Because so many Turkish-people today claim to be a descendant of Oghuz Khan, male members of the Amucalar, descendants of Gündüz Gazi, the older brother of "Osman I, tested their Y-DNA. Genetic history of the Turkish people, shows that the common ancestor "Ertuğrul", belonged to haplogroup: R1a=6.9% - Typical of Central Asian, Caucasus, Eastern Europeans and Indo-Aryan people.

http://www.ysearch.org/search_view.asp?uid=XWBWW&viewuid;=FTEMF&p;=1