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Friday, January 30, 2015

Half of our ancestry comes from the Pontic-Caspian steppe

Here's the latest teaser for the new David Reich et al. paper on the ethnogenesis of present-day Europeans. It's part of an abstract for a seminar to be held by Professor Reich at Jesus College, Oxford, on February 9. Interestingly, it argues that migrations from the steppe resulted in a ~50% population turnover across northern Europe from the late Neolithic onwards, which is very much in agreement with recent discussions on the topic at Eurogenes (for instance, see here).

By ~6,000-5,000 years ago, a resurgence of hunter-gatherer ancestry had occurred throughout much of Europe, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but also from a population of Near Eastern ancestry. Western and Eastern Europe came into contact ~4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced ~3/4 of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least ~3,000 years ago, and comprises about half the ancestry of today’s northern Europeans. These results support the theory of a steppe origin of at least some of the Indo-European languages of Europe, and show the power of genome-wide ancient DNA studies to document human migrations.

Source: Ancient DNA documents three ancestral populations for present-­day Europeans

Update 11/02/2015: Massive migration from the steppe is a source for Indo-European languages in Europe (Haak et al. 2015 preprint).

Haak et al., Massive migration from the steppe is a source for Indo-European languages in Europe, bioRxiv, Posted February 10, 2015, doi:

Friday, January 23, 2015

Yamnaya genomes are a 50/50 mix of eastern Euro foragers and something else ANE-rich

I'm posting a new entry about the upcoming Corded Ware/Yamnaya paper because the last entry (see here) now has over 400 comments which aren't easy to load for many people.

One of the authors of this eagerly awaited paper, Nick Patterson of the Broad Institute, briefly joined our discussion. Nick's contribution is much appreciated. He wasn't able to reveal a great deal, because the manuscript is in submission, but he did make a couple of interesting points:

- the paper will feature Y-haplogroup results from the Yamnaya culture, represented by nine samples in all, including seven males

- the population with Near Eastern ancestry that mixed with the Eastern Hunter-Gatherers (EHG) on the Russian steppe to form the Yamnaya pastoralists by 5,000 YBP was also "rich" in ANE

- ancient DNA from the Caucasus, Iran and India is probably necessary to work out how the Indo-Europeans got to India, but the paper won't feature such data

It's nice to hear that Y-haplogroups aren't being ignored. My opinion is that they're at least as important as genome-wide data when tracking the movements across vast space and time of highly patriarchal and patrilineal groups like the ancient Indo-Europeans.

Indeed, we already know that the Slavic, Baltic and Norse-specific R1a1a1b1, defined by the Z282 mutation, is the sister clade of the Indo-Iranian-specific R1a1a1b2, defined by Z93. Thus, if the Yamnaya males were found to belong to these or upstream markers, this would suggest that they were the paternal ancestors of many Balts, Scandinavians, Slavs and Indo-Iranians, and correlate very nicely with the linguistic and archeological "steppe hypothesis" of Indo-European origins.

In fact, even if analyses based on high density genome-wide data suggest that Indians don't harbor any genome-wide European ancestry, we'd still have to accept the likelihood of gene flow - albeit perhaps very indirect gene flow - from the European steppe to India because many Indians belong to R1a1a1b2.

The second point made by Nick is perhaps surprising, but at least for me not totally unexpected. That's because we've already known for a while that the Yamnaya genomes can be successfully modeled as half Karelian EHG and half present-day Armenian (see here), and according to my own estimates Armenians carry an average of 15.5% ANE.

The fact that these Armenian-like, ANE-rich newcomers dampened the genome-wide affinity to ANE-proxy MA-1 on the Russian steppe might look like a contradiction, but not if we remember that the higher the Near Eastern ancestry the lower the genome-wide affinity to MA-1, and also consider that the steppe foragers probably carried a lot more ANE than the newcomers.

Actually, as far as I know, all of the Yamnaya samples in this study come from the Samara Valley, which is some distance north of the Caspian Sea near the southern Urals. So it makes senses that the pseudo Armenians who turned up there more than 5,000 years ago were not like the Neolithic farmers of Western and Central Europe, who lacked ANE.

I'd say that this as yet unidentified group (wild guess: immediate ancestors of the Repin culture people?) was the result of an admixture event, or perhaps a series of admixture events, with ANE-rich foragers somewhere on the steppe south of the Samara. If so, I won't be surprised if it turns out that R1a only appeared in the Samara Valley after their arrival.

In any case, it looks like even after this paper comes out, we'll still need a lot more ancient DNA from across Eurasia to help map out the early Indo-European dispersals with any confidence.

Update 11/02/2015: Massive migration from the steppe is a source for Indo-European languages in Europe (Haak et al. 2015 preprint) .

Monday, January 19, 2015

Ancient DNA points to the Eurasian steppe as a proximate source for Indo-European migrations into Europe

This is yet another teaser for the upcoming Corded Ware/Yamnaya paper from the Reich lab. Sadly, it doesn't mention Y-chromosome haplogroups, so perhaps the authors are going to tackle this issue later. However, check out what they say about the German and Spanish farmers being of the same stock, and the resurgence of hunter-gatherer ancestry in Western Europe after the early Neolithic. Fascinating stuff.

Ancient DNA points to the Eurasian steppe as a proximate source for Indo-European migrations into Europe

David Reich and Nick Patterson

Abstract: We generated genome-wide data from 65 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of about 390,000 single nucleotide polymorphisms. This strategy decreases the sequencing required to obtain genome-wide data from ancient DNA samples by around 1000-fold, allowing us to study an order of magnitude more individuals than previous studies and to obtain new insights about the past. We show that in western Europe, the farmers of both Germany and Spain >7,000 years ago were descended from a common ancestral stock. These farmers did not replace the earlier hunter-gatherers, but continued to mix with them, leading to a resurgence of hunter-gatherer ancestry in both Germany and Spain ~1,000-2,000 years later. In eastern Europe, the hunter-gatherers of Russia >7,000 years ago were distinct from those of the west, having an increased affinity to a ~24,000 year old individual from Siberia, but this affinity was reduced by ~5,000 years ago in the Yamnaya steppe pastoralists because of admixture with a population of Near Eastern ancestry. Western and Eastern Europe collided ~4,500 years ago with the appearance of the Corded Ware people in Central Europe, who derived at least two thirds of their ancestry from an eastern population closely related to the Yamnaya. The evidence for mass migration into Europe thousands of years after the arrival of agriculture, in combination with linguistic and archaeological data, makes a compelling case for the steppe as a proximate source for the spread of Indo-European languages into Europe.

Source: INA Kolloquium Ws 2014/15

Update 11/02/2015: Massive migration from the steppe is a source for Indo-European languages in Europe (Haak et al. 2015 preprint) .