J1 developed in the Southern Levant and is likely "Semitic" in origin. It has remained situated primarily in Middle Eastern populations and in Northern African Arab populations. Rare in Europeans, with the exception of Jewish Europeans, who have it at a frequency of 14-18%.
Haplogroup J2 originated in the northern portion of the Fertile Crescent particularly in Anatolia where it later spread into Europe during the Neolithic period (~5,000 years ago)and throughout central Asia, the Mediterranean, and south into India which saw the spread of soil cultivation, crop production and the raising of livestock. This culture of farming and agriculture has since spread much further than the people who developed it although J2 (along with Haplogroup E3b) were likely founders taking a Levantine/Anatolian dispersal route to southeastern Europe.
Haplogroup J2 now has a wide distribution and often high frequency across Iberia, Italy, Turkey, Albania, Greece, Arabic countries and across into India.
J2 has been well studied and can be split into several clades but whose mode of individual distribution is not well understood. Many influences such as Greek and Roman would have played a part.
20% of Askenazi Jews are J2. The Cohen Modal Haplotype (CMH), an STR pattern indicative of the Cohanim (Jewish populations), can be found within haplogroup J2 as with other populations with Mediterranean ancestry. However, because the CMH and both haplogroups J1 and J2 are found outside of Jewish populations, it is not possible to deduce Jewish ancestry from inclusion.
Credit: Definitions for haplogroups is borrowed from both