Razib Khan One-stop-shopping for all of my content

May 9, 2017

The Beaker is breaking!

The link is up, The Beaker Phenomenon And The Genomic Transformation Of Northwest Europe, but the paper is still processing:

I’ll update the post when I can read the paper.

September 18, 2011

The words of the father

Over at A Replicated Typo they are talking about a short paper in Science, Mother Tongue and Y Chromosomes. In it Peter Forster and Colin Renfrew observe that “A correlation is emerging that suggests language change in an already-populated region may require a minimum proportion of immigrant males, as reflected in Y-chromosome DNA types.” But there’s a catch: they don’t calculate a correlation in the paper. Rather, they’re making a descriptive verbal observation. This observation seems plausible on the face of it. In addition to the examples offered, one can add the Latin American case, where mestizo populations tend to have European Y chromosomal profiles and indigenous mtDNA.


In one of the more nuanced instances cited by Renfrew and Forster they note that though there is a fair penetration of both Austronesian mtDNA and Y chromosomes amongst Austronesian speaking inhabitants of New Guinea, Austronesian Y chromosomes are nearly absent from those populations which speak Papuan. In other words, the inference is that the native indigenous male elite perpetuated the Papuan language! I think the key issue here is social dominance, and the role of male cultural units. This is clear when you have a group like African Americans. Though mostly West African in ancestry this ethnic group clearly has ~20% European ancestry, mostly mediated through European males. This is simply a function of the social dominance of European males in relation to African males. And, it may be telling that African Americans are an English speaking Christian population, albeit with their own distinctive accent.

In the paper the authors note:

…It may be that during colonization episodes by emigrating agriculturalists, men generally outnumbered women in the pioneer colonizing groups and took wives from the local community. When the parents have different linguistic backgrounds, it may often be the language of the father that is dominant within the family group….

There is certainly some truth to this. But what I think that this narrative misses are the coarser and larger scale social units which expansive male cultural communities operate through. The spread of European males in Latin America was not uncoordinated. Often small groups of males decapitated indigenous male power elites, sometimes literally! Long distance travel, such as what the Austronesians engaged in, almost certainly must have entailed a minimal level of political and ideological commitment. They cite the example of the Genghis Khan haplotype, but that wasn’t perpetuated through a process of gradual demic expansion.

August 24, 2011

The geography of genes tells us only so much about history

Filed under: Historical Population Genetics,Human Genetics,Population genetics — Razib Khan @ 10:29 pm

L. L. Cavalli-Sforza’s The History and Geography of Human Genes is a book I reference a great deal. Cavalli-Sforza is the godfather of the field of historical population genetics, the phylogeography of humankind. Though his work was on classical autosomal markers, the huge literature which drew inferences from Y chromosomal and mtDNA variation followed in the wake of the The History and Geography of Human Genes. Spencer Wells, the director of the Genographic Project, alluded to Cavalli-Sforza’s influence in The Journey of Man. But at this point I think we have to be very careful of making inferences about the past from present patterns of genetic variation. This is made most stark by the fact that ancient DNA, which is a snapshot of the past, as opposed to an inference of it, sometimes diverges from our expectations based on present patterns of variation in surprising ways.


This to me is the big lesson to draw from a new paper in The Proceedings of the Royal Society B, The peopling of Europe and the cautionary tale of Y chromosome lineage R-M269. The results focus on two issues. First, the distribution ...

June 23, 2011

Celts to Anglo-Saxons, in light of updated assumptions

Over the past week there have been three posts which I’ve put up which are related. Two of them have a straightforward relation, Britons, English, Germans, and collective action and Britons, English, and Dutch. But the third might not seem related to the other two, We stand on the shoulders of cultural giants, but it is. When we talk about things such as the spread of language through “elite emulation” or “population replacement” they’re rather vague catchall terms. We don’t decompose them mechanistically into their components to explore whether they can explain what they purport to explain. Rather, we take these phenomena for granted in a very simplistic black box fashion. We know what they’re describing on the face of it. “We” here means people without a background in sociolinguistics, obviously.

To give an example of the pitfall of this method, in much of Rodney Stark’s work on sociology of religion (the production before his recent quasi-apologetic material) his thinking was crisp and logical, but the psychological models were intuitive and naive and tended to get little input from the latest findings in cognitive science. In One True God he actually offers an explanation for why ...

December 30, 2010

Are Turks acculturated Armenians?

To the left you see a zoom in of a PCA which Dienekes produced for a post, Structure in West Asian Indo-European groups. The focus of the post is the peculiar genetic relationship of Kurds, an Iranian-speaking people, with Iranians proper, as well as Armenians (Indo-European) and Turks (not Indo-European). As you can see in some ways the Kurds seem to be the outgroup population, and the correspondence between linguistic and genetic affinity is difficult to interpret. For those of you interested in historical population genetics this shouldn’t be that surprising. West Asia is characterized by of endogamy, language shift, and a great deal of sub and supra-national communal identity (in fact, national identity is often perceived to be weak here). A paper from the mid-2000s already suggested that western and eastern Iran were genetically very distinctive, perhaps due to the simple fact of geography: central Iran is extremely arid and relatively unpopulated in relation to the peripheries.

But this post isn’t about Kurds, rather, observe the very close relationship between Turks and Armenians on the PCA. The _D denotes Dodecad samples, those which Dienekes himself as collected. This affinity could easily be predicted by the basic parameters of physical geography. Armenians and Anatolian Turks were neighbors for nearly 1,000 years. Below is a map which shows the expanse of the ancient kingdom of Armenia:

Historic Armenia was centered around lake Van in what is today eastern Turkey. The modern Republic of Armenia is very much a rump, and an artifact of the historic expansion of the Russian Empire in the Caucasus at the expense of the Ottomans and Persians. Were it not for the Armenian genocide there may today have been more Armenians resident in Turkey than in the modern nation-state of Armenia,* just as there are more Azeri Turks in Iran than in Azerbaijan. Many areas once occupied by Armenians are now occupied by Kurds and Turks. But a bigger question is the ethnogenesis of the Anatolian Turkish population over the past 1,000 years.

Dienekes has already shed light on this topic earlier, adding the Greek and Cypriot populations to the mix as well as Turks and Armenians. The disjunction between Kurds and the Armenian-Turk clade suggests to us that Turks did not emerge out of the milieu of Iranian tribes in the uplands of southeast Anatolia and western Persia. Like the Armenians the Kurds are an antique population, claiming descent from the Medes, and referred to as Isaurians during the Roman and Byzantine period.

Below is a reformatted K = 15 run of ADMIXTURE with Eurasian population. I’ve removed the labels for the ancestral components, but included in populations which have a high fraction of a given ancestral component. The geographical labels are for obscure populations. I’ve underlined the four populations of interest:

First, let’s get out of the way the fact that Turkish samples have non-trivial, though minor, northeast Asian ancestry. The Yakut themselves are a Turkic group situated to the north of Mongolia. The more southerly and central Asian affinities the nomadic ancestors of the Anatolia Turks may have picked up in their sojourns over the centuries between their original homeland in east-central Siberia and Mongolia and West Asia. The rest of ancestry is rather typical of northern West Asian groups. In particular, Armenians! Here is the ancestral breakdown for the four groups I want to focus on using Dienekes’ labels:


Population Greek Cypriots Turks Armenians
West Asian 37.6 54.1 47.2 56.3
Central-South Asian 5.3 8.6 18.2 18.4
North European 25.1 5.6 12 12.3
South European 27.4 20.8 9.4 8.4
Arabian 3.4 8 4.3 3.4
Altaic 0.3 0 2.6 0.1
East Asian 0.3 0.2 2.2 0
Central Siberian 0.1 0.2 1.4 0.2
Chukchi 0 0 1.1 0.2
South Indian 0 0.1 0.8 0.3
Nganasan 0.1 0 0.4 0.2
Koryak 0.1 0 0.2 0.1
East African 0 0.4 0.1 0
West African 0 0 0.1 0
Northwest African 0.3 1.9 0.1 0

And now the correlations between the populations by ancestral components:



Greek Cypriots Turks Armenians
Greek * 0.863 0.823 0.813
Cypriots * * 0.941 0.946
Turks * * * 0.997
Armenians * * * *

Let’s remove the East Eurasian and African components, and recalculate the proportions by taking what remains as the denominator:


Population Greek Cypriots Turks Armenians
West Asian 38.1 55.7 51.8 57.0
Central-South Asian 5.4 8.9 20.0 18.6
North European 25.4 5.8 13.2 12.4
South European 27.7 21.4 10.3 8.5
Arabian 3.4 8.2 4.7 3.4

And the recomputed  correlations:



Greek Cypriots Turks Armenians
Greek * 0.747 0.640 0.647
Cypriots * * 0.901 0.908
Turks * * * 0.999
Armenians * * * *

With all the ~0 ancestral components which were common across these four populations removed the correlations have gone down. Except in the case of the Armenian-Turk pair, because I’ve removed the ancestries which differentiate them.

So what’s a plausible interpretation? A straightforward one would be that the Muslim Turk population of Anatolia has a strong bias toward having been assimilated Armenians, rather than Greeks. The cultural plasticity of Armenians in late antiquity and the early medieval period was clear: individuals of ethnic Armenian to origin rose the pinnacles of the status hierarchy of the Orthodox Christian Greek Byzantine Empire. The Macedonian dynasty of the Byzantines under which the civilization reached its mature peak were descended from Armenians who had resettled in Macedonia. Just as plausible to me is that eastern Anatolia as a whole exhibited little genetic difference between Greeks and Armenians, and the former were wholly assimilated or migrated, while the Armenians remained. One way to test this thesis would be type the descendants of Greeks who left eastern Anatolia during the population exchange between Greece and Turkey in the 1920s. But the difference between Greeks and Cypriots also points us to another possibility: perhaps the Greeks of Greece proper (as opposed to Anatolia) were much more strongly impacted by the arrival of Slavs? One need not necessarily rely solely on the Scalveni migrations either, water tends to be a major dampener to conventional isolation-by-distance gene flow, so the Greek mainland may always have been subject to more influence from the lands to the north.

Whatever the details of ethnogenesis may be, it will be interesting to see how things shake out as we increase sample sizes and get better population coverage. These results may be due to regional selection bias. One might expect that the descendants of Rumelian Turks be more “European” than Anatolian Turks. But, these data do seem to suggest on face value that Armenians are the population which Anatolian Turks have the most genetic affinity with.

* My main hesitation would be that Armenians are a very mobile population, and their numbers within a modern Turkey may have declined simply through emigration, just as those of Christian Arabs have over the 20th century.

December 20, 2010

Some of the Indo-Europeans found?

hunza
School girls in Hunza, Pakistan

A few days ago I observed that pseudonymous blogger Dienekes Pontikos seemed intent on throwing as much data and interpretation into the public domain via his Dodecad Ancestry Project as possible. What are the long term implications of this? I know that Dienekes has been cited in the academic literature, but it seems more plausible that this sort of project will simply distort the nature of academic investigation. Distort has negative connotations, but it need not be deleterious at all. Academic institutions have legal constraints on what data they can use and how they can use it (see why Genomes Unzipped started). Not so with Dienekes’ project. He began soliciting for data ~2 months ago, and Dodecad has already yielded a rich set of results (granted, it would not be possible without academically funded public domain software, such as ADMIXTURE). Even if researchers don’t cite his results (and no doubt some will), he’s reshaping the broader framework. In other words, he’s implicitly updating everyone’s priors. Sometimes it isn’t even a matter of new information, as much as putting a spotlight on information which was already there. Below is a slice of a bar plot from Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation. It uses STRUCTURE with K = 7. To the right of the STRUCTURE slice are two plots of individual data on French and French Basque from the same HGDP data set using ADMIXTURE at K = 10 from Dodecad.

fbasq


Repeated runs and higher K’s make it clear that the French Basque lack a “West Asian” aspect which other French, and Iberians as well, have. Some of this is clear in the paper I referenced above as well…the key is you have to look at the supplements at K = 6. Because the Basque are the only native non-Indo-European speakers in Western Europe, their origin and relationship to nearby populations has always been of interest (they also have the highest Rh- frequency of world populations). Granted, the French Basque are very similar genetically to the French as a whole. But, it is obviously highly informative that they lack an ancestral component in totality which seems to exist at low but consistent levels across Western European populations. The only other European population at K = 15 who lack the West Asian component in totality are Finns (the Lithuanians come very close).

This is all preamble to a discussion of a post Dienekes put up today, A solution to the problem of Indo-Aryan origins. Remember that Dienekes has been “playing” with ADMIXTURE for only a few months. To claim to have found a ‘solution’ to a problem as intellectually and politically intractable and explosive as this is rather bold. The crux of the matter is that at a certain confluences of K’s and population sets Dienekes has discovered a distinctive signature of ancestry which seems to be modal on the north slope of the Caucasus, and spans India and Europe. He terms this “Dagestani,” due to the fact that among a population sample from this province in Russia this ancestral component is overwhelmingly dominant. The patterns of Dagestani admixture in Europe and India are curious and suggestive.

1 – In Europe the frequencies are low, but irregularly distributed (excepting around the North Caucasus). Scandinavians and British have appreciable fractions, Finns and Southern Europeans do not. Here’s Dienekes:

Interpreting this pattern is not easy, but it does seem that this component seems to have a V-like distribution, achieving its maximum in Caucasus and its environs, then undergoing a diminution, and achieving a secondary (lower) frequency mode in NW Europe.

The surprising appearance of the homonymous Dagestan component in India suggests a widespread presence of a common ancestry element. The West Asian element, by comparison seems to have a more normal /\-like distribution around its center in Anatolia-Caucasus-Iran region. It does reach the Atlantic coast, but is lacking in Scandinavia and Finland, and also in India itself.

2 – South Indian Brahmins have appreciable fractions, but non-Brahmins in the same region do not. In contrast, those who come from Indo-Aryan speaking backgrounds do seem to have Dagestani ancestral components, irrespective of other aspects of ancestry. For example Pakistanis don’t have that much more Dagestani than South Indian Brahmins or Gujaratis. Also compare the relatively narrow window of Dagestani ancestry variance among Dodecad South Asians (I’m DOD075). DOD088 is from what I recall a Reddy from Andhara Pradesh, a non-Brahmin but non-low caste. It is interesting that they have a high proportion of “Pakistan,” but no Dagestani. I have ~10% Dagestani, but no Pakistani.

Below is K = 10 for a selection of populations. Dienekes has now included in two non-Indo-European speaking Pakistani populations: the Brahui (Dravidian) and Burusho (linguistic isolate in the mountains of Pakistan):
dages

Some general patterns are evident. The light blue is indicative of generic “Indian” ancestry. It is not found in appreciable proportions outside of subcontinental populations (or those of recent subcontinental origin). The same with the red, and light orange. For your reference the dark orange is a “Northern European” component, modal in Lithuania. The light and dark Green are both East Asian components. The dark blue is a “West Asian” component modal in Georgia, and prominent across Europe with declining as a function of distance from the eastern shore of the Black Sea (this is surely the West Asian which distinguishes the French from the French Basque). I believe that the light purple dominant in the Brahui and the light red dominant in the Burusho probably form as a compound the aforementioned Pakistani component. The dark purple is the Dagestani.

587px-Dravidische_SprachenFirst, a word on the Brahui. These are a group of tribes who reside in northern Balochistan in Pakistan. A small number are even to be found in Afghanistan. Historically they have had close relations with the Baloch, an Iranian speaking cluster of tribes who totally envelop the Brahui. The Brahui do speak a Dravidian language, of a family dominant in South India and found in isolated regions of Central and Eastern India. There are two broad models for the existence of a Dravidian language in Pakistan. The first is that the Brahui are remnants of more widely spoken Dravidian languages which date back to the Indus Valley civilization. The second is that the Brahui arrived during the medieval period from another region of South Asia where Dravidian languages were more common. Assuming either model, it has long been presumed that their involution by the Baloch has had a strong impact on the Brahui genetically; the two groups are very close. This is evident in Dienekes’ results as well. But observe that the Baloch are the group which seems more cosmopolitan in ancestry than the Brahui. If the Brahui were Dravidians from deep in India it seems that they would have a greater residual component of India-specific ancestry (light blue and orange). This is not so. In fact the Baloch have more of the Indian ancestral component than the Brahui. The Brahui component is found across Pakistan, and into India, albeit at lower proportions. Naturally, the Baloch have the second highest fraction. I believe these results should shift us toward the position that the Brahui are indigenous in relation to the Baloch, and that the Baloch ethnic identity emerged through the shift of a Brahui substrate, as evidenced by the greater cosmpolitanism of the Baloch. Additionally, Dienekes observes that the Brahui have a lower proportion of the Dagestani component than most other Pakistani groups, and several Indo-Aryan groups in India proper.

The Burusho are event more interesting than the Brahui. Unlike the Brahui the Burusho are very isolated in the mountainous fastness of Baltistan in northern Pakistan. Additionally, their language, Burushashki, is a linguistic isolate. Others of the class are Basque and Sumerian. In general it is assumed that linguistic isolates were once part of broader families of languages which have gone extinct. Burushashki probably persists in large part because of the geography which its speakers inhabit. Mountainous areas often preserve ethnic and linguistic diversity because the terrain allows for the persistence of local variety. I believe it is plausible that the Burusho have been far more isolated than the Brahui. This seems to show up in the ADMIXTURE plot, the Burusho have a greater proportion of their modal ancestral component than the Brahui. Additionally, the Burusho have even an smaller component of Dagestani than the Brahui.

Below is a chart Dienekes constructed ordered by proportion of Dagestani for his South Asian populations. Next to it I’ve placed a chart from a PCA which has some of the same population samples. Compare & contrast:

pcadag

The PCA is looking at between population variation in totality. So naturally the Dagestani component isn’t going to be predictive of that. Rather, it speaks to the possibility which Dienekes is mooting: that the Dagestani component spread in the India subcontinent with the Indo-Aryans specifically, overlying the local resident substrate. In South India this meant that Brahmins brought this, mixing with the indigenous Dravidian population. In Pakistan the Indo-Aryan, and Iranians, were overlain on a substrate which were the ancestors of the Burusho and Brahui. The dominant signal of genetic relationship has to do with the substrate, not the Indo-Aryans. So that’s what’s going to show up on the PCA. In other PCA plots the model where South Indian Brahmins are a linear combination of a Pakistani-like population and a Dravidian population becomes clearer. But when you look at ancestry using something like ADMIXTURE you have the potential to tease apart different components, and so uncover relationships which may have been obscured when looking at aggregate variation.

dieDienekes’ model seems to post three steps in rapid succession ~4,000 years ago. A background variable which must be mentioned is that one must account for the Mitanni, a dominant Syrian power circa 1500 BC where a non-Indo-European language was the lingua franca, and yet a definite Indo-Aryan element existed within the elite. Indo-Aryan specifically because the Indo-European element within the Mitanni was not Iranian, but specifically Indo-Aryan. An easy explanation for this is that the Indo-Aryan component of the Indo-Iranian branch of the Indo-European languages crystallized outside South Asia, and independently reached Syria and India. In Syria it went extinct, while in India it obviously did not. By Dienekes’ model the Mitanni would be rather closer to the urheimat of the Indo-Aryans.

An aspect of his model which I do not understand is why it has to be Indo-Aryan, instead of Indo-Iranian. The South Asian population which the Dagestani component is modal, the Pathans, are Iranian, not Indo-Aryan. Additionally, this model seems to not speak in detail to the existence of the Dagestani element among Europeans. Here is a sorting of European populations (with Iranians included) by the Dagestani component:


Population Dagestan
Urkarah 93
Lezgins 47.9
Stalskoe 38.7
Adygei 16.4
Orcadian (Orkney) 12.6
Georgians 12.4
White_Utahns 11.2
Iranian 10.9
Scandinavian_D 10.2
Armenian_D 9.9
German_D 9.1
Turks 8.8
Armenians 8.4
French 7.9
Hungarians 7.5
Russian_D 6.3
Spanish_D 4.6
North_Italian 4.5
Spaniards 4.4
Romanian 4.1
Finnish_D 4.1
Russian 4
Greek_D 3.8
Portuguese_D 3.6
Tuscan 3.5
Tuscans 3.4
Lithuanians 2.9
S_Italian_Sicilian_D 2.8
Belorussian 2.5
Cypriots 2
Sardinian 1.5
French_Basque 0.7

There is here a strange pattern of rapid drop off from the Caucasus, and a bounce back very far away, on the margins of Germanic Northwestern Europe. This to me indicates some sort of leapfrog dynamic. A well known illustration of this would be the Ugric languages. The existence of Hungarian on what was Roman Pannonia is a function of the mobility and power of Magyar horseman, and their cultural domination over the Romance and Slavic speaking peasantry (their genetic impact seems to have been slight). No one believes that Germanic languages are closely related to Indo-Aryan (rather, if there is structure in Indo-European beyond Indo-Iranian, Celtic, etc., it would place the Indo-Iranian languages with Slavic). So what’s going on? I think perhaps the Dagestani component is part a reflection of the common Indo-European origin in that region. For whatever reason that signal is diminished in much of the rest of Europe. Perhaps Southern Europe was much more densely populated when the Indo-Europeans arrived. Additionally, it seems highly likely that in places like Sardinia, much of Spain, and Cyprus, Indo-European speech came through cultural diffusion (elite emulation) and not population movement. Or perhaps we’re seeing the vague shadows of population admixtures on the Pontic steppe, where distinct Germanic and Indo-Iranian confederations admixed with a common North Caucasian substrate.

Going back to India, let’s revisit the model of a two-way admixture between “Ancestral North Indians,” who were genetically similar to Europeans and West Asians, and “Ancestral South Indians,” who were closer to, but not very close to, East Eurasians. The ANI & ASI. The ASI were probably one of the ancient populations along the fringe of southern Eurasia, all of whom have been submerged by demographic movements from other parts of Eurasia over the past 10,000 years, excepting a few groups such as the Andaman Islanders and some Southeast Asian tribes. The model was admittedly a simplification. But taking that model as a given, and accepting that the Dagestani element is in indeed Indo-Aryan, we can infer that the ANI were not Indo-European. It is notable that the South Indian Brahmins have elevated fractions of both the Brahui and Burusho modal components. This is probably indicative of admixture of the Indo-Aryan element in the Indus Valley, prior to their expansion to other parts of India. I assume one of the languages spoken was Dravidian, though if ancient Mesopotamia was linguistically polyglot at the dawn of history I would not be surprised if the much more geographically Indus Valley civilization was as well.

arai
Aishwarya Rai

The irony is that today when someone refers to a “Dravidian” physical type, they’re not talking about someone who looks like a Pakistani. They’re talking about someone who looks South Indian, where most Dravidian languages are spoken. But combining the inference from Dienekes’ model and the previous two-way admixture model, you reach the conclusion that lighter skin and more West Asian features among South Asians may be more due to Dravidian-speaking ancestors in the Indus Valley, not Indo-Aryans! It goes to show the wisdom of differentiating linguistic classes from biological ones when discussing historical population genetics. Unfortunately wisdom most of us interested in these topics do not show, alas.

As I like to say, interesting times….

Note: If you leave a comment, please don’t be smarter-than-thou in your tone. I have stopped publishing those sorts of comments because the reality is that most of them have not been that smart or informed. At least by my estimation. If you actually are smarter than the average-bear, and impress me with your erudition and analysis clarity, I’ll probably let your comment through no matter your attitude. But I wouldn’t bet on it if I were you, so show some class and humility. Most of us are muddling through.

Image Credit: Georges Biard, iStockPhoto

September 28, 2010

On the varieties of Roma

Filed under: Genetics,Genomics,Gypsies,Historical Population Genetics,Roma — Razib Khan @ 12:05 am

Dienekes has a pointer to a new paper on Gypsy genetics which surveys Y lineage variation among three Roma groups from Serbia in the context of Europe-wide Gypsy genetic variance, as well as their potential host (European) and source (Indian) populations. Since I recently posted on the topic, and Dienekes didn’t post some of the figures, I thought I’d do so. In particular here’s the MDS of the Gypsy groups in the international context:

romaY

Remember that that’s just the Y chromosomes, the male lineages. There are some broad affinities, but note how scattered the Gypsy groups are. I assume that’s an artifact of large shifts in Y lineage frequencies because of genetic drift through bottlenecks. Additionally, the Vojvodina Roma group which was surveyed specifically in this study is a definite outlier (VOJ). As I stated above they typed three Roma groups from Serbia. They were resident in Kosovo, Belgrade and Vojvodina (which is north of Belgrade, near Hungary). They calculated admixture estimates for the three groups based on their Y haplogroup proportions, and found that ~100% of the male line ancestry of the Kosovo Roma was South Asian, ~75% of the Belgrade Roma was South Asian, but ~0% of the Vojvodina Roma sample had South Asian male ancestry. For what it’s worth, they estimate that the balance of the Belgrade Roma ancestry was Slavic European (based on the frequency of the given haplogroups in regions and ethno-linguistic groups of Europe), while the Vovjodina Roma had all non-Slavic ancestry. The Vovjodina Roma men overwhelmingly carry a variant of haplogroup E1b1b1a2. Here’s the frequency map from Wikipedia:

800px-HgE1b1b1a2

Since they’re Kosovo Roma, and they seem to be a subclade of a lineage at high frequency among Albanians, it stands to reason that at some point in history a group of Albanian men, or a Albanian man, was culturally assimilated into a Roma identity. From the earlier charts I posted using variation on autosomal loci, instead of just a uniparental lineage, that shouldn’t be too surprising. The interesting point, as Dienekes noted, is that despite the genetic variation the Roma are surprisingly similar culturally across Europe. In particular it is striking that they tend to continue speaking an Indo-Aryan language. It’s not like this is unprecedented though. Some commenters have already observed striking analogies between Gypsies and Jews genetically and culturally, or at least in terms of the ethnogenesis of both groups as genetic and cultural compounds on the European scene. The analogy is tight enough that you have papers such as Multiple Origins of Ashkenazi Levites: Y Chromosome Evidence for Both Near Eastern and European Ancestries, which I believe will be recapitulated for the Gypsies broadly, and even the particular subset who are termed Roma.

Image Credit: Wikimedia Commons

September 17, 2010

Of Iran, Turan, and Turks

uzbekmanThere’s a new paper out in The European Journal of Human Genetics which is of great interest because it surveys the genetic and linguistic affinities of two dozen ethno-linguistic groups from the three Central Asian nations of Uzbekistan, Kyrgyzstan, and Tajikistan. This is what the Greeks referred to as Transoxiana, and the Persians as Turan. Originally inhabited by peoples with close cultural affinities with those of Persia, indeed, likely the root of the peoples of Persia, by the historical period Turan developed a distinctive identity as a frontier or march. It was in Turan where the Turk met the Iranian (a class which included non-Persian groups, such as the Sogdians), from the pre-Islamic Sassanians down to the present day. It is a region of the world which has a very ancient urban culture, cities such as Merv, as well as peoples that were only recently nomads, forcibly made sedentary by the Soviet regime.

To add another twist to the picture many of the ethno-linguistic groups which we are familiar with today and which serve as the cores of the new Central Asian nations only came into being within the last few centuries, with a particular “push” from Russian Imperial and Soviet ethnologists who were tasked with fleshing out national identities with which the center could negotiate. A “Tajik” is after all simply part of the Persian-speaking residual population of Central Asia, spreading down into Afghanistan. The carving out of an independent Tajikistan out of the Central Asian landscape is as much a creation of the modern age as the state of Israel. The “Uzbek” identity was once simply that of the ruling caste of Transoxiana who came to power after the decline of the Timurids. Today it is an appellation which brackets the settled Turkic speaking peoples of Uzbekistan and beyond.

ResearchBlogging.orgInto this near Gordian knot of history and ideology walk the naive and well-meaning geneticists. There is no great objection one can make to the genetics within the paper, but the historical framework and some of the assertions are peculiar and tendentious indeed. It’s a problem which starts within the abstract. In the heartland of Eurasia: the multilocus genetic landscape of Central Asian populations:

Located in the Eurasian heartland, Central Asia has played a major role in both the early spread of modern humans out of Africa and the more recent settlements of differentiated populations across Eurasia. A detailed knowledge of the peopling in this vast region would therefore greatly improve our understanding of range expansions, colonizations and recurrent migrations, including the impact of the historical expansion of eastern nomadic groups that occurred in Central Asia. However, despite its presumable importance, little is known about the level and the distribution of genetic variation in this region. We genotyped 26 Indo-Iranian- and Turkic-speaking populations, belonging to six different ethnic groups, at 27 autosomal microsatellite loci. The analysis of genetic variation reveals that Central Asian diversity is mainly shaped by linguistic affiliation, with Turkic-speaking populations forming a cluster more closely related to East-Asian populations and Indo-Iranian speakers forming a cluster closer to Western Eurasians. The scattered position of Uzbeks across Turkic- and Indo-Iranian-speaking populations may reflect their origins from the union of different tribes. We propose that the complex genetic landscape of Central Asian populations results from the movements of eastern, Turkic-speaking groups during historical times, into a long-lasting group of settled populations, which may be represented nowadays by Tajiks and Turkmen. Contrary to what is generally thought, our results suggest that the recurrent expansions of eastern nomadic groups did not result in the complete replacement of local populations, but rather into partial admixture.

In my initial comment on this paper in a link round-up I wondered what the authors were thinking making such a comment: anyone who knows Central Asians would see on their faces that the Turks did not completely replace the local populations. The image above is of an Uzbek man, who does not exhibit any visible “Mongolian” features. This is not the norm, but is not unheard of. Even populations which are presumed to have less Iranian admixture, such as the Kazakhs, exhibit a range of physical types. It would be one thing if this reference was an isolated peculiarity, but there are other comments within the paper which indicate to me that the research group’s familiarity with the non-genetic literature is cursory at best. They refer to Huns as having “brought the East-Asian anthropological phenotype to Central Asia.” There is no clear definite foundation for this assertion. Unfortunately historians do not have a clear idea what the ethno-linguistic character of the Huns was. By the time Roman observers encountered them the Hunnic horde seems to have been predominantly German, with a Iranian (Alan) secondary component, the Huns themselves being a small elite (Attila’s name itself may be Gothic). In light of subsequent eruptions into Europe of Turkic and Ugric nomads it is easy to slot the Huns into this exotic category, but the primary literature makes it clear that you can’t ascertain their ethnic character from the contemporary sources (the “White Huns” of Central and South Asia had no real connection to the Huns of Europe).

Near the end of the paper they say something really peculiar: “The Westernized view of westward invasions usually emphasizes the extreme violence and cruelty of the hordes led by Attila the Hun (AD 406–453), or that from the Mongolian empire led by Genghis Khan. However, our results somehow challenge this view and rather suggest that these more recent expansions did not lead to the massacre and complete replacement of the locally settled populations….” It is true that European observers of the Mongol expansion did not have a sanguine attitude. But the idea that Mongols were genocidal exterminationists really comes to us via the Islamic historians, for whom the Mongol conquests were totally shocking and a literal world-turned-upside-down moment. The Mongol conquests did seem to result in a decline in population between Mesopotamia and Transoxiana. Whole cities in Central Asia were depopulated. There is an assumption that the Mongol conquests marks the turning point where Central Asia passed from being a predominantly Iranian world with a Turkic military elite (which was to be the nature of Iran proper until the 20th century) to a Turkic world with a large Persian minority. Though the military conquests of the Mongols were important punctuating events, I do not believe that scholars today would assume that they produced an ethnic shift in toto. On the contrary, the null hypothesis is generally against migrationism.

With those preliminaries out of the way, what’s going on with the genetics? Below are the less interesting tables & figures. The first is important because it has the abbreviations which they use. Basically anything that starts with a “T” are Indo-Iranian Tajiks, and everything else is Turkic, except LUzn LUza, who are Indo-Iranian Uzbek nationals, but I presume would be ethnic Tajiks in Uzbekistan (this stuff is really confusing in regards to labels, because as I said the national categories are to some extent ad hoc impositions on more ancient identities which don’t always follow the European language = nation formula). The second image is a figure which shows the sampling of locations, as well as pie charts with ancestral quanta. The third image is a table which shows that Indo-Iranians are genetically more varied than Turks. While the fourth is a STRUCTURE plot which I reedited to zoom in on peoples of interest for this study, as well removing some of the lower K’s. Remember that each K is a putative ancestral population. As Dienekes notes since they used only 27 microsatellite markers across their 26 populations, the plot may inflate minor ancestral contributions.

Of more interest is the correspondence analysis, which is conceptually similar to principal component analysis. The variate inputs are allele counts. I’ve obviously reedited the figure a bit, and added some labels (yeah, I ended up thinking that rotating after I’d added some labels was best, sorry). Note the clear color-coding of Turkic vs. Iranian Central Asian groups.

turkiraneurasian

There’s a clear separation linguistically between Iranian speaking and Turkic speaking groups in Central Asia. Some of the Turkic groups are close to Iranian groups, closer than to other Turkic groups, but still the two broad sets have a coherent identity. Undergirding the linguistic variation is classical geographic variation. The eastern Turkic groups seem the least impacted by the Iranian substrate which was dominant before the arrival of Turks, while the Turcoman group sampled from western Uzbekistan seems to have been the most genetically “Iranized.” In a world wide context the central position of Central Asians is not surprising. Interestingly the Iranian groups of Central Asia seem to overlap rather well with the Indo-Iranian groups from the HGDP data set. In contrast, the Turkic groups are distributed along a linear axis from East Asians to the Iranian cluster. This is the same pattern evident among African Americans as individuals. It’s a two-way admixture, with different dosage degrees by population as a function of history and geography (I presume you’d see the same pattern if it was broken down on individuals with a SNP-chip).

admixMoving to the explicit admixture estimates, the labels leave something to be desired. The shaded area is for Turkic speakers. The very last group, TJY, indicates the Yagnobis of Dushanbe. I happen to know offhand that the Yagnobis are reputed to be descendants of the Sogdians, having preserved their language and Zoroastrian religion relatively late in history before switching to Tajik and Islam. Like many ethno-linguistic relics these people preserved their independent identity after the Arab conquest, which saw the decline of Sogdian influence on the Silk Road, by taking refuge in isolated regions. It is no surprise then that this group shows the least East Asian admixture of all the Iranian samples, as they were isolated from many of the social and historical processes which were operative in Transoxiana after the conquest by the Arabs, and the later pushing in of the zone of Turkic hegemony after the fall of the Samanids.

These admixture estimates definitely put the spotlight on the role of Central Asia as a nexus of sorts. In the archaeology and history it is clear that Central Asia has been affected by peoples of European, South Asian, Middle Eastern, and East Asian origin. Central Asia itself has been the mother of empires, famously the seat of Timur, but also the original base of what later became the Abbasid dynasty. At one point the Caliphate was split between western and eastern factions and there was a possibility that the capital would be relocated from Baghdad to the Central Asian city of Merv! I do not believe that the Arabs had a strong genetic impact, nor was there a large South Asian migration in recent periods into Central Asia. So the admixture estimates adduced for these groups may be due to the natural cline in allele frequencies which are found in different peripheral Eurasian populations. Frequencies which are naturally intermediate in Central Asia. The main caveat is that it is probable that local conditions will vary a great deal. In contrast we have strong reason to suspect that the East Asian component arrived relatively recently with the Turks, and we see that its aspect is most evident among the groups which were nomadic within living memory, the Kazakhs and Kyrgyz. These two ethnicities, which are really compounds of several tribes or “hordes,” were only marginally integrated into sedentary Islamic society where the Tajik element would be prominent (shamanism among many of these tribes only disappeared under the influence of the Islamic missionaries sponsored by Russian Empire). I think this pattern is reinforced by what we saw in the correspondence analysis, where the Turkic groups exhibited a linear distribution toward East Asia, while the Iranian ones were placed where you’d expect them geographically. Finally, I want to note that Dienekes observes that using South Asians as a Central Asian population source is strange since South Asia is more appropriately thought of as a demographic sink for Turan. True, but the HGDP populations are strongly biased toward groups with relatively little indigenous South Asian ancestry, with the Sindhi being the only Indo-Aryan speakers within the set. So I think that objection is mitigated by these factors. Rather, the Iranian-speaking Pakistani groups serve as proxies for the original Central Asian Iranian substrate, from which both they and the Tajiks presumably derive.

Moving back to the Turk vs. Iranian distinction, the authors note that the Turkic groups exhibit a strong degree of genetic homogeneity on the Y chromosomal lineages. This points to the possible manner in which the East Asian genetic element spread in Central Asia, not necessarily just through population displacement, but also through polygamy and the high reproductive fitness of particular “super-male” lineages. The children of elite Turkic men who took Iranian wives presumably adopted the culture of their fathers, including the linguistic identity. This may have been particularly easy in Central Asia because they did not have to repudiate their maternal heritage in totality, as Persian culture still had great status and currency. If we partition the ancestry into “East Eurasian” and “West Eurasian” components the Turkic groups have much more of the latter than the Iranian ones have of the former. That stands to reason as the Turks were newcomers, and an elite which the locals would wish to assimilate to if they had the opportunity. In contrast, the shift from Turk to Iranian may have been rarer, and a switch which individuals would wish to avoid since the latter did not have the same level of temporal power. Over ~1,500 years gene flow does occur between the groups, and even the Yagnobis have appreciable East Asian ancestry. Eventually the linguistic differences would probably be dwarfed by the geographical ones, but currently we’re taking a snapshot of a “transient.”

It’s complicated. And one has to be very careful about using terms like “Turk” in a localized context, vs. a more international one. The Turks of Turkey are overwhelming derived from the same source populations as their Balkan (because of Rumelian Turks), Iranian, and Armenian, neighbors. The decline in East Asian fraction is evident even in this sample, as the Turcomans from western Uzbekistan have the least eastern ancestry of any of the groups. But this paper is an excellent within into a critical geographical hinge of genetic variation and historical tumult (though one must set aside some of their tacked-on historical speculations).

Citation: Martínez-Cruz B, Vitalis R, Ségurel L, Austerlitz F, Georges M, Théry S, Quintana-Murci L, Hegay T, Aldashev A, Nasyrova F, & Heyer E (2010). In the heartland of Eurasia: the multilocus genetic landscape of Central Asian populations. European journal of human genetics : EJHG PMID: 20823912

Image Credit: Wikimedia

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