R1a1a Ashkenazi Levites belong to Y-DNA haplogroup R1a, which is one of the most common haplogroups throughout Europe and Western Asia and on the Indian Subcontinent.
Today, R1a is the dominant Y-DNA haplogroup in parts of Eastern and Central Europe, including Poland (57.5%), Belarus (51%), Russia (46%), Ukraine (45%), Slovakia (41.5%), Latvia (40%), Lithuania (38%), Slovenia (38%), the Czech Republic (34%), Estonia (32%), Moldova (30.5%), and Hungary (29.5%). R1a is also quite common in Iran (16.5%), the portion of Kurdistan that is in Turkey (16%), and North Iraq (Kurdistan) (11.5%), as well as in Southern Asia. Not surprisingly, R1a’s distribution does not coincide with national boundaries; a distribution map shows that there are regions in south-central Poland and on the Ukraine-Russia border where the concentration of R1a exceeds 60%.
According to Klyosov and Rozhanskii, “haplogroup R1a arose in Central Asia, apparently in South Siberia or the neighboring regions, such as Northern and/or North-western China, around 20,000 years before present.” Thereafter, R1a men began migrating to the west, across the Himalayas, arriving in the Iranian Plateau and Asia Minor between 9,000 and 10,000 years ago. By 8,000 to 9,000 years ago, “they arrived in the Balkans and spread westward over Europe and to the British Isles.” By 4,600 to 4,800 years ago, R1a1 men had moved to the Russian Plain. From about 3,600 to 4,200 years ago, R1a1 men spread to the south, east, and southeast, into Anatolia, Iran, India, and south Siberia. The latter migrations are associated with the proto-Indo-European language, the forebear of the Indo-European languages. A. Klyosov & I. Rozhanskii, Haplogroup R1a as the Proto Indo-Europeans and the Legendary Aryans as Witnessed by the DNA of Their Current Descendants, Advances in Anthropology, Vol. 2, No. 1, 1-13 (2012).
Rozhanskii and Klyosov (reversing their billing for a second article) have identified 38 branches of R1a haplogroups that currently exist in Europe or that migrated from Europe to areas in the east, south, or southeast between 4,500 and 6,000 years ago. Rozhanskii and Klyosov describe three principal downstream subclades of R1a which split from each other about 6,000 to 7,000 years ago: (1) R1a-L664 (the North-Western branch); (2) R1a-Z93 (the South-Eastern branch); and (3) R1a-Z283 (the Eurasian branch). I. Rozhanskii & A. Klyosov, Haplogroup R1a, Its Subclades and Branches in Europe during the Last 9,000 Years, Advances in Anthropology, Vol. 2, No. 3, 139-56 (2012).
According to Rozhanskii and Klyosov, the Z93 branch is comprised of three downstream branches: (1) R1a-Z94; (2) R1a-L342.2; and (3) R1a-L657. About 98% of R1a-Z93 men belong to the R1a-L342.2 cluster, which Rozhanskii and Klyosov divide into a Bashkir branch, a Kyrgyz branch, and a Jewish branch (referred to on this website as R1a1a Ashkenazi Levites); these three branches share a common direct male ancestor living about 4,800 years ago. Rozanskii and Klyosov find that the common direct male ancestor of R1a1a Ashkenazi Levites lived 1,300 years ago, plus or minus 150 years, “as part of a lineage with a common ancestor living 4475 ± 400” years ago. I. Rozhanskii & A. Klyosov, Haplogroup R1a, Its Subclades and Branches in Europe during the Last 9,000 Years, Advances in Anthropology, Vol. 2, No. 3, 139-56 (2012).
 The Eupedia website compiles percentages, by haplogroup, for countries in Europe and some countries in the Middle East. In some countries, the current sample size is relatively limited; additional test results are likely to change the haplogroup proportions reported on the website.
Professor J. Douglas McDonald has prepared a map showing, with pie charts, the believed proportions of Y-DNA haplogroups among various populations as of the year 1500.