The Y dna distribution by haplotypes in modern Armenians : dotting the I2-s.
The first chart is based on modern commercial data from FTDNA. It shows the most important branches also known as haplotypes. As You can note, with the exception of R1b-Z2103 the rest of Y dna is quite fragmented. The number of haplotypes that score more than 3% of population is ten. In this list of top 10 the TVC lineage I2-BY423 (also known as Y16419) is in the 9th position. I think based on this chart it's obvious that any Armenian haplotype that score more than 3% can't be labeled as "very low" or "inexistent".
But this is not the whole story. In this top 10 at last 4 haplotypes have a Neolithic - Chalcolithic age ( J2- L25, G2-M406, T-L208, E-M84 ). And current paleogenetic evidence supports their relatively old expansion. Although in some cases they have also younger lineages. Like J2-L25 which has a subbranch L70. It makes the third of L25 and it expanded in Iron Age.
So if we concentrate only on Bronze Age expansions that have more relevance to modern ethnicities then the list will be arranged in a different way.
The main lineage that expanded in Early Bronze Age (Kur-Araxian culture) are the J1-Z1842 and most probably the J2-M92. It's possible that E-M84 also is partly related to KA but there is no direct proof of that theory.
The lineages that expanded in Middle Bronze Age and after are the R1b-Z2103, I2-BY423, J2-FGC15865 ( a lineage related to Van-Urmia culture ) and R1a-Z645 appears predominantly in Iron Age.
There is also a Bronze Agr lineage J1-L862. It's from Levant and Mesopotamia.
They are also lineages that expanded in Iron Age and later but their percentage points do not exceed 1.5-2%. And they are too late to be crucial for the Ethnogenesis. Even though they are important for understanding some aspects of Armenian history.
Returning to I2 in Armenia. The main question is that did it had a dramatic decrease over time given the available paleogenetic evidence?
Well to have an answer to that question one needs to compare apples to apples not to oranges. I mean that modern Armenian Y dna is gathered from a large territory stretching from Cilicia/Sebastia to Caspian Sea/Iran. If we want to understand how the level of I2 changed over time we need to compare data from equal geographic regions.
We don't have detailed Iron Age aDNA from the aforementioned region. But I think it's not hard to imagine that it's very very unlikely that I2 level exceeded 5% in Iron Age historic Armenia and it's large neighbourhoods if a systematic ancient DNA becomes available.
Even more. Inside ancient Republic of Armenia the I2 was present in high levels only in Sevan basin sites. See the second chart (Noratus, Lchashen, Sarukhan ) Karashamb in Kotayk is close to Sevan. If we look at Urartian era samples that do not have any aDNA from Sevan basin then we see a completely different picture. See the third chart. Offcourse 20 Y dna is a small sample size. But we can reproduce a similar result for LBA-EIA period if we remove all Sevan basin sites.
In any case it's obvious that in modern RoA territory there was an important change of Y dna distribution in Iron Age. I will dedicate a special thread to this subject. Obviously both I2 and R1b decreased but given current data we can say that while they decreased in RoA they must have increased in some other regions of historic Armenia. Otherwise how we would have 3% of I2 from large territory stretching from Anatolia to Iran?
In conclusion the current Armenian Y dna is dominated by haplotypes that expanded Bronze Age. Initially they had localized peaks in certain regions. But overtime they diffused out of their peak regions and modern distribution became more homogenous. I2 is not a special case in this story. The only thing that it has more limited geographic peak than R1b which in most likelihood expanded over larger regions.