November 10, 2012

Mitochondrial snapshots from an East-West encounter in Altai

Ukok Plateau landscape
(CC by Kobsev)
The Iron Age Pazyryk culture of Ukok Plateau (Altai Mountains, Central Asia) are generally considered to be related to Scythians or other Indoeuropean peoples of Western affinity. However the affiliation of Pazyryk peoples remains controversial. A new Catalan study may help to shed some light to the matter:

Mercedes González Ruiz et al., Tracing the Origin of the East-West Population Admixture in the Altai Region (Central Asia). PLoS ONE, 2012. Open access ··> LINK [doi:10.1371/journal.pone.0048904]

Abstract

A recent discovery of Iron Age burials (Pazyryk culture) in the Altai Mountains of Mongolia may shed light on the mode and tempo of the generation of the current genetic east-west population admixture in Central Asia. Studies on ancient mitochondrial DNA of this region suggest that the Altai Mountains played the role of a geographical barrier between West and East Eurasian lineages until the beginning of the Iron Age. After the 7th century BC, coinciding with Scythian expansion across the Eurasian steppes, a gradual influx of East Eurasian sequences in Western steppes is detected. However, the underlying events behind the genetic admixture in Altai during the Iron Age are still unresolved: 1) whether it was a result of migratory events (eastward firstly, westward secondly), or 2) whether it was a result of a local demographic expansion in a ‘contact zone’ between European and East Asian people. In the present work, we analyzed the mitochondrial DNA lineages in human remains from Bronze and Iron Age burials of Mongolian Altai. Here we present support to the hypothesis that the gene pool of Iron Age inhabitants of Mongolian Altai was similar to that of western Iron Age Altaians (Russia and Kazakhstan). Thus, this people not only shared the same culture (Pazyryk), but also shared the same genetic east-west population admixture. In turn, Pazyryks appear to have a similar gene pool that current Altaians. Our results further show that Iron Age Altaians displayed mitochondrial lineages already present around Altai region before the Iron Age. This would provide support for a demographic expansion of local people of Altai instead of westward or eastward migratory events, as the demographic event behind the high population genetic admixture and diversity in Central Asia.

Surely the most interesting finding of this study is that, unlike all other studies so far in the area, Bronze Age burials¹ from westernmost Mongolia carried 100% (3/3) Eastern Asian haplogroups (all D). Only one sample from the same wider region and period had ever before produced some Eastern lineages but as minority (9%, Southern Siberia, Turbat 2005), all others producing instead 100% Western haplogroups.

Instead Iron Age burials produced a much more mixed picture (n=16):
  • Eastern haplogroups: 8 (50%)
    • A: 1
    • C: 2
    • D: 4
    • G2a: 1
  • Western haplogroups: 8 (50%)
    • HV6: 1
    • J: 1
    • K: 3
    • U5a1: 2
    • T1: 1
This process however does not just imply penetration of Western lineages in the Mongolian part of Altai but also, as can be inferred in other studies' data, an extension of Oriental ones to the Western parts of Central Asia. The contrast between a well defined East-West genetic divide in the Bronze period and almost total blur in the Iron one instead is dramatically captured by these maps:

Figure 2. Spatial frequency distribution maps of East Eurasian lineages.
A- Pre-Iron Age period; B- Iron Age period. Frequency values and detailed information for populations 1–8 are shown in table 3. 1- Mongolia (Altai), 2- Gorny Altai, 3- West Kazakhstan, 4- Central Kazakhstan, 5- South Kazakhstan, 6- East Kazakhstan, 7- SW Siberia, 8- Mongolia (Egyin Gol).

The authors conclude:
The Pazyryk groups analysed so far appear to be genetically homogeneous and they did not present significant genetic differences to current Altaians. These results suggest that roots of the current genetic diversity and admixture of the Altai region in Central Asia could be traced back to the Iron Age.

______________

Note: 

¹ Text minimally edited long after original publication because the Bronze Age burials from the region do not belong to Pazyryk culture (which only spans part of the Iron Age), as I wrongly said first.

10 comments:

  1. I wonder to which culture or cultures their Bronze Age samples belong and what are their associated dates?

    The mtDNA of the Xiaohe mummies was found to be mostly haplogroup C, with some H and K, while all paternal lines were R1a1a. This seems to indicate that an east-west admixed population was already present in the Tarim Basin during the Bronze Age. Given that archaeological reports suggest that the Altay Mountains were not a cultural barrier during the Bronze Age, I'm thinking that perhaps three samples from that era are a weak basis for claiming, "that the Altai Mountains played the role of a geographical barrier between West and East Eurasian lineages until the beginning of the Iron Age".

    I think it's more accurate to simply claim that massive, east-west, demic expansion is an Iron Age phenomenon. In which case, this is a nice confirmation of something we already knew.

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    1. I understand that they are from early Pazyryk. I know only so much on that but when reading Wikipedia, the Pazyryk entry (very brief) says it's an Iron Age culture but then the Scythians entry explicitly mentions Pazyryk already in the Bronze Age.

      It's not always simple to define culturally a site or a burial anyhow. Is this, that or maybe something intermediate? Well, up to very erudite interpretation sometimes.

      "I'm thinking that perhaps three samples from that era are a weak basis for claiming, "that the Altai Mountains played the role of a geographical barrier between West and East Eurasian lineages until the beginning of the Iron Age"."

      Fair enough but still we first see a divide and then we see a mix. It's not just these three D samples but actually all the other exclusively "Western" mtDNA from the same period in the wider Central Asia area. So even if you can't say that the barrier was here or there... it's clear that there was some sort of barrier against "Eastern" mtDNA flow Westward in the Central Asian steppes in the Bronze Age (and before). Barrier that vanished with the arrival of the Iron Age.

      "I think it's more accurate to simply claim that massive, east-west, demic expansion is an Iron Age phenomenon".

      But then again we also see penetration of Western lineages in areas of Eastern lineages like these Westernmost Mongolian sites.

      So their interpretation is actually valid and very plausible. Although some more data may be needed to consolidate their model, I've read of weirder theories with much less support, to be honest.

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    2. I tend to agree with most of the points you raise.

      My greatest objection, I think, is imagining that the Altai Mountains were some sort of impermeable barrier. Field reports suggest otherwise. It also seems to me that, from relatively remote times, if a mountain range could be crossed, it would be.

      Put another way, to my mind it may be too simplistic to suggest that the barrier to genetic flow, from east to west, was geographic. There might have been other reasons. It could have been that peoples of the Andronovo horizon dominated the steppes west of the Altai until after the Bronze Age, for instance.

      When the great bronze-consuming civilizations declined and in some cases collapsed, beginning in the early second millennium BCE or so, the bronze industry no doubt collapsed with them. Sites like Sintashta probably lost their reason to exist and, combined with shifting weather patterns, may have reduced or weakened or displaced steppe populations generally. This might have left in its wake a power or population vacuum later filled by north-eastern populations expanding in the Iron Age.

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    3. Obviously not "impermeable" but a barrier of some relevance they do seem to be. Reading now on them I find references to few and difficult passes, etc. Actually the classic connections between West and East Eurasia go North and South of the Altai Mountains wedge and when we talk of the region of Altai (connected to West Eurasia since Aurignacian times) we usually mean the Siberian area NW of the mountains in the Upper Ob and sometimes also Yenisei basins.

      "... if a mountain range could be crossed, it would be".

      By how many people? How easily. Mountains are barriers except, to some extent, for peoples who have retreated towards them and use them as rearguard fortress and pastures (like Basques and some other mountain peoples through the World).

      So they do act as containment. We must understand that no barrier is absolute, at least on Earth, but that the added difficulty they pose is enough to deter or delay flow, keeping peoples at both sides clearly distinct (the few who do cross are absorbed and leave no or very limited legacy because of the laws of genetic drift, which act against minority elements normally).

      The last you say about "bronze consuming civilizations"... sounds totally unbelievable to me. If you needed bronze you produced it locally most of the time; raw metals may have been traded but bronze surely not in most cases (if anything, quality finished items which would be luxury items and therefore less important). I don't think either that bronze cultures collapsed in some sort of domino effect nor that a backwater culture like Pazyryk, which seems to be at both sides of the Bronze-Iron notional divide, could be much affected for what may happen in, say, Troy or Ugarit. They were just shepherds in a feudal-style society in the last corner of the World (there was no "Silk Road" yet of was just beginning to coalesce at most).

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    4. PS- Also at the Altai Mts. sits the geographical gaps that separate the West Eurasian steppe from the Mongolian-Manchurian one. It's a barrier of some sort, even if "absolute" is too big a word.

      This map can give an idea of the biome change precisely at the border between Russia and Kazakhstan on one side and China and Mongolia in the other: http://en.wikipedia.org/wiki/File:Vegetation-no-legend.PNG

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    5. "By how many people? How easily."

      Not many and, as I say in general, it seems to me that massive demic movements in eastern Eurasia are an Iron Age phenomenon -- Scythians, Mongol hordes, &c. Or at least there is little if any evidence of such mass movements in the Bronze Age in that part of the world.

      As for the bronze industry, this is my current understanding, however unbelievable it might seem. I'm sure that every Bronze Age culture wished that they could enjoy their own local production facilities but, alas, then as now, copper cannot be condensed out of the atmosphere and had to be mined and smelted from ore. This ore was not evenly distributed and I have no evidence that copper ore was traded or transported as you seem to suggest.

      Besides, and as I can only repeat, Sintashta tells us that at least one people of the Andronovo horizon were exploiting copper-ore deposits on an industrial scale. That scale makes little sense, unless these simple shepherds of the steppe had a market for all that metal. E E Kuz'mina suggests that these peoples crossed the Eurasian steppes in wagon trains, much as peoples in that part of the world were still doing well into the 1800s. She further suggests that this might be why their towns were round and often double-walled, since when camped they likely circled the wagons in the usual way on the Russian steppe: wheel-to-wheel and traces inward, with the women, children, and livestock sheltered inside. Obviously, with such technology a people were, at least in theory, capable of transporting large quantities of even high-value goods over vast distances.

      Your claim that there was no "Silk Road" in the Bronze Age is only true in the most narrow sense, in that, yes indeed, there was no silk traded westward until Han Wudi, at least so far as we know. But lapis lazuli was mined in Badakhshan as early as the fourth millennium BCE and its trade was so important and extensive in the later Bronze that the Harappans ascended the Khyber Pass and established the depot of Shortugai, on the upper reach of the Oxus, ca 2000 BCE.

      It's important to remember that the Silk Road was not really a road or even a route, at least in the way we speak of such things today. In reality it was a network of ancient trackways and no one, not even at its height, traveled the whole length of it, from the heartlands of the Yellow River to western Eurasia. Some segments of this network were facilitating long-distance trade sooner than others but the record indicates that some luxury goods were already flowing westward, from far north-eastern Afghanistan to as far as Egypt, as early as the latter's Old Kingdom.

      Segments of the Silk Routes through Central Asia could conceivably date to the local Neolithic, I think, and were theoretically capable of moving substantial quantities of goods from ca 2600 BCE onward, with the domestication of the Bactrian camel.

      "They were just shepherds in a feudal-style society in the last corner of the World..."

      Sure, the Pazyrik were, but the peoples that I suggest might have hampered their westward expansion were shepherds that happened to possess some of the more advanced transportation and metallurgical technologies in the world at that time.

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    6. Copper is a quite common material in fact. Tin would be the main restriction (I find really hard to believe that the only difference between arsenium-bronze and true bronze is toxicity, really).

      "... copper ore was traded or transported as you seem to suggest".

      Copper and tin ingots have been found in the exact apportions to make bronze in at least one and I believe that several sunken ships from the bronze and iron ages. There was a finding near Turkey years ago for example. I'm also positive that the tin used in Greek and other Eastern Mediterranean foundries in the 2nd millenium BCE was exported from the Atlantic even if we only have indirect evidence: it's just much easier to transport a ton of tin (which eventually allows for 10 tons of bronze) than the 10 tons of finished bronze ingots.

      I'd dare say that the most important resource for any metallurgy is wood (to make charcoal, mineral coal was seldom used in antiquity) and then the primary mineral (in this case copper). But copper was very common before the late 20th century's unprecedented extraction and semi-depletion. You seldom have all ingredients in any single place, so transporting them is normal. Instead buying swords from your potential foe may be very problematic.

      In fact trade of raw or semi-processed materials goes back to the Chalcolithic when, not just copper and other metals but specially quality flint was traded in relatively large networks to be later shaped as tool in destination or even hoarded as some sort of precious reserve occasionally.

      As for Sintashta, 2100 BCE is not any impressively early date. They belong to the Eruo-Mediterranean area, not East Asia, being correlated instead with the West Asian and peripheral Bronze Age, which is at least as old as 3300 BCE. Whatever they were theoretically "capable" of doing, I require more clear direct evidence that they actually did. Otherwise it's mere speculation.

      As for trade with Afghanistan, it is simply not comparable at all with the trade routes with East Asia which was what I meant by "Silk Road". Afghanistan and Central Asia almost wholly fall in the West Eurasian continental region, so not the same at all.

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    7. Maju, if you really believe so strongly that the facts are on your side, then please consider changing the Sintashta culture article at Wikipedia.

      Much of what you say rather supports my point. Finds of copper ingots are not evidence of trade in metallic ores or the even distribution of copper deposits across the ancient world. It actually supports what I said, that ore was mined and smelted at facilities near the extraction site. This is exactly what we find these Andronovo peoples doing at Sintashta and doing it on an industrial scale.

      You are probably correct, and the availability of fuel was indeed an important consideration. Again, that rather points us to the north, across the steppe, doesn't it?

      You are also correct that flint was traded from very early times, probably increasingly so from the Mesolithic through Neolithic, and the same is true of precious and semi-precious stones. This is why you shouldn't be so quick to dismiss proto-historic trade along the Great Khorasan Road.

      As for Sintashta, 2100 BCE is not any impressively early date. They belong to the Eruo-Mediterranean area, not East Asia, being correlated instead with the West Asian and peripheral Bronze Age, which is at least as old as 3300 BCE.

      Why choose 3300 BCE? Wikipedia says copper crucibles appear in the pre-Harappan era -- Mehrgarh II-III, at 3500 BCE or earlier, Kunal may be that early as well -- but even then, and despite evidence of long-distance trade and sophisticated industries, urban society remained some centuries in the future. There was as yet no substantial global demand for copper and bronze.

      The late third millennium was a very different world, though. Extensive, long-distance trade was central to great economies, like that of the Indus Valley, and urban civilizations throughout the ancient world created an insatiable market for copper and bronze. Demand was very high and sites like Sintashta appear to have been purpose-built to meet this demand.

      As for trade with Afghanistan, it is simply not comparable at all with the trade routes with East Asia which was what I meant by "Silk Road". Afghanistan and Central Asia almost wholly fall in the West Eurasian continental region, so not the same at all.

      Consequently, since I did not suggest that anyone moved substantial quantities of copper through the Tarim Basin in the third millennium BCE, the point is rather irrelevant.

      If Anthony and company are correct, and sites like Sintashta were supplying copper and bronze to trading economies like the BMAC, then it is precisely this west-Eurasian trade network that is under discussion.

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    8. I don't believe "so strongly" in anything but I do fail to see any strong evidence on your side.

      The Shintashta entry of Wikipedia (which I see no reason to change), says that this culture existed since c. 2100 BCE (not before) and that it existed in Europe (not Altai). It also mentions Central Asia but from context it's obvious that it only means the portions closest to Europe of Kazakhstan and West Siberia; see map, where Shintashta-Petrova is drawn in bright red (larger orange area is max. expansion of the derived culture of Andronovo, c. 1500 BCE).

      All you imagine around it is speculation on your side and the more you insists without providing clear evidence, the less I will believe in it (logically).

      "Why choose 3300 BCE?"

      Because it's the earliest date I found for Bronze Industry on Earth (West Asia) - but c. 3000 is maybe more realistic? Unsure because Troy I is already Bronze Age and is from that date - and it actually seems to be importing the tech towards Europe from further East.

      The archaeology of Troy is that of the Bronze Age for what we care anyhow: it arose with the beginnings of Bronze Age and collapsed (was destroyed by the Greeks as we know well) at the very end of it.

      "... copper crucibles appear in the pre-Harappan era -- Mehrgarh II-III, at 3500 BCE or earlier"...

      Copper is not bronze! Soft metals' simple metallurgy is known since "always", at least since Neolithic consolidation. There's a copper foundry in Serbia dated apparently to 7000 BCE! It means (almost) nothing because copper is not good compared to flint and because the temperatures and knowledge needed to do such a simple metallurgy is not much greater than for simple pottery or bread baking. It took a long time after that until people began forging bronze in West Asia.

      "If Anthony and company are correct, and sites like Sintashta were supplying copper and bronze to trading economies like the BMAC"...

      Isn't BMAC older than Shintashta? Isn't copper common in Central Asia (actually it's one of the big copper producers nowadays)? Isn't Bronze tech older in West and Central Asia (or even the Balkans) than in Eastern Europe?

      Who is Anthony, by the way?

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  2. "We must understand that no barrier is absolute, at least on Earth, but that the added difficulty they pose is enough to deter or delay flow, keeping peoples at both sides clearly distinct"

    The Altai region does not seem to have been much of a barrier during the Middle Paleolithic. And possibly not during the Early Upper Paleolithic. So the 'barrier' was crossed at opportune times before even the Bronze Age.

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