Let's compare the Georgian Y dna with Armenian.
The most frequent haplogroup in Georgia is the G2a1. The Caucasian subclade of G2a1.
G2a1-Z6653 - 24% in Georgia
G2a1-Z6653 - 0.5% in Armenia
This Y dna was a minor (rarely occuring) Neolithic farmer lineage from Fertile Crescent. The most probable homeland is the north Mesopotamia or Zagros. Indeed the oldest G2a1 that we have is from South Zagros Late Neolithic. From there it moved to Central Asia with other Iranian Neolithic farmers. We have one case in BMAC (Uzbekistan) Bronze age culture. Also one case in a Medieval burial from Kyrgyzstan. And another in Avar nomadic burial.
Another branch of G2a1 Z6653 moved to South Caucasus. It is in Caucasus that this haplotype had a successful founder effects. One important expansion occured at Middle Bronze age (probably after Kur-Araxian culture 2400bc) and another later in antic hellenistic? period.
G2a1 was found in Koban Iron age culture in North Caucasus. So at some point in Late Bronze age it crossed Caucasus and moved to North also.
Today the highest levels of G2a1 can be found among Ossetians ~65% and Svans ~80%.
It is not important what language it was speaking in deep Neolithic past. But the extremely high levels among Svans implies that this haplotype was present in Proto Kartvelian community and expanded a lot with it. Linguists propose a MBA divergence for Svans from Proto-Kartvelian so here linguistics and genetics are in accordance.
Judging by the data we have the Proto-Kartvelian community was probably living in central or central-western parts of modern Georgia. So should they had an important expansion toward historic Armenia (Erzrum region) then we would expect an important presence of G2a1 among Armenians. But it is not the case.
Now let's look other haplotypes.
The J2-Y12379 or SK1313 found in Kotias.
J2-Y12379 - 6.7% - Georgia
J2-Y12379 - 0.5% - Armenia
This haplotype had an old presence in Caucasus. It was found in Mesolithic (7500bc) Georgia in Kotias Klde site. Later with the arrival of farmers it's numbers probably declined. But it is still frequent in Georgia. Once more if we had an important migration from Georgia to historic Armenia one would expect to see them in Armenia. But it is not the case.
Here we must keep in mind that not all cases of SK1313 / Y12379 found in Armenia are from Georgia. We don't have Mesolithic data from ancient Armenia. There is little doubt that the same haplotype was present among ancient Armenian hunters. I did this comparison to emphasize once more how different are the proportions of various Y dna in this two neighbouring nations.
(to be continued)