I had previously studied the distinctiveness of Caucasus populations, and now I have added Turks, Cypriots and populations from further West. I am still not satisfied with my Balkan samples (I have 2 Slovenians, 2 Serbs and 1 Bulgarian), so I encourage Balkan participants to contact me for possible inclusion in the Project.
When I turned to ADMIXTURE, a little mystery emerged, for which I have currently no explanation:
Two main components emerged, a light blue "Italo-Balkan" one that seems deficient in West Asia, and red "Cypriot" one that is deficient in West Balkan Slavs and the Caucasus. The three Caucasus populations, each form their own distinctive cluster (green, yellow, blue), and a magenta low-frequency component emerges at K=6, which is why I stopped the analysis at this K. Results for K=5 were similar, minus this low-frequency component.
Here is the big puzzle: my Bulgarian, 2 Serbs, 2 Slovenians, all show unambiguous membership in the green "Lezgin" cluster. Out of all the Caucasus components, this is the only one that seems to have a Balkan connection. While one could argue that this might reflect Neolithic farmers, as it has been argued that they spoke a North Caucasian language, the same "Lezgin" component is insignificant in Greeks and Mixed-Greeks, Southern Italians/Sicilians and Italian (other).
Is this some signal of a population that once inhabited the northern arc of the Black sea, from the Balkans to the Caucasus? This might find some support in the possession by both Lezgins (and Balkan Slavs) of a "North European" component, but the Adygei, who similarly possess such a component show no special affinity with Balkan Slavs. Below is the Lezgin K=10 portrait:
If anyone has any (pre)-historical scenario that might account for this unexpected affinity, feel free to write to me or leave a comment.