August 21, 2016

Neolithic DNA from Southern Anatolia

I know, I know: I'm decaying into a total procrastinator. I don't have any excuse other than I don't feel like blogging as of late: neither on anthropology nor on politics. I rather feel like learning new stuff and playing, rather than writing and I lack of the structured environment to force myself to do otherwise than what I feel like most of the time. Being of compulsive temperament only worsens things.

I also know that this is not the proper way to start an article. Yes, I know. Do I even care?

So getting to mention now some of the stuff that I have not discussed in these last months and is definitely worth posting about. First of all this key study on more easterly Anatolian early farmers than those seen so far.

Intriguingly they are notoriously similar to those sequenced farther West (see here), what seems to support the model of Anatolian origin of European Neolithic peoples, largely ancestral to modern Europeans. However even Western Anatolian early farmers show already some extra admixture with the Paleoeuropean "WHG" component relative to their Southern Anatolian precursors. So, as the authors suggest, admixture between immigrant farmers and native foragers was a gradual and continuous process beginning in Asia Minor itself.

Gülşah Merve Kılınç, Ayça Omrak, Füsun Özer et al., The Demographic Development of the First Farmers in Anatolia. Current Biology 2016. Open accessLINK [doi:10.1016/j.cub.2016.07.057]

Summary

The archaeological documentation of the development of sedentary farming societies in Anatolia is not yet mirrored by a genetic understanding of the human populations involved, in contrast to the spread of farming in Europe [ 1–3 ]. Sedentary farming communities emerged in parts of the Fertile Crescent during the tenth millennium and early ninth millennium calibrated (cal) BC and had appeared in central Anatolia by 8300 cal BC [ 4 ]. Farming spread into west Anatolia by the early seventh millennium cal BC and quasi-synchronously into Europe, although the timing and process of this movement remain unclear. Using genome sequence data that we generated from nine central Anatolian Neolithic individuals, we studied the transition period from early Aceramic (Pre-Pottery) to the later Pottery Neolithic, when farming expanded west of the Fertile Crescent. We find that genetic diversity in the earliest farmers was conspicuously low, on a par with European foraging groups. With the advent of the Pottery Neolithic, genetic variation within societies reached levels later found in early European farmers. Our results confirm that the earliest Neolithic central Anatolians belonged to the same gene pool as the first Neolithic migrants spreading into Europe. Further, genetic affinities between later Anatolian farmers and fourth to third millennium BC Chalcolithic south Europeans suggest an additional wave of Anatolian migrants, after the initial Neolithic spread but before the Yamnaya-related migrations. We propose that the earliest farming societies demographically resembled foragers and that only after regional gene flow and rising heterogeneity did the farming population expansions into Europe occur.


Autosomal DNA


Maybe the most informative graph is this one (fig. 2):

Genetic Structure and Diversity of Central Anatolian Neolithic Populations
(A) PCA on contemporary west Eurasian populations onto which a total of 85 ancient individuals are projected from this study and previous studies. See Table S1 for number of SNPs per individual. Neighboring modern populations and ancient Anatolian populations are shown encircled. Modern population names are in italics.
Etc. (not so interested here in B, C and D, legend too long, check in the original paper)
Click to expand

It is interesting that, in spite of the Anatolian origin of this ancient ancestral population, they do not tend so much to modern Anatolian Turks but rather to Levant populations like Cypriots (closest ones), Lebanese, Palestinians, etc.

This is probably because, even if early Neolithic peoples of the Levant were not quite like them (see here again) they had become almost like them before the Bronze Age because of regional admixture, which I understand was mostly (but not only) north-to-south flow.

Notice that the Boncuklu (Bon) people had very low genetic diversity and they seem to be a dead end rather than directly ancestral. Instead, the Tepecik-Çiftilik (Tep) population seems a good proxy for the ancestors of Neolithic peoples of Western Anatolia and Europe. 

When we think about South Anatolia Neolithic, we usually think first and foremost about the famous Çatalhöyük site. Well, this ancient settlement is in the area of Boncuklu (to the West, both are near Konya) rather than that of Tepecik-Çiftilik (to the East, near Niğde), so it is quite possible that it is another demographic dead end, related but not directly ancestral to mainline European Neolithic. 

Personally I still think they could well have migrated at least partly by boat, along the southern Turkish coast but, until new data comes, I may need to alter my hypothesis of the ultimate origin being in the Northern Levant (Syria, Lebanon, Cyprus even) rather than Anatolia. These people of Tepecik-Çiftilik were, if not direct ancestors at least very closely related to the actual source population, which may well have lived closer to the coast in any case.



Mitochondrial DNA


The newly sequenced South Anatolian farmers had some of the lineages that were later present in Hungary's and Germany's "Danubian Neolithic", notably the now rare N1a1a1, found in 4/9 samples in this study. Also present were K1a (3/9, incl. one K1a12a), U3 (1/9) and N1a1b (1/9).

So it is time to dismiss the hypothesis that claimed N1a1a1 as a European aboriginal lineage: it came with the immigrant farmers and now there can be no doubt about it.

4 comments:

  1. This comment has been removed by the author.

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  2. Thanks. Judging from that PCA, the Tepecik samples from South Central Turkey, do appear to be more leaning toward the Caucauses and Iran, which is still in line with the idea that there was reciprocal gene flow between Anatolian and Iranian Neolithics. And there is still plenty of ancient DNA geographically East, which which has not yet been sampled. Also note the intermediate position of Bronze Age/Iron age samples, with respect to WHG and Caucaus/Iran (EHG/Iran_Neolithic), most of which are in close proximity to the position of modern-day North and Western Europeans. This is suggestive of the possibility that Bronze Age populations emerged as the dominant type in Europe.

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  3. There should be a general genetic flow between the various Neolithic groups (and also, even if less important, bordering "barbarians" such as WHG to the west or EHG to the North at some point). However notice please that the Anatolian Neolithic is more recent than the ones of the Fertile Crescent proper, both Levant and Zagros regions. I must mention here that the Mesopotamian flatlands have generally not yielded finds until also later, with an archaeological trail Zagros Neolithic → Middle Mesopotamia (Samarra) → Lower Mesopotamia (Sumeria). Furthermore, there is even evidence of the Levant Neolithic (PPN A/B) being the center of agriculture (cereals at the very least, unsure about legumes), while Zagros Neolithic was the center of pastoralism (sheep and goat at the very least, cows are domesticated only later in the South Anatolian context, not sure about pigs).

    The two traditions interact in the western Zagros fold (Western Kurdistan, etc.) particularly (around Göbekli Tepe even if the monument is still pre-Neolithic, quite a striking fact in itself) and it's probably over there where the seeds of a distinctive (South) Anatolian Neolithic coalesced. This South Anatolian Neolithic is older than the Aegean or Iranian ones but is still more recent than the Fertile Crescent ones, and surely derived from those.

    "Also note the intermediate position of Bronze Age/Iron age samples, with respect to WHG and Caucaus/Iran (EHG/Iran_Neolithic)"...

    Not sure what you mean. You're probably referring to the Lazaridis 2016 paper, which does have Bronze Age samples from Armenia and Palestine, which seem to have a slightly greater amount of WHG (not really of EHG, only very tiny in the Levant case, a bit less in the Armenia case) than their respective predecessors. I wouldn't make a lot of that, if anything it seems to imply more interaction with populations carrying WHG, such as those from Anatolia, the Aegean or maybe even North Africa (which is the neglected "ugly little duck" of West Eurasian genetics but clearly has a good chunk of Iberian-derived genetics which must be Paleolithic in origin).

    Notice anyhow that in the late Bronze Age Levant (or Retenu/Canaan as it was called back in the day) there were already people of European origins, such as the Shardana (surely Sardinians) or the better known Philistines (surely some sort of Greeks or Pelasgians). It's possible even that some migrations W→E happened earlier, maybe in form of refugees from the Indoeuropean invasions or interactions with SW Europe: some artifacts strongly suggest contacts between Iberia and Syria/Cyprus even in the Chalcolithic for the West, what would be early BA in the East. Also we have to consider where did all the pre-Indoeuropean first bronze metallurgists from the Balcans (the first bronze known on Earth) go c. 3000 BCE, maybe to the Southeast? These issues are very much open in terms archaeological but I would say that one thing is clear: the Chalcolithic/Early Bronze Mediterranean, even if less dynamic than in later times, was not a mere barrier but also a space for interaction between the various populations along its shores. This became much more dynamic in the late Bronze Age (early/middle Bronze Age in the West).

    "This is suggestive of the possibility that Bronze Age populations emerged as the dominant type in Europe."

    I'm utterly lost at this sentence. Are you talking of Europe or West Asia? And, if Europe, what exactly do you mean? Because quite obviously the Levant-BA population is not quite like Europeans at all, modern or ancient, even if it is pretty much like modern Palestinians.

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  4. Oops, I realize now that you are talking about the European (mostly Steppe) Bronze Age samples in the PCA above. Sorry for the rant.

    I see two issues in jumping to conclusions: (1) they are almost only Steppe samples, so other studies are better for that, because they do include samples from Central Europe (not enough but something) and (2) the all West Eurasia PCA is not ideal to properly represent Europe: it'd be best to use a Europe-only or Europe-mostly PCA, which mostly rotates down to the horizontal plane what here appears as diagonal pattern, separating more clearly Basques from Sardinians, etc., while retaining the Sardinia-Steppe axis perfectly vertical, now as PC1 -- the PC2 would be a Basque-East Mediterranean opposition for which both Sardinians and Steppe/NE peoples are neutral. That would be a much more clear representation of European genetics, both modern and ancient, unless we are specifically dealing with the origin of Neolithic peoples or stuff like that.

    But I would agree that the Indoeuropean invasions from the Northeast were a game-changer that dramatically altered European genetics west of the Dvina and Dniepr basins (there seems also to have been a backflow to Eastern Europe). However important populations such as Basques, Iberians and Sardinians seem nearly unaffected by this Indoeuropean genetic flow, while others like French, Italians, etc. seem only somewhat affected. Even in the most dramatic cases like Central and North Europe, the admixture with late Neolithic peoples seems around 50-50.

    I still await more and more clear archaeogenetic data from the West, where we have way too few data-points, something also affecting the Southeast to a large extent.

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