the Paleolithic ethnogenesis of Native Americans.

Figure 2 | Admixture graph for MA-1 and 16 complete genomes. An admixture graph with two migration edges (depicted by arrows) was fitted using TreeMix21 to relate MA-1 to 11 modern genomes from worldwide populations22, 4 modern genomes produced in this study (Avar, Mari, Indian and Tajik), and the Denisova genome22. Trees without migration, graphs with different number of migration edges, and residual matrices are shown in Supplementary Information, section 11. The drift parameter is proportional to 2Ne generations, whereNe is the effective population size. The migration weight represents the fraction of ancestry derived from the migration edge. The scale bar shows ten times the average standard error (s.e.) of the entries in the sample covariance matrix. Note that the length of the branch leading toMA-1 is affected by this ancient genome being represented by haploid genotypes.
Even if I am not too keen of TreeMix, in this case the results seem consistent.
We can appreciate here that a sample of Native Americans (the Karitiana, maybe not as “pure” as the Xavantes but still very much so) show up in a different branch from MA-1, reflecting their overwhelmingly East Asian ancestry, mostly by the maternal side (mtDNA). MA-1 instead hangs from the South-West Eurasian branch, soon after the split between South Asians and West Eurasians. Both have extremely drifted branches, surely indicating the small size of their founder populations, typical of the Far North. 
In addition to this basic tree, two admixture events are signaled: one is the already known Denisovan (H. erectus?) weak one into Australasian Natives (represented by Papuans) and the other one, quite more intense, is the one hanging from upstream of MA-1 to Native Americans (Karitiana), reflecting the partial South-West Eurasian ancestry of Native Americans (noticeable also in their dominant paternal ancestry: haplogroup Q). 
The fact that the admixture signal stems from quite upstream of MA-1 indicates that this boy (or rather his relatives) were not direct ancestors of Native Americans in any significant way but rather a different branch from the same trunk. Probably proto-Amerindians were already in this period at the North Pacific coasts, not sure if in Beringia or around Okhotsk or what but certainly they had already separated from the Mal’ta population.
What did we know of Native American genesis before this finding?
There are three principal lines of evidence:
  1. Y-DNA, which among Native Americans is essentially haplogroup Q (plus some C3, which is from NE Asia). By phylogenetically hierarchical diversity, haplogroup Q must have coalesced in West or Central Asia (or maybe South Asia?), very possibly in or near Iran. The NE Asian and Native American branches are clearly derived, even if more important numerically today.
  2. mtDNA, which among Native Americans is essentially from NE Asia (A, C, D), middle East Asia (B) but also in a small amount from West Asia (X2). 
  3. Archaeology: we can track, more or less directly, the proto-NAs by means of following the Upper Paleolithic sequence in Siberia and nearby areas. 
    1. C. 47,000 years ago (calBP) H. sapiens with Aurignacoid technology (i.e. linked to West Eurasian earliest Upper Paleolithic) reached Altai, displacing the Neanderthals to the Northern fringes of the district.
    2. C. 30,000 years ago, Upper Paleolithic (“mode 4”) technology with roots in Altai reached other parts of Siberia, Mongolia and North China, from where it expanded eastwards and southwards gradually in a process of, probably, cultural diffusion. 
    3. By c. 17,000 years ago they were already in North America and c. 15,000 years ago in South America. In the LGM they were probably in Beringia already (but this is only indirectly attested so far). 
So we already had a good idea about the origins of Native Americans: their ultimate roots, at least patrilineally, seem to be in Altai (where they were part of the wider West Eurasian colonization at the expense of Neanderthals with Aurignacian-like technology and dogs). Then, probably around 30,000 years ago they expanded eastwards through Siberia and maybe nearby areas, entering in intense and intimate contact with the already existent East Asian populations, with whom they admixed once and again, mostly by the female side. 
It would seem therefore that their society was already patrilocal because otherwise their patrilineages would have just got dissolved among the locals and would have never reached Beringia nor America in such dominant position.
Overall this is the quite clear notion that I have on Native American earliest genesis and for me there is no reasonable doubt about this narrative (except maybe in the fine details). However I must reckon that some individuals have reacted very negatively against it. But no matter how much they yell, I fail to see their arguments. 
How does this new finding affects this narrative?
It simply confirms it with further evidence. By 24,000 calBP the proto-NAs were surely already, as I said before, in NE Asia close to the Pacific coasts, so this Mal’ta population is a branch left behind in their migration (plus whatever new inflows from the West, which we can’t evaluate). The very low affinity level with East Asians, in spite of its quite Eastern location, shows that early East Asians had not yet reached, at least in significant numbers, so far North. If they had, they probably did only at more eastern longitudes, probably near the sea, where resources were more plentiful.
In other words: the first Central Siberians were of South+West Eurasian stock and the current East Asian genetic and phenotype hegemony in that area reflects post-LGM flows, mostly lead by yDNA N1. 
Early Native Americans were the product of admixture of these earliest Siberians with NE Asians, admixture that surely happened East of Lake Baikal, although the exact details are still unclear. 
What does MA-1 say about the West?
His mtDNA is generally consistent with other common U-derived lineages found in West Eurasian Upper Paleolithic, so not much other than he was somehow related, what is confirmed by autosomal analysis. 
His yDNA is more interesting maybe, nonetheless because it is probably the oldest sequence of this kind but also because it belongs to haplogroup R. It certainly discards whatever “molecular clock” guesstimates for R that are shorter than this site’s age but on its own it is not able to set a real age other than a bare minimum. 
So for example Eupedia‘s estimate of 29 Ka for R as such could still be valid, although I would say that extremely unlikely. 
Indirectly however it does say something by confirming the overall narrative of Native American origins as above and that means that Eupedia’s estimate of a mere 24 Ka age for haplogroup Q is almost certainly wrong by a lot. 
Using that tree, we would have to at least double the age of Q in order to fit with the Altai narrative (which begins at c. 47 Ka ago), what, extrapolating, implies an age for R of at least 58 Ka. I have estimated some 48 Ka of age for R1 and 68 Ka for P, so it makes good sense after these so necessary corrections. The exact ages we may never know but the approximate ages should be something like these. 
And that’s about all I can say. More in comments (and/or updates) if need be.

Update (Dec 6): R* and P* (and other rare clades) among Central Asians

A reader sent me copy of the study by Wei-Hua Shou et al. (2010) titled Y-chromosome distributions among populations in Northwest China identify significant contribution from Central Asian pastoralists and lesser influence of western Eurasians, published by Nature (doi:10.1038/jhg.2010.30).

While it is not the bit of info I was recalling above, it does add some information about unmistakable R(xR1,R2) and P(xQ,R) among Central Asian populations (from P.R. China territory). In detail:

  • R* is found in 5/31 Tayiks, 1/41 Kazakhs and 1/50 Uyghurs.
  • P* is found in 1/31 Tayiks and 1/43 Kirgizes. 

Also of interest should be the presence of:

  • Q(xQ1) in  8/35 Dongxiang (a Mongol ethnicity), 1/45 Kirgizes and 1/50 Tu (another Mongol ethnicity).
  • F(xG,H,I,J,K) in 2/32 Yugu (Yugurs, a distinct Uyghur sub-ethnicity), 2/41 Kazakh, 1/31 Tayiks and 1/50 Tu.
  • K(xN,O,P) in  32/533 total (i.e. 6% in Easternmost Central Asia), among which are most notable: 9/50 Uyghurs, 6/23 Uzbeks, 6/27 Bao’an (another small Mongol ethnicity), 3/32 Xibo (a Tungusic ethnicity), 2/32 Yugu and 2/5 Mongols. I guess that it is possible that this is a distinct K subclade, although it can well be either part of MNOPS (NO*?) or also belong to LT (L?).
  • R2 in 1/31 Tayiks and 2/27 Bao’an.
 

HERC2 haplotypes worldwide study at Kurdish DNA

I must congratulate again Palisto of Kurdish DNA blog for his excellent work on the description of HERC2 haplotypes and their frequency across world populations. It is not a peer-reviewed academic paper but it could well be, and within the high quality sector.
Palisto, The color of the eyes: at least 17 HERC2 variants in Human gene pool. Kurdish DNA 2013. Freely accessible blog articleLINK
After initially detecting seven haplotypes in the Kurdish genetic pool (which were named ht1-7) and then studying these in the Eurasian gene pool, he decided to study the African haplotypes, largely in the “other” category, as well as comparing them all with the known Neanderthal and Denisovan sequences, at the very least to infer a root. The main result is this tree:
So the ancestral haplotype is ht13, found not just among Neanderthals and Denisovans, but also among scattered populations of H. sapiens both in Africa as in Eurasia-plus. 
From it hang ht8 (Homo sapiens, found in and outside Africa) and ht18 (Neanderthal-exclusive).
This main branch has two major sub-haplogroups, which I will label D and E for convenience (A would be ht13, B ht8, and C Neanderthal-only ht18). Haplogroup D (hts 11, 16 and 17) seems to have remained in Africa (only ht 11 was detected at low frequencies in Lebanon), while haplogroup E (all the rest) massively participated in the migration out of Africa (OoA).
However it must have done already in highly diversified form, as most named haplotypes are found at significant frequencies both outside and inside Africa. There are four exceptions only:
  1. Ht9 is only found in Africa (with a minor Arabian exception), so this haplotype did not took part in the OoA.
  2. Ht15 has not been found in Africa instead, so it is possible that it evolved already in Eurasia.
  3. Ht2 and its descendant ht1 (both of which cause blue eyes, albeit in recessive manner) don’t seem to exist in Africa either (with the exception of the HGDP San sample, which seems notably admixed with Europeans, at levels of almost 20%, not your typical Bushmen really), so again they probably arose already in Eurasia. 
These are the wider regional frequencies:

However at the original article there is a much more detailed list, which is probably more interesting to use when pondering each haplotype. For example the overall data for America is pretty much irrelevant, as it groups native peoples with mixed creole ones.
For example we can see that “blue eyes” ancestral haplotype ht2 looks like originated in West Asia, and it may also be the case of its descendant ht1. 
Ht 15 in turn may well have coalesced in Altai, from where it spread to mostly Native American peoples (represented by Mestizo Colombians). A similar pattern can be seen in ht14, however this must be original from Africa (the Biaka have it, as do Mozabites) and therefore it is found also in some other scattered populations like Cambodians, Sindhi, etc.
Something I wonder about is the low diversity displayed by East Asians in this haplotype. Or inversely, why did West Eurasians evolve so all non-African novel variants? While there is still some left to analyze in the ND box, it is very small in East Asia. I wonder if it has some relation with skin pigmentation pathways indirectly influencing this change somehow.
 

The less homogeneous European "populations" are Italians and French

This comes from a recent IBD study on Europe:
Peter Ralph & Graham Coop, The Geography of Recent Genetic Ancestry across Europe. PLoS Biology, 2013. Open accessLINK [doi:10.1371/journal.pbio.1001555] 

Abstract

The recent genealogical history of human populations is a complex mosaic formed by individual migration, large-scale population movements, and other demographic events. Population genomics datasets can provide a window into this recent history, as rare traces of recent shared genetic ancestry are detectable due to long segments of shared genomic material. We make use of genomic data for 2,257 Europeans (in the Population Reference Sample [POPRES] dataset) to conduct one of the first surveys of recent genealogical ancestry over the past 3,000 years at a continental scale. We detected 1.9 million shared long genomic segments, and used the lengths of these to infer the distribution of shared ancestors across time and geography. We find that a pair of modern Europeans living in neighboring populations share around 2–12 genetic common ancestors from the last 1,500 years, and upwards of 100 genetic ancestors from the previous 1,000 years. These numbers drop off exponentially with geographic distance, but since these genetic ancestors are a tiny fraction of common genealogical ancestors, individuals from opposite ends of Europe are still expected to share millions of common genealogical ancestors over the last 1,000 years. There is also substantial regional variation in the number of shared genetic ancestors. For example, there are especially high numbers of common ancestors shared between many eastern populations that date roughly to the migration period (which includes the Slavic and Hunnic expansions into that region). Some of the lowest levels of common ancestry are seen in the Italian and Iberian peninsulas, which may indicate different effects of historical population expansions in these areas and/or more stably structured populations. Population genomic datasets have considerable power to uncover recent demographic history, and will allow a much fuller picture of the close genealogical kinship of individuals across the world.

Most interesting in my understanding is table 1 (right), which describes the IBD relation of the sampled populations within themselves and with other Europeans.
From this table it seems very apparent that Italians and French are not homogeneous at all and therefore, in my opinion, should not be treated as single populations in genetic studies but butchered at least a bit by regions (whose optimal dimensions are yet to be determined).
The degree of internal homogeneity of the samples (only n=5 or greater) can be simplified as follows:
  • Very low (<1): Italy, France.
  • Quite Low (1-1.4): Germany, UK, Belgium, England, Austria, French-Swiss, 
  • Somewhat low (1.5-1.9): Spain, German-Swiss, Greece, Portugal, Netherlands, Hungary.
  • Somewhat high (2-2.9): Czech R., Romania, Scotland, Ireland, Serbia, Croatia,
  • Quite high (3-3.9): Sweden, Poland
  • Very high (4-5): Bosnia, Russia*
  • Extremely high (>10): Albania
Notes: 
  • I ignored strangely labeled samples like “Switzerland” and “Yugoslavia”, which seem to mean actually “other” within these labels.  I retained the “United Kingdom” category for its large sample size, much larger than its obvious parts.
  • The level of relatedness of Russians may be exaggerated by the small sample: n=6, still above my cautionary threshold. 
  • I suspect that the extreme disparity of sample sizes may influence the results to some extent.
Eastern Europeans seem much more strongly related with others, especially other Eastern Europeans, than Western ones, while NW Europeans are more related with other groups (usually at regional level) than SW ones. In fact the Italian and Iberian peninsula show very low levels of “recent” relatedness with other populations, which is a bit perplexing, considering their non-negligible roles in Medieval and Modern European history. I guess that this may be partly caused by geographic barriers (mountains) and also by these areas having large populations since Antiquity or before. 

Figure 3. Geographic decay of recent relatedness.
In all figures, colors give categories based on the regional groupings of Table 1. (A–F) The area of the circle located on a particular population is proportional to the mean number of IBD blocks of length at least 1 cM shared between random individuals chosen from that population and the population named in the label (also marked with a star). Both regional variation of overall IBD rates and gradual geographic decay are apparent. (G–I) Mean number of IBD blocks of lengths 1–3 cM (oldest), 3–5 cM, and >5 cM (youngest), respectively, shared by a pair of individuals across all pairs of populations; the area of the point is proportional to sample size (number of distinct pairs), capped at a reasonable value; and lines show an exponential decay fit to each category (using a Poisson GLM weighted by sample size). Comparisons with no shared IBD are used in the fit but not shown in the figure (due to the log scale). “E–E,” “N–N,” and “W–W” denote any two populations both in the E, N, or W grouping, respectively; “TC-any” denotes any population paired with Turkey or Cyprus; “I-(I,E,N,W)” denotes Italy, Spain, or Portugal paired with any population except Turkey or Cyprus; and “between E,N,W” denotes the remaining pairs (when both populations are in E, N, or W, but the two are in different groups). The exponential fit for the N–N points is not shown due to the very small sample size. See Figure S8 for an SVG version of these plots where it is possible to identify individual points.
We can also see in the above figure (bottom) how most of the relatedness, especially along longer distances belongs to the oldest dates (1-3 cM).
The authors suggest that low heterogeneity within some of these groupings is influenced by regional variation, what makes good sense to me. This they illustrate with the examples of Italy and Great Britain:

Figure 2. Substructure in (A) Italian and (B) U.K. samples.
The leftmost plots of (A) show histograms of the numbers of IBD blocks that each Italian sample shares with any French-speaking Swiss (top) and anyone from the United Kingdom (bottom), overlaid with the expected distribution (Poisson) if there was no dependence between blocks. Next is shown a scatterplot of numbers of blocks shared with French-speaking Swiss and U.K. samples, for all samples from France, Italy, Greece, Turkey, and Cyprus. We see that the numbers of recent ancestors each Italian shares with the French-speaking Swiss and with the United Kingdom are both bimodal, and that these two are positively correlated, ranging continuously between values typical for Turkey/Cyprus and for France. Figure (B) is similar, showing that the substructure within the United Kingdom is part of a continuous trend ranging from Germany to Ireland. The outliers visible in the scatterplot of Figure 2B are easily explained as individuals with immigrant recent ancestors—the three outlying U.K. individuals in the lower left share many more blocks with Italians than all other U.K. samples, and the individual labeled “SK” is a clear outlier for the number of blocks shared with the Slovakian sample.
In the UK, there is a negative correlation between blocks shared with Ireland and those shared with Germany, what seems to imply a dual origin of Britons. 
Age estimates (double them?):
The authors also get to estimate ages, however it seems obvious from their own data that the results should be multiplied by 2.2 or something like that to make good sense:

Figure 4. Estimated average number of most recent genetic common ancestors per generation back through time.
Estimated average number of most recent genetic common ancestors per generation back through time shared by (A) pairs of individuals from “the Balkans” (former Yugoslavia, Bulgaria, Romania, Croatia, Bosnia, Montenegro, Macedonia, Serbia, and Slovenia, excluding Albanian speakers) and shared by one individual from the Balkans with one individual from (B) Albanian-speaking populations, (C) Italy, or (D) France. The black distribution is the maximum likelihood fit; shown in red is smoothest solution that still fits the data, as described in the Materials and Methods. (E) shows the observed IBD length distribution for pairs of individuals from the Balkans (red curve), along with the distribution predicted by the smooth (red) distribution in (A), as a stacked area plot partitioned by time period in which the common ancestor lived. The partitions with significant contribution are labeled on the left vertical axis (in generations ago), and the legend in (J) gives the same partitions, in years ago; the vertical scale is given on the right vertical axis. The second column of figures (F–J) is similar, except that comparisons are relative to samples from the United Kingdom.

I say that mainly because the shared ancestry between Balcans and both Italy and France is dated here to around 3000 or 3500 years ago, when it would fit much better to c. 7500 years ago (as much as 8000 BP for some parts of Italy), when the Neolithic expansion was ongoing. There is no particular reason why the Balcans would be related to France and Italy c. 3000 years ago specifically, unless one believes in undocumented massive Mycenaean migrations or something like that (and what about Albania then?)
However I am getting a headache with this issue because no correction, low or high seems good enough for all pairs, so, well, just take this part with your usual dose of healthy skepticism.
Some (annotated) excerpts:


In most cases, only pairs within the same population are likely to share genetic common ancestors within the last 500 years [i.e.: ~1100 years]. Exceptions are generally neighboring populations (e.g., United Kingdom and Ireland). During the period 500–1,500 ya [i.e. ~1100-3300 years ago: most of the Metal Ages], individuals typically share tens to hundreds of genetic common ancestors with others in the same or nearby populations, although some distant populations have very low rates. Longer ago than 1,500 ya [i.e. before ~3300 years ago: before the Late Bronze Age crisis], pairs of individuals from any part of Europe share hundreds of genetic ancestors in common, and some share significantly more.

On Italy:

There is relatively little common ancestry shared between the Italian peninsula and other locations, and what there is seems to derive mostly from longer ago than 2,500 ya [i.e. ~5500 y.a.: Megalithic era onwards]. An exception is that Italy and the neighboring Balkan populations share small but significant numbers of common ancestors in the last 1,500 years [i.e. after 3750 years: since the Mycenaean period]

On Iberia:

Patterns for the Iberian peninsula are similar, with both Spain and Portugal showing very few common ancestors with other populations over the last 2,500 years [i.e. 5500 years: Megalithic era onwards]. However, the rate of IBD sharing within the peninsula is much higher than within Italy… 

The low Iberian relationship with other populations seems to preclude this region as source for the conjectured re-expansion of mtDNA H and other Western lineages. I would suggest looking to (Western) France for an alternative source, as this state’s heterogeneous population shares more intense relations with other Western peoples around what could be c. 6200 BP, what is at the very beginning of Megalithic spread in Atlantic Europe, for which Armorica (Brittany and neighboring Western France) could well have been a major source (and definitely was in the case of Britain).
Of course, if you prefer to use the authors’ estimates, it would have no influence on the hypothesis because they simply can’t reach so far back in time, it seems. But I feel more comfortable overall reformulating the hypothesis towards Armorica.
For better reading of each pair of relationships through time, I include here fig. S16:

The maximum likelihood history (grey) and smoothest consistent history (red) for all pairs of population groupings of Figure S12 (including those of Figure 5). Each panel is analogous to a panel of Figure 4; time scale is given by vertical grey lines every 500 years. For these plots on a larger scale, see Figure S17.

As said before, I suggest to read each vertical grey line (counting from left) as meaning ~1100 years rather than just 500.

Update (Jun 23): on IBD-based molecular-clock-o-logy:

I have now and then found strange insistence on IBD-based chronological estimates being almost beyond reasonable doubt. I admittedly don’t know a great deal on the matter, so when Davidski (see comments) insisted again on that, I asked him for a reference, so I could learn something. He kindly suggested me to read Gusev et al. 2011, The Architecture of Long-Range Haplotypes Shared within and across Populations, which is indeed a good paper. However I could not find the clearly explained basis for the chronological estimates in general, probably buried deep in the bibliography. What I found instead was a clear example of these being short from historical reality by a lot.

This example corresponds to one of the best documented populations to have suffered a “recent” bottleneck event: Ashkenazi Jews (AJ). According to Gusev et al., these would have suffered a bottleneck (founder effect of some 400 nuclear families followed by expansion) around 20 generations ago (~600 years = 1400 CE) or, a few lines later more specifically: 23 generations ago (~1320 CE). So here we do have a clear case study.

When we look at historical reality however, it is just impossible that AJ would have their founder effect bottleneck so late. Historical records document them often already in the Frankish period and they were definitely a vibrant expanding community by the time of the founding of Prague and Krakov c. 900 CE. A historical reasonable estimate for the AJ founder effect should be instead c. 700 CE, when they begin to appear in historical records, or maybe even a bit earlier, because of the lack of documentation in the Dark Ages.

That is not at all a mere 20-23 generations ago but almost double (counting generation time = 30 years, if gen-time would be 27 years, for example, the difference between estimates and reality would be even greater). Assuming a very reasonable AJ founder effect at 700 CE, then:

  • For gen-time = 30 years → 43 generations till now → 43/23 = 1.9 times for realistic correction
  • For gen-time = 27 years → 48 generations → 48/23 = 2.1 times for realistic correction
  • For gen-time = 25 years → 52 generations → 52/23 = 2.3 times for realistc correction

While it has become nowadays standard issue to assimilate generation time to 30 years, this is not any absolute measure because the actually observed generation time (i.e. the age difference between parental and child generations on average) varies in real life depending on cultural factors (such as marriage age), gender (female generation time is almost invariably shorter than male), life expectancy (mothers dead at birth at young age, for example, don’t have any more children), etc. So it is in the fine detail a somewhat blurry issue, with some significant variability among cultures and surely also through time.

Another issue is if this “short term” estimate correction is stable along time or does in fact vary somewhat. I can’t say.

Whatever the case, the approximate x2 correction proposed above, seems to stand in general terms.