Thursday, May 4, 2017

Conference Abstract Re Big Bell Beaker Paper Released

The first hints about the Bell Beaker Behemoth paper are out, in the form of a conference presentation abstract predating the release of the paper itself (which may be out by the time that the conference presentation is delivered). It answers some questions (mostly in ways we would expect) while leaving the answers to lots of other key questions under answered. Via Eurogenes (emphasis and paragraph breaks mine). Razib's first take on the abstract is here.
The Bell Beaker Complex (BBC) was the first widely distributed archaeological phenomenon of western Europe, arising after 2800 BCE probably in Iberia and spreading to the north and east before disappearing at the latest by 1800 BCE. An open question is the extent to which the cultural elements associated with the BBC spread through movement of ideas or people. 
We present new genome-wide DNA data from 196 Neolithic and Bronze Age Europeans – the largest report of genome-wide data in a single study to date – and merge it with published data to form a dataset with 109 BBC individuals that provides a genomic characterization of the BBC across its geographic and temporal range. 
In contrast to people of the Corded Ware Complex who were partly contemporaries of the BBC in central and eastern Europe and who brought steppe ancestry into central Europe through mass migration and replacement of local populations, we show that the initial spread of the BBC into central Europe from the Iberian Peninsula was not mediated by a large-scale migration but rather through communication of ideas. 
However, the further spread of the BBC beyond central Europe did involve mass movement of people. Focusing on Britain, which includes 81 of our new samples in a time transect from 3900-1300 BCE, we show that the arrival of the BBC around 2400 BCE was mediated by migration from the continent: British individuals associated with Beakers are genetically indistinguishable from continental individuals associated with the same material culture and genetically nearly completely discontinuous with the previously resident population. Such discontinuity persists through to samples from the Bronze Age, documenting a demographic turnover at the onset of the Bronze Age that was crucial to understand the formation of the present-day British gene pool. The arrival of the BBC in Britain can thus be viewed as the western continuation of the massive movement of people that brought the Corded Ware Complex and steppe ancestry into central Europe a few hundred years before.
Olalde, Reich, et al., "Western Europe during the third millennium BCE: A genetic characterization of the Bell Beaker Complex," AetG17 abstracts


* Coming Soon. A comment at the Bell Beaker blogger blog provides some insight on when the paper itself will become available. Craig Faber says (emphasis added):
IƱigo Olalde and David Reich are doing a presentation at a workshop at Kiel University that runs from May 17 to 22. Their presentation will focus on population turn-over in Britain associated with the arrival of the Bell Beaker phenomenon there, using new data from Britain, and new and previously published aDNA from other countries for comparison.

The main news here, I think, is that results from the Behemoth study are currently embargoed till publication, and, by the time of the workshop, they no longer will be. The abstract for Reich and Olalde's upcoming presentation in Kiel provides no insight into what was going on in Iberia and Ireland in the same time period, but the Behemoth paper itself probably will (and hopefully they'll have some data from France as well). That's my take on this anyway.
* Dates. The beginning dates in Iberia and Britain sound about right. I would have put the end of the Bell Beaker period in Western Europe at 1300 BCE to 1200 BCE. The distinction matters quite a bit for linguistics purposes and in analyzing the cause of the Bell Beaker decline. Of course, part of the issue is which archaeological cultures to treat as Bell Beaker derived.

* Linguistic Speculation. The Abstract Is Silent On Language. The authors have interestingly backed away from the linguistic claims that were a source of great dispute within their group in their last paper. This is appropriate. The evidence regarding Bell Beaker historical linguistics is much less clear. But, certainly, one would not expect a population engaged in mass folk migration to experience language shift. 

Has There Been A Struggle Over Data Interpretation? One of my theories on why the Bell Beaker Behemoth paper has taken so long to get into print after the data was available but embargoed is that there has been infighting, again, over how strong a statement to make about the linguistic implications of the genetic data. My take would be that this abstract suggests that the "avoid making linguistic claims" camp has largely won the battle. Perhaps those who wish to make linguistic claims will publish separate satellite papers (maybe even advancing competing theories). 

The Indo-European Scenario. If the Bell Beaker people spoke an Indo-European language, you'd expect it to be an early version of Celtic. But, the Celtic language family seems far too young, unless you have a phenomena like the Romance languages where the Bell Beaker languages were homogenized at the peak of the Bell Beaker era though long distance migration and only started to form regional dialects (a la the post-Latin Romance languages) when the Bell Beaker phenomena collapsed. In this scenario, the Basque people and related languages that went extinct just at the dawn of attested history nearby, where a case of Indo-Europeans of a Celtic persuasion experiencing language shift and religion shift to a pre-existing first farmer language and faith, perhaps due to high levels of intermarriage with local Iberian women in a male dominated migration. 

The Non-Indo-European Scenario. But, that scenario is hard to reconcile with the likely origins of the modern Basque not in a migration direct from Southern Portugal where the Bell Beaker phenomena began ca. 2800 BCE, but indirectly from Bell Beaker people who migrated to France and then migrated again to Northern Iberia and Southwest France. Why would language shift happen in Iberia after migrations to France and Britain have already happened?

I Still Think The Non-Indo-European Scenario Is More Probable. In my view the weight of the evidence still supports a non-Indo-European linguistic character for the Bell Beaker people followed by language shift to Celtic languages with only a modest demic component around the time of Bronze Age collapse. Of course, if non-Indo-European Bell Beaker people and Indo-European pre-Celtic and Celtic people ca. 1300 BCE to 500 BCE were very similar in autosomal genetics (and maybe even in mtDNA drawn from related first farmer maternal gene pools enriched in mtDNA H for some reason), it might be easy to underestimate the demic impact of the Bronze Age collapse Indo-Europeans, particularly if some were Bell Beaker Y-DNA R1b men who had been converted culturally to Indo-Europeans while only most were Corded Ware Culture Y-DNA R1a men.

* Central Europeans. It isn't too surprising that areas on the fringe of the Bell Beaker area do not primarily involve demic migration, although it would be interesting to see if there are at least Y-DNA haplogroups or a superstrate percentage of Bell Beaker autosomal genetics. Are Bell Beaker autosomal components at all distinguishable from Corded Ware Culture autosomal components? Did material culture shift in Central Europe also involve a religion and/or language shift? Was it imposed by a thin superstrate or willingly adopted via trade and missionaries as early Bell Beaker theories assumed?

* British Population Replacement. Significant replacement in Britain was foreshadowed by previous results. Other sources have indicated that the First wave Neolithic farmers in England (who arrived, if I recall correctly, around 4000 BCE, had pretty much reverted to hunting and gathering by the time that the Bell Beaker people arrived. I'm curious to know what percentage of the population was replaced and what the gender balance of that replacement was, although a lot (including regional variation in the patterns) can be inferred from existing current British genetics. 

Was Bell Beaker the last big shakeup in British population genetics? It seems as if this was the last really major change in British population genetics with Bronze Age collapse and the arrive and departure of Roman rule having only a modest effect, although some fairly faint Anglo-Saxon and Norman signals seem to be visible in modern British population genetics - of course, given that the putative source of those signals and the putative recipients of them weren't all that different genetically due to the Bell Beaker replacement from more or less the same region ca. 2400 BCE, it isn't too surprising that it is hard to see. I'm also a bit surprised that there isn't an easily visible Punic genetic component in coastal Britain and Ireland, although perhaps it is so consistent across maritime Western Europe in general that it can't be distinguished.

* What About Western Europe? Very little is said about Bell Beaker genetics in Western Europe, despite the centrality of Iberia, France and the Benelux countries to that phenomena.

* What About Lactase Persistence? It would be interesting to know about LP genes over the long transect of time. Was it there from the start or was this a period of active fitness based selection.

* Are Bell Beaker People Just CWC People With Bows And Different Pottery Tastes? Reich's parting sentence suggests that British Bell Beaker people were very similar Corded Ware Complex and Pontic-Caspian steppe people in autosomal genetics. 

Is there any genetic evidence for a male dominated migration from the steppe to Iberia, followed by a new ethnogenesis of the Bell Beaker culture, followed by a secondary expansion?

* By what route to steppe derived Bell Beaker genetics arrive? Slow By Land Or Fast Possibly By Sea? There seems to be a fair amount of Y-DNA R1b phylogeny and modern European Y-DNA R1b haplogroup distribution evidence to support a gradual expansion path of people with Y-DNA R1b and presumably also autosomal steppe ancestry from the steppe to Central Europe and the radiating from there. But, the archaeology and mtDNA seems to support a rapid long distance migration of men with Y-DNA R1b and steppe autosomal genetics to Iberia from Eastern Europe, perhaps by sea, followed by secondary expansion from Iberia as explained in the introductory sentence of the abstract. What can explain this disparity?

Centuries Of Folk-Migration Pre-Ethnogenesis? One conceivable theory would by a 300 years in the wilderness scenario in which a bunch of displaced steppe men seeking their fortunes with Y-DNA R1b (perhaps defeated Yamnaya men) migrate and leave descendants in central Europe (perhaps as wandering raider bands a la the Goths and the Vandals) and then radially until they reach Iberia, but that they don't thrive until they arrive in Portugal which has the metal resources they need, at which point there is Bell Beaker ethnogenesis, possible language shift, and rapid secondary expansion.

Razib Khan makes a similar point about complex models involving potential secondary expansions at his blog:
It would not be entirely surprising if the originators of a cultural complex transmitted it to another group, and then that culture “hitchhiked” on the demographic expansion of the receiving group. A good example would be Roman Catholic Christianity. The Iberians spread it to the New World, along with substantial demographic movement. But the religion itself did not spread to Iberia through migration, but rather cultural shift.
The reference in his post to the Milesians is presumably the the Greek philosophers from Ionia on the Western Coast of Anatolia who brought about a major worldview change in Greek thought in the 6th century BCE (although arguably in that case for the worse). By implication, he suggests that the new paper of Reich and company will change the paradigms of European prehistorians for many years to come with their ancient DNA data as they have already started to do with their Indo-Europeans from the Steppe paper. 


Ryan said...

"The Non-Indo-European Scenario. But, that scenario is hard to reconcile with the likely origins of the modern Basque not in a migration direct from Southern Portugal where the Bell Beaker phenomena began ca. 2800 BCE, but indirectly from Bell Beaker people who migrated to France and then migrated again to Northern Iberia and Southwest France. Why would language shift happen in Iberia after migrations to France and Britain have already happened?"

Why is that contradictory? Why can't an earlier wave be replaced by a later one? If Basques are primarily descended from Bell Beakers, why would that make Bell Beakers IE? I think elite dominance and then back-migration is the simplest explanation.

I also think we're incorrect in assuming R1b is a steppe marker. It seems much more like a WHG marker, and Yamnaya got it from its R1b heritage, where Indo-European would have come with R1a or Q (both absent among WHG). We have R1b hunter gatherers from the other side of the Carpathians with low levels of steppe ancestry to look to.

andrew said...

The assumption that R1b is a steppe marker follows pretty naturally from the fact that R1b-M269 and daughter variants don't appear in Europe until people who have steppe ancestry do and overwhelmingly among people with steppe ancestry. It is absent in all WHG and in all first wave Neolithic people in Western Europe, It is found in Southern steppe folk (the Yamnaya) and their predecessor EHG people. The most basal example of Y-DNA R, in MA-1, was found in eastern Siberia.

R1b may very well not be an IE marker, but it is certainly not a WHG marker.