The Caucasus is the Americas of Western Eurasia: Intragroup-Genetic and Linguistic Diversity Are Inversely Correlated
Dienekes continues to refute himself and adopt my ideas. In his latest ADMIXTURE experiment he announces
“The most salient point about this analysis is the central position of the Caucasus component vis-a-vis the others, consistent with my womb of nations theory. Not only do all West Eurasian components (except the North European) appear substantially “Caucasus” in this analysis, but the Caucasus component itself shows links with four others.It could be argued that these results represent a confluence of peoples from all over West Eurasia into the highlands of West Asia where the Caucasus component is modal. But, the Caucasus region is arguably the most linguistically diverse in West Eurasia, and many of its languages do not appear to have come from elsewhere.”
It’s good to see that, under the weight of my counter-arguments (see here, with further links), he finally admitted that modern West Eurasian populations have a “Caucasus,” and not a “West Asian” component. He originally devised the latter label to help propagate the putative genetic proof for the Anatolian theory of Indo-European origins until that Titanic of an idea hit the an iceberg of facts.
In addition it is good to see that Dienekes finally followed my judgment on the formative role of the Caucasus in the history of Western Eurasia, which was based on the factor of high linguistic diversity in that area. Back in September of 2011, Dienekes still thought that high intragroup genetic diversity is a sure indication of a population’s age. And that high linguistic diversity is misleading and epiphenomenal. He wrote,
“The Caucasus is one of the areas of Eurasia with the highest linguistic diversity, but as was shown in the recent Yunusbayev et al. paper, its population is fairly homogeneous in the Eurasian context.”
To which I responded:
“So, genetic homogeneity is not a sign of recency. Works for the Caucasus, works for America, works for Papua New Guinea (all ancient refugias with lots of selective constraints that drive genetic diversity down but doesn’t affect languages), works for Neandertals (no data on languages).”
We can now add Hadza to this list of examples: Hadza display reduced levels of intragroup genetic diversity and higher levels of linkage disequilibrium compared to other Africans but it is the most divergent branch of the Khoisan family. Although the reality of the Khoisan family is being contested by linguists, Hadza and South African Khoisans share the same autosomal component giving additional weight to the linguistic argument for Hadza divergence.
While he adopted my view on the Caucasus, Dienekes continues to stubbornly distort the findings of his own Dodecad experiments when it comes to the New World. The Caucasus is the Americas of the world: American Indian populations have the highest linguistic diversity, as measured by the number of independent stocks, but depressed intragroup genetic diversity.
Notably, there is no migration out-of-Africa on this graph (Africans achieved their diversity by enjoying the snowball effect of different admixture components), and Amerindians are a genetically “pure” or “homogeneous” (hence not “diverse”), long-term isolate. At the same time, American Indians are exceptionally diverse linguistically, while Africans have low-to-moderate linguistic diversity. The relationship of the Amerindian component to the Siberian component is couched in contradictory thinking: on the one hand, Dienekes claims that Amerindian is “wholly Siberian”; on the other hand, “Siberian appears East Asian + slice of Amerindian.” Logic is not Dienekes’s forte. If we re-write the latter statement to incorporate the former one, we arrived at a nonsensical “Siberian appears East Asian + Siberian.”
Dienekes is clearly trying to sweep under the carpet what is the simplest, most illuminating reading of his own data, namely that Amerindian supplies the founding component to the Old World populations, naturally via the closest geographical area, Siberia, and along the traditional Beringian pathway, without receiving any gene flow back. The latter is again very natural as the New World is hardly accessible from the Old World and its geography prevented populations from a genetic back-and-forth. What several commenters on Dienekes noted is that the Amerindian component (but not the Siberian component) is also present in “Atlantic-Baltic” populations.
This suggests that the founding genetic contribution from the New World to the Old World got parceled out along what was likely a Circumarctic route into the founding East Eurasian and a founding West Eurasian components. Consequently, using brighter colors and better logic than Dienekes, his data yields to the following most parsimonious graphical interpretation (without indicating strength of gene flow):
This is essentially the model I presented to Joanna Mountain back in the late 1990s-early 2000s: the direct heirs of the original small Pleistocene demes survived in the New World but stayed outside of the massive population expansion and gene flow that has affected Old World populations after the original founding genes had been transplanted from the New World into the Old World. The timing of this insight could not have been worse, as out-of-Africa was enjoying a huge rise in popularity. But, as it often happens in science, new data comes to the rescue of dismissed alternatives.