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Tuesday, May 24, 2016

Corded Ware women more mobile than their men


From a new paper at PLoS ONE on the diet and mobility of Corded Ware (CW) people in Central Europe (emphasis is mine):

Regarding the formation of the CW, some archaeologists point out the contribution of different regions to the material set of the "CW-network", while others note similarities with the steppe, in particular with the Yamnaya culture, as a possible area of origin. This is based on similarities in burial rituals. Some authors have suggested that this culture practiced a form of mobile pastoralism, which spread towards the west through migration and/or cultural influence, and gave rise to the CW. In the process, Indo-European language would also have spread over Europe [3, 4, 5, 6, 7]. Recently, these hypotheses have gained support from aDNA studies of Yamnaya and CW burials. Allentoft et al [8] and Haak et al. [9] show that a genetic transformation took place in areas where previous Neolithic DNA was heavily reduced and complemented by Yamnaya DNA. This new genetic presence was lasting and provided much of the genetic material for contemporary European populations. There is increasing evidence for some kind of population reduction or crisis toward the end of the middle Neolithic facilitating this introduction of new genes (e.g. [10]) and recent research has documented the presence of plague among Yamnaya and Corded Ware individuals [11], which may have spread among Neolithic populations prior to the migrations.

...

The number and proportion of females with distinctive strontium isotope ratios is notable and suggests that women were more mobile than males in CW society. Such evidence fits well with recent genetic information documenting more varied haplogroups among CW females [14]. Müller et al. [2] suggest female exogamy as a means of maintaining lineage identify in the face of rapid, long-distance mobility. Haak et al. [25] also reported genetic and Sr isotope ratio differences between males and females at Eulau, Germany, suggesting female exogamy. The fact that such a difference is identifiable at all also suggests that males were largely stationary, at least in the sense that they were mostly born, raised and buried in the same locality. We suggest that this reflects a stable exogamic system where women moved to their husband’s settlements, existing at Bergrheinfeld for several generations. As no distinctions in burial treatment were associated with incoming women, either the exogamic exchange involved only CW groups, or incoming women were completely integrated into CW society.


Citation...

Sjögren K-G, Price TD, Kristiansen K (2016) Diet and Mobility in the Corded Ware of Central Europe. PLoS ONE 11(5): e0155083. doi:10.1371/journal.pone.0155083

Monday, May 23, 2016

The Rakhigarhi 15


Samples from fifteen Indus Valley Civilization (IVC) skeletons recently unearthed at Rakhigarhi have been sent to three different ancient DNA labs for analysis. The Tribune India reports that one of these labs is located at Howard University, USA (see here).

Why Howard University and not, say, Harvard University? Or did the reporter really mean the Howard Hughes Medical Institute?

It might be an important detail, because Harvard's David Reich is affiliated with the Howard Hughes Medical Institute. So if that's actually where the IVC samples are going, we're likely to see good quality genome-wide genotype data from them at some point, probably in the not too distant future.

In any case, I know that a lot of people are eagerly awaiting ancient DNA from the IVC, so a paper based on just basic uniparental markers from up to fifteen IVC individuals is really going to cause a stir. For instance, check out this discussion thread at a popular Indian forum: Out-of-India - From Theory to Truth: Part 2.

Holy shit. Let's be realistic here; the probability that ancient DNA from South Asia will make the Out-of-India theory (OIT) a credible proposition is nil. I'd say we have a better chance of finding extraterrestrial life in the next few years than the OIT ever becoming a viable option in the Proto-Indo-European (PIE) homeland debate.

If we eventually see genotype data from IVC samples, my guess is that they'll either resemble present-day Dravidians from South India, Brahuis from Pakistan with no discernible recent admixture from Africa and Arabia, Munda-speaking tribals from near the Himalayas, or a complex mixture of two or all three of these groups.

Unfortunately, knowing this won't tell us what language the IVC people spoke. The only way to learn that is to decipher the Harappan seals.

However, comparing the IVC samples to present day North Indians, particularly high caste North Indians like Brahmins, is likely to reveal whether South Asia experienced a large scale population shift during or shortly after the IVC collapse, especially at the top end of its society. If so, it's also likely to tell us what type of population(s) moved into South Asia at this time and basically laid the foundations for modern South Asia. This information is going to be very valuable in the PIE homeland debate.

So, now the waiting game begins.

Update 24/05/2016: I ran a series of D-stats of the form D(IVC_proxy,Test_population)(Source_population1,Source_population2) to try and profile the non-IVC ancestors of present-day high caste North Indians. All results with Z scores of > negative 2 are in bold print.

If we assume that the IVC people were a lot like present-day Dravidian-speaking South Indians, which I think is a pretty good assumption, then the newcomers came from the Bronze Age Eurasian steppe, and were probably very similar to the Poltavka outlier individual that I blogged about recently. See here.


If, on the other hand, the IVC people were basically like the least admixed Brahuis from present-day Pakistan, then the newcomers were very similar to the Afanasievo pastoralists of the Early Bronze Age (EBA) Altai region.


But, if the IVC people were like the present-day Munda-speakers from near the Himalayas, then the newcomers were probably a mixture of both Kotias-related agriculturalists from West Asia and pastoralists from the Eurasian steppe. Note the lack of any Z scores lower than -2. In other words, the results are very close to neutral.


See also...

Rakhigarhi ancient DNA paper probably a while away

Sunday, May 22, 2016

Parallel migrations in brown bears and humans within Eurasia


If, as per the abstract below, a major part of the Native American gene pool derives from the Altai-Sayan refugium, then it's likely to be the Ancient North Eurasian (ANE) part, rather than the East Asian part. So I'd say that for now the Altai-Sayan region looks like a pretty good option for the homeland of the ANE people (aka Mal'ta cluster).

Climatic changes during the Late Pleistocene had major impacts on the populations of many plant and animal species. During this period, humans and large mammals, e.g. brown bear and moose, were subject to analogous phylogeographic pressures and were linked by important ecological processes. However, evidence of human dispersal in northern Eurasia during the Late Pleistocene is scarce. Analysis of large mammals therefore has the potential to shed light on the population processes of humans during this period. We address several unresolved issues regarding the Late Pleistocene demography of brown bears: (a) the putative locations of refugia; (b) the direction of migrations across Eurasia and into North America; and (c) parallels with other mammals, including humans. We present results based on more than 200 complete mitochondrial genome sequences from Eurasian and North-American brown bears. Bayesian phylogenetic analysis revealed that most individuals belong to a very large Holarctic clade. The MRCA of this clade lived ca 40 thousand years ago, most likely in the Altai-Sayan area, a known Late Pleistocene refugium in Asia. We propose several migration scenarios for bears and suggest that brown bears and humans underwent a series of parallel migrations in Eurasia and to North America during the Late Pleistocene. Moreover, both species exhibited a demographic standstill in Beringia before colonizing North America. Synchrony in the timing of past migrations and standstill implies that the ecology of large mammals includes key limiting factors that can enhance our understanding of ancient human movements and on large carnivore conservation.

Saarma et al., Parallel migrations in brown bears and humans within Eurasia and into North America during the Late Pleistocene, ConGenomics 2016 abstract.

Wednesday, May 18, 2016

Yamnaya = Khvalynsk + extra CHG + maybe something else


Thanks to recently published ancient DNA it's now generally accepted that the Yamnaya pastoralists of the Pontic-Caspian Steppe were basically a mixture of Eastern European Hunter-Gatherers (EHG) and Caucasus Hunter-Gatherers (CHG).

However, I thought it might be useful to dig a little deeper with the D-stats/nMonte method to see what else crops up. I put together a special datasheet for the job, with Yamnaya Samara featured both in the rows and columns. It's available for download here. The nMonte R script can be gotten here.

Using the most plausible reference samples currently available - almost all of them older than Yamnaya, and thus unlikely to skew the results with Yamnaya admixture - reveals the following models for the two Yamnaya sets from Kalmykia and Samara, respectively.

Yamnaya_Kalmykia
Khvalynsk 57.7
Kotias 28.3
Hungary_EN 12.9
Ulchi 1.1
AfontovaGora3 0
Anatolia_Neolithic 0
Karelia_HG 0
Loschbour 0
MA1 0
Motala_HG 0

distance%=1.9125 / distance=0.019125

Yamnaya_Samara
Khvalynsk 56.75
Kotias 26.4
Hungary_EN 10.85
Karelia_HG 4.4
Loschbour 1.6
AfontovaGora3 0
Anatolia_Neolithic 0
MA1 0
Motala_HG 0
Ulchi 0

distance%=2.1354 / distance=0.021354

Very interesting but hardly surprising. Essentially what we're seeing there is potentially very strong genetic continuity from the Eneolithic to the Early Bronze Age on the Pontic-Caspian Steppe. In other words, from Khvalynsk to Yamnaya.

However, at some point between the Eneolithic and the Early Bronze Age, the steppes saw a major influx of extra CHG, represented by the ~27% of Kotias-related admixture. Considering the relevant uniparental data, with lots of Y-HG R1b and no Y-HG J among Yamnaya males, I'd say this CHG came with women.

Also, the relatively high admixture related to early Hungarian Plain farmers (Hungary EN) is a fairly curious detail that has not been reported before. If real, it probably represents gene flow from the Neolithic and/or Chalcolithic Balkans to the Pontic-Caspian Steppe. Again, in all likelihood it mostly came with women, perhaps from Tripolye-Cucuteni and/or Varna communities.

But, to make sure the results weren't erroneous - perhaps skewed by the worryingly high affinity between the two CHG genomes, Kotias and Satsurblia, both pseudo-diploid sequences - I reran the tests using a different version of the same datasheet (available here). In this version, Kotias and Satsurblia are part of a single Caucasus HG sample included in the rows.

Yamnaya_Kalmykia
Khvalynsk 53.95
Caucasus_HG 38.45
Hungary_EN 4.7
Motala_HG 2.9
AfontovaGora3 0
Anatolia_Neolithic 0
Karelia_HG 0
Loschbour 0
MA1 0
Ulchi 0

distance%=1.7492 / distance=0.017492

Yamnaya_Samara
Khvalynsk 56.7
Caucasus_HG 33.55
Hungary_EN 4.25
Loschbour 2.95
Motala_HG 2.55
AfontovaGora3 0
Anatolia_Neolithic 0
Karelia_HG 0
MA1 0
Ulchi 0

distance%=2.0964 / distance=0.020964

Yup, the Hungary EN contributions take a dive. But they're still above noise level (>2%), so they might well represent a real signal that entered the Yamnaya horizon or late Khvalynsk from the west. Can't wait to see how Yamnaya genomes from north of the Black Sea come out.

See also...

The Khvalynsk men

Saturday, May 14, 2016

D-stats/nMonte open thread #2


I put together a couple of D-stats datasheets featuring the Ice Age European samples from Qiaomei Fu et al. 2016. They're available for download here and here, and can be used as input for nMonte and 4Mix. For instance, a couple of models using nMonte:

Villabruna
ElMiron 99.8
Anatolia_Neolithic 0.2
AfontovaGora3 0
Esan_Nigeria 0
GoyetQ116-1 0
Kostenki14 0
Kotias 0
MA1 0
Neandertal_Altai 0
Ulchi 0
Vestonice16 0

distance%=5.9112 / distance=0.059112

Kotias
Anatolia_Neolithic 56.45
Kostenki14 24.1
AfontovaGora3 18.1
Esan_Nigeria 1.35
ElMiron 0
GoyetQ116-1 0
MA1 0
Neandertal_Altai 0
Ulchi 0
Vestonice16 0
Villabruna 0

distance%=8.3858 / distance=0.083858

Update 17/05/2016: I wanted to see what would happen if I changed the formula from D(Chimp,Rows)(Mbuti,Columns) to D(Chimp,Columns)(Mbuti,Rows). The new datasheets are available here and here. The results are very similar, although never identical, and I'm not sure at the moment which set of sheets works better.

Villabruna
ElMiron 99.5
Anatolia_Neolithic 0.5
AfontovaGora3 0
Esan_Nigeria 0
GoyetQ116-1 0
Kostenki14 0
Kotias 0
MA1 0
Neandertal_Altai 0
Ulchi 0
Vestonice16 0

distance%=5.8334 / distance=0.058334

Kotias
Anatolia_Neolithic 69.5
AfontovaGora3 24.3
Ulchi 5.35
Kostenki14 0.85
ElMiron 0
Esan_Nigeria 0
GoyetQ116-1 0
MA1 0
Neandertal_Altai 0
Vestonice16 0
Villabruna 0

distance%=8.6196 / distance=0.086196

See also...

Yamnaya = Khvalynsk + extra CHG + maybe something else

D-stats/nMonte open thread

D-stats/4mix tour of ancient Eurasia

Thursday, May 12, 2016

Following the mammoth herds?


The recent Qiaomei Fu et al. paper on the population genomics of Ice Age Europe was a fascinating read, but its sampling strategy left a big blind spot: Eastern Europe 24-34 kyr BP. Check out what happens to the maternal lineages of Eastern European mammoths at this time.


Basically, they're replaced by lineages native to North America. During the 14-24 kyr BP period, the rest of the European mammoth population is also affected.

Of course, this is also precisely the period when the so called Villabruna hunter-gatherer cluster appears in Central Europe, probably as a result of mixture between the remnants of post-Ice Age Europeans and a population relatively closely related to Caucasus and Siberian hunter-gatherers (see post and discussion here). Perhaps mammoth hunters?

No wonder then, that this is also the time when we see the first appearance of Y-chromosome haplogroup R1 in Europe; more precisely R1b1, in the ~14 kyr cal BP genome from Villabruna, northeast Italy, that defines the Villabruna cluster. After all, R is the sister clade of Q, the dominant Y-chromosome haplogroup in many parts of North Asia and the Americas.

Image credit...

Palkopoulou et al., Holarctic genetic structure and range dynamics in the woolly mammoth, Proc. R. Soc. B 2013 280 20131910; DOI: 10.1098/rspb.2013.1910. Published 11 September 2013

Friday, May 6, 2016

Villabruna cluster =/= Near Eastern migrants


I've been running a lot of Treemix analyses with the samples from the recent Qiaomei Fu et al. paper. And the impression I'm getting is that the authors missed the elephant in the room, the one with R1b painted on its big butt.

Now, it's true that Treemix output can't be used as unambiguous evidence in support of complex models. That's because in the absence of key samples the algorithm can get exceedingly creative in modeling the available data, sometimes to such extremes that the results might seem absurd.

However, when something keeps showing up again and again, even when using somewhat different samples and marker sets, and makes sense in the context of haploid and archaeological data, then at the very least it deserves serious consideration.

Here's a nice Treemix series that more or less captures the meat and potatoes of my many Treemix experiments with the Qiaomei Fu et al. dataset. For the archaeological contexts and other details about these ancient samples see here.








Below is my interpretation of the results:

- Villabruna is a sister clade of the earlier European Vestonice clade, but with significant input from an AfontovaGora3-related North Eurasian population, perhaps one that was living north of the Black Sea after the Kostenki people went the way of the dodo

- Hence, the R1b lineage carried by Villabruna I9030, the individual in this Treemix series, probably comes from the Eurasian steppe

- Kotias, a Caucasus Hunter-Gatherer, is in large part derived from the same North Eurasian population, hence the close relationship between Villabruna and Caucasus Hunter-Gatherers

- Villabruna and/or closely related foragers contributed significant ancestry to Neolithic Anatolians, and thus, indirectly, possibly to all extant Near Eastern and even many African populations

- Kotias is also closely related to Neolithic Anatolians, but probably mostly via a more basal population, perhaps the so called Basal Eurasians, native to the Near East prior to the Villabruna and/or related gene flow across the Near East and parts of Africa

- Present-day East Asians might be ancient hybrids with admixture from the same or very similar North Eurasian population, although as per the above mentioned quirks of Treemix, it's possible that the North Eurasians that contributed ancestry to Villabruna, Caucasus foragers and Eurasian steppe populations were in fact partly East Asian

So basically what I'm seeing are back migrations from Europe and the Eurasian steppe or Siberia to the Near East soon after the Ice Age. Yes, from Europe, although I admit that things can get fuzzy here.

That's because at the time much of the Aegean Sea was dry land, and thus there was no geographic barrier between the European Balkans and Asian Anatolia. The two regions, which might seem very distinct to us today, were basically one. So when I say Europe, I actually mean the ancient landmass now divided between the Balkans and Anatolia.

Or not? Are there any D-stats that we can run to either confirm or debunk my Treemix-based hypothesis? Feel free to post your proposals in the comments and I'll try and run them as soon as possible.

Update 07/05/2016: The plot thickens somewhat. I added MA1 to the line up, and now Villabruna shows minor Kotias-related ancestry. In other words, probably something from the Caucasus. The full series is available in a zip file here.


However, although interesting, this result doesn't change much. In fact, it adds more weight to the argument that Villabruna inherited his Y-chromosome from steppe foragers. That's because if this migration edge was a reflection of gene flow from Anatolia to Europe, I'd expect it to run from the Anatolia Neolithic branch, rather than the Kotias branch.

See also...

Following the mammoth herds?