About four years ago the genome blogger Dienekes Pontikos published a post, The womb of nations: how West Eurasians came to be. The argument was that the genetic variation we see around us across western Eurasia and northern Africa has its ultimate roots in the the structure that was extant in the ancient Near East, near to the zone of initial agricultural innovation in the hills above the modern nations of Syria and Iraq. It was similar to the thesis of Peter Bellwood in First Farmers: The Origins of Agricultural Societies. The model as outlined by Dienekes suggested that local substrate was absorbed as these initial agriculture societies rapidly swept outward from their initial focal zone. In the broadest strokes I do think that he, and Bellwood, were correct from what we now know.
Ancient DNA in Europe strongly indicates massive replacement. But, there is also suggestion of admixture with the local substrate. And, unlike the stylized model of Bellwood, it seems that there were multiple migrations after the initial pulse which reshaped the genetic and cultural landscape of human societies in the wake of agriculture. Here is the abstract for Lazaridis et al. at ASHG:
It has hitherto been difficult to obtain genome-wide data from the Near East. By targeting the inner ear region of the petrous bone for extraction [Pinhasi et al., PLoS One 2015] and using a genome-wide capture technology [Haak et al., Nature, 2015] we achieved unprecedented success in obtaining genome-wide data on more than 1.2 million single nucleotide polymorphism targets from 34 Neolithic individuals from Northwestern Anatolia (~6,300 years BCE), including 18 at greater than 1× coverage. Our analysis reveals a homogeneous population that is genetically a plausible source for the first farmers of Europe in the sense of (i) having a high frequency of Y-chromosome haplogroup G2a, and (ii) low Fst distances from early farmers of Germany (0.004 ± 0.0004) and Spain (0.014 ± 0.0009). Model-free principal components and model-based admixture analyses confirm a strong genetic relationship between Anatolian and European farmers. We model early European farmers as mixtures of Neolithic Anatolians and Mesolithic European hunter-gatherers, revealing very limited admixture with indigenous hunter-gatherers during the initial spread of Neolithic farmers into Europe. Our results therefore provide an overwhelming support to the migration of Near Eastern/Anatolian farmers into southeast and Central Europe around 7,000-6,500 BCE [Ammerman & Cavalli Sforza, 1984, Pinhasi et al., PLoS Biology, 2005]. Our results also show differences between early Anatolians and all present-day populations from the Near East, Anatolia, and Caucasus, showing that the early Anatolian farmers, just as their European relatives, were later demographically replaced to a substantial degree.
A somewhat different abstract was submitted for a meeting in Germany:
We study 1.2 million genome-wide single nucleotide polymorphisms on a sample of 26 Neolithic individuals (~6,300 years BCE) from northwestern Anatolia. Our analysis reveals a homogeneous population that was genetically similar to early farmers from Europe (FST=0.004±0.0003 and frequency of 60% of Y-chromosome haplogroup G2a). We model Early Neolithic farmers from central Europe and Iberia as a genetic mixture of ~90% Anatolians and ~10% European hunter-gatherers, suggesting little influence by Mesolithic Europeans prior to the dispersal of European farmers into the interior of the continent. Neolithic Anatolians differ from all present-day populations of western Asia, suggesting genetic changes have occurred in parts of this region since the Neolithic period. We suggest that the language spoken by the homogeneous Anatolian-European Neolithic farmers is unlikely to have been the same as that spoken by the Yamnaya steppe pastoralists whose ancestry was derived from eastern Europe and a different population from the Caucasus/Near East [Haak et al. 2015], and discuss implications for alternative models of Indo-European dispersals.
And now, David has a post up, Yamnaya’s exotic ancestry: The Kartvelian connection. You can read the post yourself, but he presents TreeMix results which strongly imply that the Near Eastern gene flow into the Yamnaya population derives from one with a relationship to modern Kartvelian groups, the most prominent of which are Georgians. This is not entirely surprising. I’ve seen similar things, though I’m not sure what to think of this. Going back to Dienekes’ post he suggests that “It is, perhaps, in the ancient land of the Colchi, protected by the Black and Caspian seas, and by tall mountains on the remaining sides, that something resembling the ur-population survived.” That is, the people of the trans-Caucasian region may preserve elements of the deep ancestral heritage of the Middle East which was to some extent effaced by later migrations. I have some Assyrian genotypes, and this population has strong affinities with Armenians and Georgians. Additionally, I believe that much of the west Eurasian heritage in South Asians is from this same region and source. In Genetic Evidence for Recent Population Mixture in India the authors note that “For all 45 Indian groups on the Indian cline…we find that Georgians along with other Caucasus groups are consistent with sharing the most genetic drift with ANI [Ancestral North Indians -Razib].” Of course in South Asia there was a second intrusion of this sort of ancestry, but in this case as part of the admixed compound brought by Indo-Europeans, who interleaved Near Eastern, ancient European, and Central Asian, all in one.
There are two elements here which need to be noted. First, a genetic one in regards to the Middle East. In Europe over thousands of years the heritage of the first farmers waned, as that of the hunter-gatherers experienced some resurgence, and eventually the Indo-Europeans from the steppe overran vast territories. In the Middle East analogous groups which expanded out of the ancient hillocks and swept south were overwhelmed by a later Arabian reflux. These are perhaps prefigured by the drifting of Amorites into the cities of ancient Mesopotamia 4,000 years ago, and more recently the arrival of Arabs who had been outside of the limes of civilization into the worlds of eastern Rome and western Persia.
Finally, this is about the nature of culture and the advantage which a particular toolkit does, or doesn’t, provide a people. The rollover of European hunter-gatherers, or the fact that “Ancestral South Indians” (ASI) don’t exist in pure unadmixed form, point to the advantages which a fully elaborated agricultural cultural system provided the farmers. But, during the initial stages of the development of this toolkit it does not seem that there was any particular advantage to single group in a narrow delimited zone. To be more concrete, the linguistic diversity of the Caucasus region, or what we see and know from the edges of history in the Near East, may be close to the reality of the period of the early Neolithic in the Near East. Different polities with radically different languages, and likely divergent genetics, were all crystallizing the new lifestyle in a cheek by jowl fashion in the hills between the Tarsus and Zagros mountains. At some point though the system became powerful enough that it was portable and extendable in space. Rather than engaging in inter-group competition against populations which were comparable, the most successful route was to expand outward into the vast “unoccupied” zones of hunter-gatherers.
Because of the nature of climate west and east migrations were probably easiest and more rapid. Likely this resulted in a near total translocation of the ancestral cultures on far shores or distant horizons. But as the groups pushed north or south the agricultural toolkit was less well suited, and so synthesis with the native substrate was necessary. I believe that Indo-European and Afro-Asiatic may both be language families of hunter-gatherer populations who absorbed migrating farmers into a radically different ecology where the competitive playing field was much more level than in the initial zone of expansion.