Expansion of the R1a-Y2619 Ashkenazi Levite Population

[The below analysis was prepared in about 2013, at a time when it was believed that the R1a-Y2619 Ashkenazi Levite progenitor lived about 1,000 years ago and that half of the R1a-Y2619 Ashkenazi Levite population was descended from a single man who lived about 600 years ago. More recent analyses demonstrate that that as of the start of the 15th century there were likely hundreds if not thousands of R1a-Y2619 Ashkenazi Levites. Accordingly, this page is outdated; it is included as a matter of historical interest.]

As of the start of the 15th century, there were only about 50,000 Ashkenazi Jews; by the start of the 19th century, there were about 5,000,000 Ashkenazi Jews. See G. Atzmon et al., Abraham’s Children in the Genome Era: Major Jewish Diaspora Populations Comprise Distinct Genetic Clusters with Shared Middle Eastern Ancestry, Am. J. Hum. Gen. 86:850 (2010). This is a hundredfold increase.

Assuming for ease of analysis that the proportion of R1a-Y2619 Ashkenazi Levites in the Ashkenazi population at the start of the 15th and 19th centuries was the same as the current population estimated in the 2003 paper by Behar et al. (approximately 2% of the total population), that influx from Sephardi and Mizrahi populations did not increase the Ashkenazi population between the start of the 15th century and the start of the 19th century, and that the R1a-Y2619 Ashkenazi Levite progenitor living at the start of the 15th century was the ancestor of 50% of R1a-Y2619 Ashkenazi Levites (as suggested by initial STR analyses posted on this website), that man would have had about 25,500 direct male descendants (and 50,000 descendants born to a father on his direct male line) as of the start of the 19th century.

Assuming for ease of analysis that the proportion of R1a-Y2619 Ashkenazi Levites in the Ashkenazi population at the start of the 15th and 19th centuries was the same as the current population estimated in the 2013 paper by Rootsi & Behar et al. (approximately 13% of the total population), that influx from Sephardi and Mizrahi populations did not increase the Ashkenazi population between the start of the 15th century and the start of the 19th century, and that the R1a-Y2619 Ashkenazi Levite progenitor living at the start of the 15th century was the ancestor of 10% of R1a-Y2619 Ashkenazi Levites (as suggested by more recent STR and SNP analyses posted on this website), that man would have had about 32,500 direct male descendants (and 65,000 descendants born to a father on his direct male line) as of the start of the 19th century.

Such reproductive success is mathematically feasible, assuming that in the early generations R1a-Y2619 Ashkenazi Levite men had a substantial number of sons who in turn had a substantial number of sons.

[As noted above, there were hundreds if not thousands of R1a-Y2619 Ashkenazi Levites as of the start of the 15th century. Accordingly, the size of the R1a-Y2619 Ashkenazi Levite population as of the start of the 19th century is not disproportionate to its size as of the start of the 15th century.]