“For years, the favored recipe for making a modern European was this: Start with DNA from a hunter-gatherer whose ancestors lived in Europe 45,000 years ago, then add genes from an early farmer who migrated to the continent about 9000 years ago. An extensive study of ancient DNA now points to a third ingredient: blood from an Asian nomad who blew into central Europe perhaps only about 4000 or 5000 years ago. This third major lineage originated somewhere in northwestern Asia, perhaps on the steppes of western Asia or in Eastern Europe. This is a “ghost lineage,” because no pureblood member of this group survives today.”
http://www.sciencemag.org/content/345/6201/1106.short//cdn.embedly.com/widgets/platform.js