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Category Archives: population genetics

SW African Bantu matrilineages

Prolific researcher Chiara Barbieri has put online another interesting study on African genetics, this time about the Bantu populations of Southwestern and Central-Southern Africa (i.e. Namibia, Angola, Botswana and Zambia).
Chiara Barbieri et al., Migration and interaction in a contact zone: mtDNA variation among Bantu-speakers in southern Africa. bioRXiv 2014. Freely accessible (pre-pub) → LINK

ABSTRACT

Bantu speech communities expanded over large parts of sub-Saharan Africa within the last 4000-5000 years, reaching different parts of southern Africa 1200-2000 years ago. The Bantu languages subdivide in several major branches, with languages belonging to the Eastern and Western Bantu branches spreading over large parts of Central, Eastern, and Southern Africa. There is still debate whether this linguistic divide is correlated with a genetic distinction between Eastern and Western Bantu speakers. During their expansion, Bantu speakers would have come into contact with diverse local populations, such as the Khoisan hunter-gatherers and pastoralists of southern Africa, with whom they may have intermarried. In this study, we analyze complete mtDNA genome sequences from over 900 Bantu-speaking individuals from Angola, Zambia, Namibia and Botswana to investigate the demographic processes at play during the last stages of the Bantu expansion. Our results show that most of these Bantu-speaking populations are genetically very homogenous, with no genetic division between speakers of Eastern and Western Bantu languages. Most of the mtDNA diversity in our dataset is due to different degrees of admixture with autochthonous populations. Only the pastoralist Himba and Herero stand out due to high frequencies of particular L3f and L3d lineages; the latter are also found in the neighboring Damara, who speak a Khoisan language and were foragers and small-stock herders. In contrast, the close cultural and linguistic relatives of the Herero and Himba, the Kuvale, are genetically similar to other Bantu-speakers. Nevertheless, as demonstrated by resampling tests, the genetic divergence of Herero, Himba, and Kuvale is compatible with a common shared ancestry with high levels of drift and differential female admixture with local pre-Bantu populations.

Figure 1: Map showing the rough geographical location of populations, 
colored by linguistic affiliation. Abbreviations of population labels are 
as specified in Table 1.

In spite of the Bantu-centric approach of the study, which also has its merits, my greatest interest is rather in the less typically Bantu lineages, which speak of admixture with several pre-Bantu populations.
In this sense I find the following highlights:

Fig. S2 (annotated in green by Maju): CA plots based on haplogroup frequencies. Left: all the dataset, right: excluding outliers.

L3d and L3f founder effect:
The Himba and Herero, as well as the non-Bantu pastoralists Damara make one distinctive cluster defined by the high frequencies of haplogroup L3d, as well as L3f (not present among the Damara but found among the Kuvale). As discussed in the paper, the Himba and Herero may be related to the Kuvale of SW Angola but they have notable differential levels (or directionality) of aboriginal admixture. 
As both L3d and L3f are present in West and East Africa alike, it is interesting to track the specific subhaplogroups implicated in this founder effect, something done in fig. 4. 
The main L3d sublineage is L3d3a1, whose haplotype network shows a largely Khoisan centrality (not Damara) although this node is shared also by some unspecified “other Bantu”. The Southern Africa specificity of L3d3a was already noticed in the past (see here). So it is very possible that we are before an aboriginal Southern African lineage, maybe arrived with the first Khoisan Neolithic (or whatever other ancient flow) rather than a Bantu-specific founder effect. 
The main L3f subhaplogroup is L3f1b4a, which seems more specifically Bantu, with a major branch concentrated among the Himba, Herero and Kuvale. This lineage is not found among the Damara in spite of the other strong affinity of this Khoisan population towards the Himba and Herero. L3f1b is found in Southern Africa, Kenya and Oman (per Bihar 2008), so we are probably before a distinctive East African element, not too likely to be genuinely Bantu but possibly just assimilated into Bantu ethnic identity. 
Even if both lineages converge in the Himba and Herero, they are almost certainly different inputs, one of Damara (herder Khoisan) origin and the other of Bantuized East African origin maybe.
L1b founder effect:
L1b is essentially a West African lineage concentrated in the Sahel area from Chad westwards (although L1b1a2 is from the Nile basin). A particularly high frequency population are the Fulani pastoralists, original from the Westernmost African plateaus, who ruled many kingdoms in West Africa between the collapse of the colonial rule by Morocco and the consolidation of the European conquest of the continent.
As this study does not dwell in sublineages, we cannot understand the most likely specific origins of it among several Southern African populations, specifically the pooled NE Zambians (13%) and the Fwe and Shanjo of SW Zambia (24-27%).
In any case it is a notorious founder effect, almost absent in other Bantus of the area (0-10%).
Typical L0d Khoisan admixture:
This element is concentrated in Botswana (~25%) and with highest frequencies in the SW Kgalagadi (53%). It is also important among the Kuvale of SW Angola (21%). Other Bantu populations in this dataset have frequencies under 10%, some even zero. The Damara have 13%.
We know from previous studies that it is also found at high frequencies among the Xosha of South Africa (L0d3).
While L3h appears marked in the graph, the lineage is in fact absent in all populations except at very low frequency among the Kuvale (2%), so it does not seem actually of any relevance. 
Less typical L0k around SW Zambia:
While L0k is generally considered an aboriginal Southern African lineage it has a much more northernly distribution than the more common and surely older L0d. Its area of greatest commonality seems to be SW Zambia (see here and here).
This study confirms this distribution:

Supplementary Figure S3[A]: Haplogroup frequencies of important haplogroups in the populations studied here. A: Haplogroups L0d and L0k.(…)

The size of the circles is proportional to the sample size.

High frequencies of L1c (Pygmy admixture marker) among Southern African Bantus:
An interesting element is the commonality of L1c, typical of Western Pygmies and some other populations from Gabon (possibly representative of the wider West-Central Africa jungle region, not too well studied otherwise), among almost all Bantu populations in this dataset. 
The exceptions are the Herero, Himba, Kgalagadi and Tswana (0%), as well as the NE Zambians (4%). All the rest have frequencies between 12% and 30%. Even the non-Bantu Damaras have 11% of it.
In my understanding this almost certainly implies a notable level of admixture with Western Pygmies of the Bantus from especially Angola and West Zambia. A phenomenon that may be widespread in Central-West Africa. 
It is notable however that at least many of the populations with the highest likely Khoisan admixture (in its various forms, discussed in the previous sections) have the lesser frequencies of L1c (Pygmy admixture). So to a great extent these two aboriginal influences in Bantu mtDNA seem mutually exclusive and were probably produced after settlement rather than “on the march”. 
This in turn arises some interesting questions about the ethnic geography of Africa before the Bantu expansion. 

Update: I just noticed that Ethiohelix has parsed the haplogroups’ frequency into a very helpful chartLINK.

See also:
 

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.
 

New lactase persistence study rejects "calcium absorption" hypothesis

The “calcium absorption” hypothesis has been proposed as hypothetical mechanism to explain the apparent genetic sweep of lactose persistence alleles in Europe. According to this hypothesis, the possible role of milk in improved calcium absorption would counter the poor vitamin D synthesis in Northern Europe, preventing rickets.
However this hypothesis seems very weak, as I explained recently, notably because bone formation is only one of the various roles of vitamin D and it is probably much more crucial in correct brain development in childhood. Also there is another clear adaptation that actually solves the problem very well: whiter skin able to much more efficiently produce vitamin D in our bodies surfaces by mere exposition to sunlight, a trait that seems to have been increasingly favored after the Neolithic drop in fish consumption (the only actual nutritional source of vitamin D at relevant doses).
This new paper confirms my skepticism.
Oddný Ósk Sverrisdóttir et al., Direct estimates of natural selection in Iberia indicate calcium absorption was not the only driver of lactase persistence in Europe. MBE 2014. Pay per viewLINK  
[doi:10.1093/molbev/msu049]

Abstract


Lactase persistence (LP) is a genetically determined trait whereby the enzyme lactase is expressed throughout adult life. Lactase is necessary for the digestion of lactose – the main carbohydrate in milk – and its production is down-regulated after the weaning period in most humans and all other mammals studied. Several sources of evidence indicate that LP has evolved independently, in different parts of the world over the last 10,000 years, and has been subject to strong natural selection in dairying populations. In Europeans LP is strongly associated with, and probably caused by, a single C to T mutation 13,910bp upstream of the lactase (LCT) gene (-13,910*T). Despite a considerable body of research, the reasons why LP should provide such a strong selective advantage remains poorly understood. In this study we examine one of the most widely cited hypotheses for selection on LP – that fresh milk consumption supplements the poor vitamin D and calcium status of northern Europe’s early farmers (the calcium assimilation hypothesis). We do this by testing for natural selection on -13,910*T using ancient DNA data from the skeletal remains of eight late Neolithic Iberian individuals, whom we would not expect to have poor vitamin D and calcium status because of relatively high incident UVB-light levels. None of the 8 samples successfully typed in the study had the derived T-allele. In addition, we reanalyse published data from French Neolithic remains to both test for population continuity and further examine the evolution of LP in the region. Using simulations that accommodate genetic drift, natural selection, uncertainty in calibrated radiocarbon dates, and sampling error, we find that natural selection is still required to explain the observed increase in allele frequency. We conclude that the calcium assimilation hypothesis is insufficient to explain the spread of lactase persistence in Europe.

The study finds most likely that, most likely, there is population continuity between Neolithic farmers and modern local peoples in Northern Iberia and SE France. Technically they could only not reject this population continuity for all population parameters, but, considering that the same tests strongly reject it for Central Europe and Scandinavia, the most parsimonious conclusion is that some important population continuity does exist in SW Europe since Neolithic. In the words of the researchers:

It thus seems likely that population turnover since or shortly after the Neolithic transition has been less severe in southwestern Europe than in central or northern Europe.

However these ancient populations were lactose intolerant (rs4988235(C)) while modern ones in Northern Iberia are massively able to digest lactose (rs4988235(T)). This supports the theory of adaptive sweep for this allele. 
They suspect that the real reason behind the lactose persistence sweep is caused by basic nutritional reasons (calories and proteins) because milk may have been less subject to fluctuations in crops (traditionally cattle ate grass and not cereals, as happens in modern industrial production, while goats have even more varied natural food sources). In such circumstances episodic famines would have strongly favored lactose tolerant phenotypes, more so if lactose intolerant people would have drank milk or ate high-lactose dairies in desperation, causing them potentially deadly diarrhea.
This is not the same but fits well with my class structure hypothesis, outlined recently. The main reason why I favor this hypothesis is that this generalizing pattern should have affected farmers since very early in the Neolithic, even when they were still living in Asia or Greece, so it is very strange that the genetic sweep only appears since or after the Chalcolithic period, when a hierarchical class society is formed everywhere.

Correction: I wrongly reported the main European lactase persistence SNP as rs13910*T, when it is in fact rs4988235(T)
(already corrected in the text above) This was caused by the
nomenclature used in the Sverrisdóttir paper, where it refers to it as
-13910*T, which must be some other sort of naming convention. Thanks to Can for noticing.

See also:

 

Italian haploid genetics (second round)

More than a year ago I commented (as much as I could) on the study of Italian haploid genetics by Francesca Brisighelli et al. Sadly the study was published with several major errors in the figures, making it impossible to get anything straight. 
I know directly from the lead author that the team has been trying since then to get the paper corrected but this correction was once and again delayed by apparent inefficiency of PLoS ONE’s management, much to their frustration. Finally this week the correction has been published and the figures corrected.
So let’s give this study another chance:
Francesca Brisighelli et al., Uniparental Markers of Contemporary Italian Population Reveals Details on Its Pre-Roman Heritage. PLoS ONE 2012 (formally corrected in February 2014). Open accessLINK [doi:10.1371/journal.pone.0050794]
 
Notice please that you have to read the formal correction in order to access the new figures, the wrong ones are still in the paper as such. 
The corrected figures are central to the study:

Figure 1 (corrected). Map showing the location of the samples analyzed in the present study and those collected from the literature (see Table 1).
Pie
charts on the left display the distribution of mtDNA haplogroup
frequencies, and those on the right the Y-chromosome haplogroup
frequencies.

So now we know that the Northern mtDNA pie was duplicated in the original graph and that Central Italians are outstanding in R0(xH,V), which reaches 14% (probably most HV*), while they have some other peculiarities relative to their neighbors from North and South: some less U and no detected V. 
Other variations are more clinal: H decreases from North to South while J and T do the opposite.

Figure 3 (corrected). Phylogeny of Y-chromosome SNPs and haplogroup frequencies in different Italian populations.

In the Y-DNA side, the most obvious transition is between the high frequencies of R1b1a2-M269 (R1b3 in the paper) in the North versus much lower frequencies in the South. But also:
  • J2 is notorious in the Central region (and also the South) but rare in the North.
  • G frequencies in the South are double than those of Center and North.
  • The same happens with lesser intensity regarding E1b1b1-M35 (E3b in the study).
  • In contrast haplogroup I is most common in the North. However the Sardinian and sub-Pyrenean clade I2a1a-M26 (I1b2 in the paper), which is also the one documented in Chalcolithic Languedoc, is rare in all regions.

The study also deals with several isolated populations:

Figure 4. Haplogroup frequencies of Ladins, Grecani
Salentini and Lucera compared to the rest of the Italian populations
analyzed in the present study.

All them show large frequencies of mtDNA H relative to their regions. The Grecani Salentini do have some extra Y-DNA E1b1b1 (E3b) and J2, what may indeed underline their partial Greek origins. The Ladini show unusually high frequencies of R1b*(xR1b1a2) and K*(xR1a,R1b,L,T,N3), while the Lucerans are outstanding in their percentage of G.
I want to end this entry with a much needed scolding to the staff of PLoS ONE for their totally unacceptable original sloppiness and delay in the correction. And my personal thanks and appreciation to Francesca Brisighelli for her indefatigable persistence and enthusiasm for her work, which is no doubt of great interest.
 

Mitochondrial lineages from Myanmar

Myanmar, also known as Burma, has been one of those blind spots in the mapping of human genetics. Finally now we get to know something about the peoples of this SE Asian multiethnic state, although there are limitations because the sampling was performed among refugees in Thailand.
Monica Summerer et al., Large-scale mitochondrial DNA analysis in Southeast Asia reveals evolutionary effects of cultural isolation in the multi-ethnic population of Myanmar. BMC Evolutionary Biology 2014. Open accessLINK [doi:10.1186/1471-2148-14-17]

Abstract


Background


Myanmar is the largest country in mainland Southeast Asia with a population of 55 million people subdivided into more than 100 ethnic groups. Ruled by changing kingdoms and dynasties and lying on the trade route between India and China, Myanmar was influenced by numerous cultures. Since its independence from British occupation, tensions between the ruling Bamar and ethnic minorities increased.


Results


Our aim was to search for genetic footprints of Myanmar’s geographic, historic and sociocultural characteristics and to contribute to the picture of human colonization by describing and dating of new mitochondrial DNA (mtDNA) haplogroups. Therefore, we sequenced the mtDNA control region of 327 unrelated donors and the complete mitochondrial genome of 44 selected individuals according to highest quality standards.


Conclusion


Phylogenetic analyses of the entire mtDNA genomes uncovered eight new haplogroups and three unclassified basal M-lineages. The multi-ethnic population and the complex history of Myanmar were reflected in its mtDNA heterogeneity. Population genetic analyses of Burmese control region sequences combined with population data from neighboring countries revealed that the Myanmar haplogroup distribution showed a typical Southeast Asian pattern, but also Northeast Asian and Indian influences. The population structure of the extraordinarily diverse Bamar differed from that of the Karen people who displayed signs of genetic isolation. Migration analyses indicated a considerable genetic exchange with an overall positive migration balance from Myanmar to neighboring countries. Age estimates of the newly described haplogroups point to the existence of evolutionary windows where climatic and cultural changes gave rise to mitochondrial haplogroup diversification in Asia.

The main sampled ethnic group are the Karen, who live at the border with Thailand, but the Bamar or Burmans, the largest ethnic group, were also sampled in big numbers. 
Fig. 2.- Origin of samples and mitochondrial haplogroup distribution of Southeast Asian populations. Although most of the study participants originated from Karen State (red), a broad
sample spectrum from nearly all divisions and states of Myanmar (a) was included in this study. b shows the haplogroup distributions of populations from Myanmar and four other Southeast
Asian regions. In the white insert box the haplogroup heterogeneity of two ethnic
groups of Myanmar is illustrated. The hatched area in the map surrounding the border
between Myanmar and Thailand shows the main population area of the Karen people. The
Bamar represent the largest ethnic group (68%) in Myanmar. The size of the pie diagrams
corresponds to sample size.
The smaller samples are only detailed in the supplementary data for what I have seen, so I will not discuss them right now (maybe in an update?). 
Overall all SE Asians including the Southern Han from Hong-Kong appear similar in broad terms. Excepted Laos, this relative similitude is quite apparent in figure 3:
Fig. 3.- Multi-dimensional scaling plot of pairwise Fst-values and haplogroup distribution
of populations from Myanmar and 12 other Asian regions.
A distinct geographic pattern appeared in the multi-dimensional scaling plot (Stress = 0.086;
R2 = 0.970) of pairwise Fst-values: The Myanmar sample fitted very well within the Southeast
Asian cluster, the Central Asian populations formed a second cluster, the Korean sample
represented East Asia, the Afghanistan population was representative for South Asia
and Russia symbolized Western Eurasia. The main haplogroup distributions are displayed
as pie charts. The size of the pie diagrams corresponds to sample size. The proportion
of N-lineages (without A,B and R9’F) increases from very low percentages in Southeast
and East Asia over 50% in Central Asia to more than 75% in Afghanistan and 100% in
the sample of Russian origin. The proportion of the American founding haplogroups
A,B,C and D displayed an interesting pattern: from inexistent in Russians it increased
to more than 50% in East Asian Korea.
Looking at the particular differences in haplogroup frequencies, I’d say that the Thai are quite unremarkable, while the other populations show some peculiarities:
  • Karen: higher frequencies of R9/F, A, C and G
  • Bamar: much higher M* (and extremely diverse)
  • Laotian: higher frequencies of B and M7
  • Vietnamese: more B and N*
  • South Han (Hong-Kong): more D
It is very notable the high diversity of paragroup M* among the Bamar. The authors notice that not more than three individuals shared each different subhaplogroup, what points to a very high diversity within haplogroup M. I don’t have time right now to ponder the various lineages, some of which are newly described, but I probably will in the future, because, together with the high diversity in NE India, they have the potential of shifting the paradigm of Asian colonization by H. sapiens a bit towards the East.
The various M* and other novel haplogroups described in Myanmar is shown in fig. 4. Haplogroups M90 and M91 are new basal M sublineages, along with three other unnamed private lineages, which also appear as basal. Also M20a, M49a and G2b1a are new sublineages further downstream. Within N/R, another newly described lineage is B6a1.
The Bamar are extremely diverse not just within M*:

… the haplogroup composition of Bamar
was exceptionally diverse with 80 different haplogroups and a maximum of 6 samples
in the same haplogroup (Figure 4).

On the other hand, the Karen show the signs of genetic isolation instead, with large concentrations in the same haplogroups.
Interestingly, the authors think that rather than being a receiver, Myanmar was a major source of population to its neighbors:

Migration analyses of Myanmar and four Southeast Asian regions displayed a vivid exchange
of genetic material between the countries and demonstrated a strong outwards migration
of Myanmar to all analyzed neighboring regions (for details see Additional file 4: Table S4).

This influence is most intense to Laos, Thailand and South China, while things are more balanced regarding Vietnam instead.
 

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?
 

La Braña 1 carried the very rare Y-DNA haplogroup C (possibly C6-V20)

La Braña 1 without makeup
(Check for the updates below, please).

The late Epipaleolithic forager from NW Iberia (previously discussed here) had the patrilineal haplogroup C6, found so far only very rarely among modern Europeans (Scozzari 2012). This, I must say, I know by the moment only from secondary sources (Eurogenes, Dienekes and a personal communication) because I have not been able yet to put my hands on the relevant paper and this key detail is not mentioned in the abstract.

Iñigo Olalde et al., Derived immune and ancestral pigmentation alleles in a 7,000-year-old Mesolithic European. Nature 2014. Pay per viewLINK [doi:10.1038/nature12960]

freely available supplementary materials.


Abstract

Ancient genomic sequences have started to reveal the origin and the demographic impact of farmers from the Neolithic period spreading into Europe1, 2, 3. The adoption of farming, stock breeding and sedentary societies during the Neolithic may have resulted in adaptive changes in genes associated with immunity and diet4. However, the limited data available from earlier hunter-gatherers preclude an understanding of the selective processes associated with this crucial transition to agriculture in recent human evolution. Here we sequence an approximately 7,000-year-old Mesolithic skeleton discovered at the La Braña-Arintero site in León, Spain, to retrieve a complete pre-agricultural European human genome. Analysis of this genome in the context of other ancient samples suggests the existence of a common ancient genomic signature across western and central Eurasia from the Upper Paleolithic to the Mesolithic. The La Braña individual carries ancestral alleles in several skin pigmentation genes, suggesting that the light skin of modern Europeans was not yet ubiquitous in Mesolithic times. Moreover, we provide evidence that a significant number of derived, putatively adaptive variants associated with pathogen resistance in modern Europeans were already present in this hunter-gatherer.

Relevance for the overall understanding of macro-haplogroup C
Until the discovery of this C6 lineage, there were some strong reasons to suspect that Y-DNA C may have coalesced already in SE Asia or, at least, very close to it, with its subclades forming by pairs a three pointed star with geographical center in that area: C1 and C3 in NE Asia (and America), C2 and C4 in Wallacea and Australasia and C5 and some rather homogeneous C* in India.
The discovery of this C6 lineage and its confirmation as a Paleolithic one in Europe (i.e. not a “recent” arrival from somewhere else) add phylogenetic weight to the Western geography of haplogroup C, one of two main subdivisions of the main non-African Y-DNA lineage CF. However we cannot yet reach to conclusions about the “exact” origins of C because the macro-lineage still awaits improvement of its phylogenetic structure at the basal levels.
In plain language: it is quite likely that C2 and C4 form a monophyletic clade and I would not be surprised at all if C1 and C3 do the same. But then it is also possible that C5 and the Indian C* and/or the European C6 also form their own distinct branches. It is even possible that some of these lineages are related across subcontinental regions, as was recently found within MNOPS (aka K(xLT)). So we need first to know how they relate with each other a the top phylogenetic level before we can rush to any conclusion. In any case the discovery of C6 adds some preliminary weight to the hypothesis of C coalescing when still in South Asia.



Pigmentation genetics

There have been some rush to conclusions on the pigmentation of this and another Western European hunter-gatherer based only on genetics. I think that some of the conclusions are most likely incorrect, at least to some extent, because they are based on a SNP which only weights ~15% on skin coloration.

Judging on the figures (freely accessible, it seems), La Braña 1 carried two pigmentation alleles of gene SLC45A2 now rare among Europeans (but common elsewhere, i.e. the ancestral variant):

  • rs16891982, which affects hair color (7x chances of black hair among Europeans)
  • rs1426654, which affects skin pigmentation to some degree (correlated with skin color in Indians, irrelevant among modern Europeans because of fixation, weights only ~15% in Cape Verdeans’ skin coloration). 

Notice that while you can find online reconstructions that give La Braña 1 a very dark coloration, this is not necessarily the case at all but rather an oversimplistic  interpretation based only on one allele, allele that is not just dominant in West Asians and Europeans but also, for example, among Gujaratis, who are quite dark for European standards.

    It seems correct anyhow that this allele was only brought to Europe with Neolithic farmers (Stuttgart had it) but its alleged effect on pigmentation seems very much exaggerated.

    Fig. 4 from Beleza 2013 highlights that no single gene is decisive in skin pigmentation.

    It is probable anyhow that La Braña 1 had black hair.
    It is much more plausible that he had blue eyes because these are much more directly regulated by simple genetics.
    Continuity of immunity genetics
    La Braña 1 also had three immunity related alleles (derived variants) that have been retained at least to some extent by modern Europeans:
    • rs2745098 (PTX4)
    • rs11755393 (UHRF1BP1, related to lupus)
    • rs10421769 (GPATCH1)
    Comparison with global populations
    Fig. 5 (ED) offers various comparisons of La Braña 1 and Mal’ta 1 (from Siberia) with modern humans from around the World:

    Extended Data Figure 5: Pairwise outgroup f3 statistics.
    a, Sardinian versus Karitiana. b, Sardinian versus Han.
    c, La Braña 1 versus Mal’ta. d, Sardinian versus Mal’ta.
    e, La Braña 1 versus Karitiana. The solid line represents y = x.
    We can see in them that, La Braña 1 clusters well with modern Europeans, while Mal’ta instead strongly tends towards other Asians, often clustering with Pakistanis (“Central/South Asia” metapopulation).
    Maybe the most interesting graph is c, where we can see how the various populations deviate from the y=x line in the direction of La Braña (Europeans, West Asians) or Mal’ta (Native Americans particularly).
    Comparison with Neolithic samples and modern Europeans

    Extended Data Figure 4: Allele-sharing analysis.
    Each panel shows the allele-sharing of a particular Neolithic sample from refs 1 and 3 with La Braña 1 sample. The sample IDs are presented in the upper left of each panel (Ajv52, Ajv70, Ire8, Gok4 and Ötzi). In the upper right of each panel, the Pearson’s correlation coefficient is given with the associated P value.

    In all cases Swedes (SE), followed by Polish (PL), etc. share the greatest amount of alleles with La Braña 1, although I’m not sure if the differences are really that relevant (is really 69.3% significantly different from 68.7%?)
    In the vertical scale we can observe how the various populations tend more or less strongly towards various Neolithic samples (again with the same doubts about the significance of the differences). In the first row they are compared with Götland’s Pitted Ware individuals (of plausible Eastern European origins: strong cultural connections with Dniepr-Don Neolithic). Here Central Europeans show the greatest affinity with Ajv52 and Ajv70 (Basques Bulgarians also score high). There are some differences in the case of individual Ire8, whose closest modern relatives seem to be the Dutch. Swedes only score high re. Ajv52 but low to the others, while Finns score neutral-to-low relative to all them.
    The lower row compares with to mainstream Neolithic samples: Gok4 was a Megalithic farmer from SW Sweden and Ötzi was a Chalcolithic shepherd from Southern Tirol. The Swedish farmer is best approached by the Dutch, followed by various West-Central Europeans, while Basques Bulgarians, Finns and Swedes score low here. In the case of Ötzi nobody scores particularly high (some tendency in Switzerland and nearby areas), while Finns score clearly low.
    And that’s all I can say without direct access to the study. Enjoy.

    Update: I already got the paper (thanks again to the donor), I’ll see to update as need be once I have time to read it. Minor urgent edits above in red (and slashed out text).

    Update (Jan 29): The supplementary data is freely available (LINK) but I could not find it earlier. Almost all the information is in it, including a long list, much longer than mentioned above, of the SNPs found in La Braña 1, compared to various modern population frequencies. I don’t have time right now to dwell on it but I guess from a first read that I will have to amend some comments made on the issue of pigmentation above.

    Regarding the Y-DNA haplogroup, it is important to notice that its adscription withing haplogroup C seems very clear but its assignation to C6-V20 is more dubious because of the low quality of the genome. Only the V20 marker could be assigned, so the authors themselves are in doubt and wonder if it could alternatively be C* or C5, both with a South Asian affinity.

    In this sense I think it is worth noticing that the reference Y-DNA site ISOGG has recently revised the phylogeny of macro-haplogroup C and that they have already renamed C6-V20 as C1a2, making it a relative of the minor Japanese lineage earlier known as C1 (now renamed to C1a1), similarly South Asian C5-M356 has been renamed to C1b. So C1 is now perceived as a lineage that spans all Eurasia with an arguable South Asian centrality.

    Another (Papuan?) lineage once known as “C6” has long vanished from the phylogeny because of lack of plural samples, I understand.

     

    Is the ability to digest milk in Europeans caused by ancient social inequality?

    I’ve got involved these days in a discussion at Dienekes’ Anthropology Blog on the causes of lactase persistance (LP), i.e. the ability to digest milk as adults, in Europe. 
    The discussion orbits around a recent pay-per-view study by O.O. Sverrisdóttir, which claims, with some soundness for what I can discern, that LP in Europeans must have gone through positive selection. 
    Actually the study, as most of its kind, deals only with one LP marker, the well known SNP rs4988235, whose T variant allows adults (in dominant fashion) to digest milk, an ability often lost after weaning. 
    As I discussed back in 2010, there must be other such SNPs because actual LP phenotype only partly corresponds with the known LP alleles. But for whatever is worth, this is the (2010) “known allele” LP map:
    In Europe at least, it essentially corresponds with the T variant of rs49235, which concentrates in Scandinavia, Atlantic Islands and the Basque/SW French area. 
    At first I boarded the discussion with perplexity, because, even if the positive selection argument seems sound, it seems hard to find a reason for it: milk is not such a “great” source of food, excepting the issue of calcium and a high content of protein and fat, and the occasional claims that it is related to vitamin D deficiency seem extremely feeble because this vitamin is present at extremely low frequencies in natural milk, being rickets (where milk’s extra calcium could play some role) only a “less important” side effect of vitamin D deficiency, because its main harmful effect is to impair early brain development, a most serious problem for which calcium seems quite meaningless. So why would the ability to digest milk would have become such a matter of life or death to be actively selected for generation after generation until near-fixation?
    A key piece of information is that not a single sequenced Neolithic farmer has ever been found to carry the relevant LP allele (being all CC) and only since Chalcolithic we begin to find some TT and CT individuals. These are found in Sweden and in the southern areas of the Basque Country (see here for a lengthier discussion):
    • In Götland (Pitted Ware culture) only 1/20 alleles was T (i.e. 1/10
      persons had the CT combo, all the rest being CC and therefore likely
      lactose intolerants). 
    • In Longar (Navarre, dated to c. 4500 BP)
      1/7 individuals was TT, while the other six were CC (intolerant). There
      were no CT cases.
    • In San Juan Ante Porta Latinam (SJAPL, Araba, dated to c. 5000 BP), 4/19 were TT, 2/19 were CT, while the remaining 13 were CC.
    In the Basque cases we can appreciate that there must have already been two different populations regarding this SNP, because the CT cases are rare, implying that the two groups were only beginning to mix. It is worth mentioning that the Basque sites are odd in several aspects: on one side they seem to be military cemeteries (mostly males, arrow injuries and arrow points) and, on the other, they are rather exceptional in the Basque historical sequence of mtDNA pools (a lot more K and some other lineages than usual, less H and U).
    But a key finding in this study is that a Neolithic sequence from Atapuerca (near Burgos city, historical Basque SW border) was again CC for the relevant SNP (and therefore likely lactose intolerant). So it is very possible that proto-Basques did not have the T allele in notable frequencies either (although I keep some reservations for lack of larger samples).
    Whatever the case, if the T allele was selected positively as it seems, there must be a powerful reason for it. Was it cows, as some have claimed a bit too vehemently? I doubt it. 
    Why? Because for all we know from the Middle Ages, a period very similar in many aspects to the Metal Ages, it were goats and not cows the main providers of milk. This makes total sense because the hardy goats are rather inexpensive to rear, while cows are more costly and were often reserved for traction jobs. In most cases, cow produce, be it milk or meat, was an expensive luxury apt only for the upper echelons of a society that was becoming more and more hierarchical and unequal since precisely the Chalcolithic period. 
    Some oral accounts I have heard tell that not so long ago “acorn bread and goat milk” were often staple for the poor. In other areas maybe it was not acorn bread but, say, oat meal (or whatever else), but almost certainly the milk came almost invariably from goat udders, which very efficiently transform leaves and almost any vegetable, even thorny ones, into milk (and meat) for our consumption.
    It is crucial to understand that only if milk was a key survival staple, LP would have become fixated. Otherwise people would have preferred alternative foods and survived in similar shape, so positive selection would never have happened at this locus (non-LP individuals would have survived easily, selection would never have happened or would have been mild enough to retain much greater diversity). 
    It is also crucial to understand that, for all we know, this positive selection only happened since the Chalcolithic, i.e. when social stratification, inequality and private aristocratic property became common. Obviously the upper classes (or castes) had no problems accessing high quality foods, including meat, but the masses probably had growing problems in this aspect as the land and cattle became more and more concentrated in few hands. 
    Even where a wide class of free peasants existed, as was probably the case in much of Atlantic Europe, these were surely often not well-off enough to afford dairy cows. Instead goats would have been available for almost everybody, even the poorest of farmers. And very likely they were the only steady supply of proteins and fat, mostly via milk.
    Plausibly this need of extra nutrients of animal origin was more intense in the Atlantic areas of Europe because cereals do not perform so well in the prevalent humid conditions. Also before the medieval development of the heavy plough, the deep Atlantic soils were not at all as productive as they are now (and that’s why NW Europe only got its economic prominence in the last millennium, being before a peripheral area to the much more productive Mediterranean climate). 
    But climatic and agricultural issues aside, I strongly suspect that the main driver of LP positive selection, were goats, because these and their dairy produce were almost certainly available for almost everyone and, in the Metal Ages, the vast majority of people were farmers, often rather poor peasants who had to rely on their goats for survival, very especially in the bad times.
    I really do not see any other explanation that fits the data.

    PS- This social inequality & goats argument makes sense assuming that the positive selection theory is correct. However before I fully embrace it, I would need a half-decent sample of aDNA sequences from the Atlantic areas of Europe, notably Britain & Ireland, the Basque Country & SW France and mainland Scandinavia, where the T allele peaks. I say because what we find in some Chalcolithic sites, notably in the Basque Country, rather strongly suggests that there was already a TT population somewhere and we have not yet found it. So maybe some of the premises of the positive selection theory are not as sound as I said above – but we do not know yet.

     

    Andalusian mtDNA highlights W-E differences

    The issue of W-E genetic differences in Iberia has been discussed before in this blog by guest author Argiedude on the grounds of Y-DNA, showing that roughly the Western third of Iberia is distinct from the rest, most notably because of its higher presence of North African lineage E1b-M81. However the differences also appear in the mtDNA, even if they may be a bit more subtle because they cross with a N-S gradient of sorts.
    A new study focused on the matrilineages of two characteristic Andalusian provinces, Granada in the East and Huelva in the West, underscores that this difference is very real.
    Candela L. Hernández et al., Human maternal heritage in Andalusia (Spain): its composition reveals high internal complexity and distinctive influences of mtDNA haplogroups U6 and L in the western and eastern side of region. BMC Genetics 2014. Open accessLINK [doi:10.1186/1471-2156-15-11]

    Abstract (provisional)


    Background


    The archeology and history of the ancient Mediterranean have shown that this sea has been a permeable obstacle to human migration. Multiple cultural exchanges around the Mediterranean have taken place with presumably population admixtures. A gravitational territory of those migrations has been the Iberian Peninsula. Here we present a comprehensive analysis of the maternal gene pool, by means of control region sequencing and PCR-RFLP typing, of autochthonous Andalusians originating from the coastal provinces of Huelva and Granada, located respectively in the west and the east of the region.


    Results


    The mtDNA haplogroup composition of these two southern Spanish populations has revealed a wide spectrum of haplogroups from different geographical origins. The registered frequencies of Eurasian markers, together with the high incidence and diversification of African maternal lineages (15% of the total mitochondrial variability) among Huelva Andalusians when compared to its eastwards relatives of Granada and other Iberian populations, constitute relevant findings unknown up-to-date on the characteristics of mtDNA within Andalusia that testifies a female population substructure. Therefore, Andalusia must not be considered a single, unique population.


    Conclusions


    The maternal legacy among Andalusians reflects distinctive local histories, pointing out the role of the westernmost territory of Peninsular Spain as a noticeable recipient of multiple and diverse human migrations. The obtained results underline the necessity of further research on genetic relationships in both sides of the western Mediterranean, using carefully collected samples from autochthonous individuals. Many studies have focused on recent North African gene flow towards Iberia, yet scientific attention should be now directed to thoroughly study the introduction of European genes in northwest Africa across the sea, in order to determine its magnitude, timescale and methods, and to compare them to those terrestrial movements from eastern Africa and southwestern Asia. 

    Naturally the most noteworthy data is the frequency of mtDNA haplogroups in the two sampled populations:

    A map comparing this data with some other areas of Iberia (mostly the West) is also provided:

    Figure 3 – mtDNA haplogroup profiles registered in some populations of the Iberian Peninsula. The two Andalusian subpopulations studied here are marked with a red arrow. Codes are as in Additional file 3.
    What makes Onubenses (the inhabitants of Huelva, ancient Onuba, West Andalusia) peculiar in relation to their Granadino neighbors is their lower frequency of H (notably H*, H3 and H5), along with their higher frequencies of K1, U3a and several North African related haplogroups (U6, L1b and L2). The peculiarities of Granadinos (notably the high H5 frequency) are not so notable in comparison.
    Some of these Onubense peculiarities are reproduced in other parts of West Iberia, notably the low frequencies of H (but not at all in the NW corner), the presence of U6 (notably in North Portugal and also, not shown here, among the Maragatos of the León-Galicia border area) and to some extent the elevated frequency of K and some L(xM,N) lineages (varied localized frequencies).
    Much of this seems best explained by ancient flows from NW Africa (flows which may be Neolithic, Paleolithic or from the Metal Ages but hardly related to Phoenician or Muslim colonization, which had no W-E gradient whatsoever) but I have some qualms about the quick identification by the authors of the origins of Onubense high K1 in that area. At the very least it must be noticed that, unlike the other African markers, K1 is much more common towards the Eastern parts of NW Africa and is also found at similarly high frequencies in many parts of Europe, such as France and Central Europe.
    K1 was first spotted in Iberian ancient DNA in the early Neolithic (Los Cascajos, Navarre), and was an important Neolithic lineage through Europe. While I can’t discard the North African suggested origin, I think that other possibilities are at least as likely.
    On U6, the presence of the very rare U6c, one of two basal lineages of U6, only found previously in 5 Moroccans, 10 Canarians and in one Italian, reinforces the idea of U6 expanding from West to East (against what most conclusions suggest on the most unclear grounds) with a most likely Moroccan origin. In turn this raises the question on how pre-U6 arrived to Morocco, especially as the Aurignacoid Dabban industries now seem to never have gone further West than Cyrenaica, opening the possibility of this lineage having arrived to NW Africa via Europe, where we know that U in general was common in the Upper Paleolithic, and which clearly influenced North Africa at the Oranian (aka Iberomaurusian) cultural genesis (LGM) via Morocco (Taforalt and other sites).
    On the L(xM,N) lineages, it is worth mentioning that Cerezo 2012 claimed that some of them may be pre-Neolithic in Europe, especially L1b1a variants, which are widespread at low frequencies through Europe with an Iberian centrality.
    The overall picture is maybe best visualized by the Hierarchical Cluster Analysis:

    Figure 5 – Hierarchical Cluster Analysis (HCA) of 53 populations based on their mtDNAdiversity. The haplogroups used here are marked with arrows (vectors). Populations are indicated with numbers as in Additional file 3.
    Cluster 1 is particularly noticeable for its high frequency of mtDNA H, being composed by mostly Iberian samples (along with South Germans and some Sicilians). Granada, as well as nearby Córdoba, sit here (even if with a tendency towards the more mainstream European Cluster 2). Huelva is not too remarkable when compared with other European samples in the mtDNA HCA, although it does show some deviation towards NW Africa, clustering closest to Canarians.
    In spite of the good frequency of North African samples, it must be noted that the horizontal axis, in essence contrasting Europe vs. West Asia, has a weight of almost 50%, while the vertical axis, contrasting these two vs. North Africans (and the Sámi) only weights 13% (axis are almost never of the same relevance in PCA-like graphs, even if they are presented as such).
    In synthesis: NW Africa had some minor but significant genetic influence in the West Iberian third, long before the Muslim period, and this mtDNA study ratifies these distinctions in the particular case of Andalusia, adding some rich detail of data.
    Also, as the authors underline in their discussion, the issue of European genetic influence in North Africa still requires some serious investigation.
     
     

    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.