Explanation: Of the many horse-riding nomadic tribes of Eastern Europe, Central Asia, and the Mongolian Plateau, almost all have interacted and intermarried to a much greater degree than sedentary societies of the same period. This is largely because travel is much easier when you’re on horseback, and especially when you aren’t tied down to a cultivated fields, or a house! A tent is good enough for my forefathers; it’s good enough for me! This allows a much wider range of marriage candidates to select from than some sedentary farmer restricted to the five nearest villages.

For that reason, you see some really interesting cultural fusions, and a vast array of phenotypes amongst nomadic peoples of the region - famously, Genghis Khan of the Mongols had reddish hair and green eyes according to one account (and his son, Ogodei Khan, in a posthumous portrait) both traits still seen (albeit very rarely) in modern Mongolia!