http://en.wikipedia.org/wiki/Mongol_Empire#Legacy
Note also
'The influence of the Mongol Empire may prove to be even more direct Zerjal et al. [2003][166] identify a Y-chromosomal lineage present in about 8% of the men in a large region of Asia (or about 0.5% of the men in the world). The paper suggests that the pattern of variation within the lineage is consistent with a hypothesis that it originated in Mongolia about 1,000 years ago. Such a spread would be too rapid to have occurred by diffusion, and must therefore be the result of selection. The authors propose that the lineage is carried by likely male line descendants of Genghis Khan, and that it has spread through social selection.'
which means a similar cause may exist for the distribution of Y chromosome I1
http://en.wikipedia.org/wiki/Haplogroup_I_%28Y-DNA%29
http://en.wikipedia.org/wiki/File:Haplogroup_I.png
Torsten