A 2008 Paper written by Nasidze et al, Close Genetic Relationship Between Semitic speaking and Indo-European speaking Groups in Iran, works to demonstrate that geography plays a much stronger role than language in determining genetic relatedness. The paper focuses on comparisons between the Bakthiari, an indo-european speaking population of Iran and Iranian Arabs. The Haplotype frequency table quickly demonstrates that the level of M172, Haplogroup J2 is fairly evenly distributed througout Iran’s geography and the population groups studied. In fact, it is the most common Haplogroup found in Iran overall and in the above listed study, present in 28% of Iranian Arabs and 25% of the Bakthiari. A full table of the haplogroup frequencies can be viewed here.
While there are some differences with respect to Haplogroup G, paragroup F* which includes J1 (M267) and Haplogroup T (M9), the authors go on to state:
The Iranian Arab group shows close affinities with the Bakhtiari and other Iranian Indo-European-speaking groups for both mtDNA and the Y chromosome. In fact, for both mtDNA and theYchromosome, all of the Indo-Europeanspeaking and Semitic-speaking groups from West Asia exhibit generally low levels of differentiation (i.e. Fst values are less than 0.05). The significant correlation between mtDNA and NRY Fst values, as shown by the Mantel test, further indicates that there are no substantial differences between patterns of mtDNA and NRY variation in this region of the world. The lack of significant differentiation between west Asian Semitic-speaking and Indo-European-speaking groups indicates that language has not been a substantial barrier to gene flow in this part of the world.
Iran shows some of the highest levels of Haplogroup M172 in the world. When one factors in the population of Iran, it may be one of the most populous countries of men bearing the mutation defining Haplogroup J2. But did Haplogroup J2 originate in Iran? This topic is far more complicated and most sources simply indicate its origin as the Northern Portion of the Fertile crescent which could include the northern Levant, Anatolia, Syria, Iraq or Iran. Certainly many subclades of Haplogroup J2 have likely developed outside Iran. Reguiero et al typed their DNA samples in Iran for numerous subclades of J2 which were not found to be present including M137, M158, M163, M280, M318, M319, M321, M339 and M340. These subclades more likely developed and spread from another area of the Near East. Thus Iran is likely not the source region for these particular subclades but could still be one of a few geographical regions of origin for some of the earliest M172 bearing men.