Did The Yamnaya Die Or Run?

Razib Khan has tweeted the biggest story of the ASHG 2015 Conference (key points in bold):

@iosif_lazaridis revision of paper @mathiesoniain with more ancestry stuff on biorxiv soon
@iosif_lazaridis [Neolithic Anatolian] mtDNA look familiar to EEF. Y mostly G2a2. also J2 H and I at low frequency. C1 too
@iosif_lazaridis anatolian neolithic close to EEF on pca. but EEF shifted toward WHG #ASHG15
@iosif_lazaridis anatolian neolithic different from modern anatolian and se europe populations.
@iosif_lazaridis eurasian steppe, population transect done. 5,500 to 1,200 BC. author told me some R1a1a possibile stuff here yesterday
@iosif_lazaridis indo-european steppe = EHG + near eastern. new data eneolithic samara. 75% EHG ancestry. 25% "armenian" 5,200 to 4,000 BCE
@iosif_lazaridis poltavka people 3000 to 2200 BC basically like yamnaya. 50% EHG and 50% armenian-like. then srubnaya different.
@iosif_lazaridis srubnaya 2/3 yamnaya 1/3 middle neolithic european
@iosif_lazaridis yamnaya/poltavka went from R1b to R1a in the srubnaya period. z93 group found on bronze age steppe samara (s asian R1a)
@iosif_lazaridis there was back migration of EEF to the steppe after the initial yamnaya migration.

Via Eurogenes.

This is a huge new set of facts with potentially profound implications for how we understand European history.

In the span of a few centuries, starting around 2200 BC, a Y-DNA R1b dominated population, the Yamnaya and their descendants the Poltavka, were replaced in the southern part of the European steppe (or at least the men were) by a Y-DNA R1a dominated population with strongly overlapping autosomal genetic profiles, the Srubnaya.

One possibility is that the Yamnaya men were slaughtered by the Srubnaya men who may have assimilated some of the Yamnaya women, in a scenario mirroring that of the battles described in the Biblical Book of Numbers.

But, something remarkable happens in Western Europe right around the time that Y-DNA R1b men disappear from the southern part of the European steppe.  All of the sudden, Y-DNA R1b that was virtually absent from Western Europe rapidly becomes the predominant Y-DNA haplogroup of Western Europe and there are substantial shifts in the mtDNA mix of Western Europe.

The distribution of Y-DNA R1b sub-haplogroups in Europe and their phylogenetic relationship, suggests a route from East to West of Y-DNA R1b carriers from the European steppe to central France and from their spoke-like migrations in all directions.

The insight in today's talk provides a push factor - the Srubnaya (whom Davidski at Eurogenes describes as more militaristic and technologically advanced than the Yamnaya).  A collapse of Western European first wave Neolithic farming societies as a consequence of the 4.2 kiloyear event, meanwhile, may have left their societies in turmoil and collapse (including population collapse) leaving a political vacuum and slack in food production capacity once the event's harsh climate abated, into which the Yamnaya people, participating in a folk migration much like that of the "migration period" travels of Germanic tribes like the Goths, Visigoths, and Vandals in the Dark Ages, into Western Europe.

The Yamnaya were basically steppe pastoralists, which is to say, herders.  Faced with a potentially deadly military adversary, farmers stand their ground upon which they rely to survive, even if the consequences are dire.  But, herders in a culture that exults cattle and bulls rather than corn and wheat, don't have to suffer the consequences of standing and fighting against opponents who may be superior to them militarily, or just more determined.  They can run, as an entire community, taking the cattle and horses that provide the source of their wealth with them, at a lower cost that does not have to be paid in blood.

And, wouldn't it stand to reason that people in a cattle herding society would be more likely to have LP genes that allow them to drink cow's milk as adults which was gradually selected for over thousands of years, which they would bring with them in their genes to their new homeland, than a society of farmers would be to suddenly develop this gene through explosive and rapid natural selection?

And, given that these people could have been ancestral to Europe's Basque (who have high frequencies of Y-DNA R1b, has traditions that place an emphasis on cattle, who arrives in their current relict homeland in my view from France, have high levels of the LP genes, and speak a language that is distinct in being ergative, just like the language of the Georgians with whom the Yamnaya's non-Eastern Hunter-Gatherer autosomal genetic component shows strong affinity), it is highly plausible that their language (and hence Basque and other Vasconic languages) was an offshoot of the Kartvelian language family, possibly after creolization with Eastern Hunter-Gatherer languages that also contributed strongly to the Proto-Indo-European language, and with substrate influences from whatever first farmer Neolithic language was spoken in Western Europe before they arrived.

Razib recently hypothesized that Proto-Indo-European and Afro-Asiatic were hunter-gatherer substrate languages that were adopted by Early European farmers who admixed with them.

But, I don't think that scenario is plausible.  When hunter-gatherers and farmers collide, usually, the farmer's language prevails (see, e.g., Japan, where the rice farming Yayoi's language became the backbone of the Japanese language, but almost no words from the hunter-gather Jomon who spoke a language in the same language family as the Ainu made it into Japanese, despite the fact that something like 40% of the genetic ancestry of the Japanese is Jomon including a large share of the male Y-DNA), although sometimes there are some substrate influences that shape the superstrate language dialect that comes to be spoken in the blended community.

The alternative, which usually happens when the superstrate population is greatly outnumbered by a substrate population and the two populations have no linguistic common ground, is the development of a creole language, which Indo-European shows some elements of (or at a minimum simplification of the language driven by a large community of second language learners in the society), and which has been suggested on archaeological grounds by the mixed ethnicity communities that existed around the time and place that PIE came into being, long before ancient DNA tools were available.

The lexical similarities that Maju recently discovered between both Proto-Indo-European and Nilotic Nubian languages may very well be real, but he may have misapprehended the direction of the connection.  Perhaps, the lexical similarities in Nilotic Nubian may be the result of Neolithic migrants to Africa who arrive via the Sinai and the Nile bringing the words of their language, related to Kartvelian, with them, where the existing residents adopted them, rather than the other way around.

The Yamnaya folk migration hypothesis which I have just sketched out, which is strongly motivated by powerful ancient DNA evidence, has the potential to pull together myriad puzzle pieces of European prehistory in a single stroke.

It doesn't answer all of the questions.

What connection did the Bell Beaker culture have to the Yamnaya?

Is there any archaeological evidence to support this hypothesis?  And, if there was such evidence, what would we expect it to look like?  Is the lack of evidence of an apocalyptic war that destroyed the vast majority of Yamnaya men itself evidence favoring this hypothesis?  Before dismissing this conjecture for a lack of archaeological evidence, at a minimum, the archaeological evidence should be reviewed with fresh eyes informed by this hypothesis.

Did other members of a Yamnaya diaspora make their way to Western Anatolia (perhaps Troy I?) or Crete?

Finally, when did the migration(s) start?

Perhaps the Poltavka people are the Yamnaya who held out on the southern European steppe longer, but the transition from the Yamnaya culture to the Poltavka culture was a product of the disruption caused by the folk migration of the rest of the Yamnaya to Western Anatolia, Crete and Western Europe.  A 3000 BCE start date for these migrations is a better fit to the archaeological culture that could potentially reflect their arrival in their putative destinations.

This also illustrates the fact that dying and running are not necessarily mutually exclusive possibilities.  Perhaps some of the Yamnaya ran in various directions, giving rise to the various European cultures in which Y-DNA R1b is common, while other Yamnaya stood their ground, becoming the Poltavka, and ultimately died at the hands of Y-DNA R1a dominated peoples from the northern European steppe who slaughtered the Poltavka and took their land.

Fortunately, it is likely, given the stunning improvements that have been made in ancient DNA extraction, that these are questions to which the answer probably isn't, "we may never know." Instead, stay tuned.  More answers seem to lurk around every corner.