Not many guys are brave enough to take on Genghis Khan. But then, Genghis never met Hank Greely. Greely, a law professor at Stanford , does a lot of work in genetics and brain science. And he's tired of hearing the tale about Genghis single-handedly (well, "handedly" might not be the precise term) populating the Eastern world. According to the version I quoted yesterday , "8% of males throughout the former lands of the Mongol empire carry the Y chromosome of Genghis Khan."
Not so fast, says Greely:
Here are the facts, as far as we know them. One Y chromosome haplotype is widespread over areas that the Mongols ruled. Genghis ruled the Mongols and had, at least, the opportunity to father many sons, some of whom had similar opportunities. End of facts.
Maybe that's Genghis's Y chromosome, but, as we have no DNA from Genghis (his tomb was hidden) and no certain knowledge of any of his living direct line male descendants, we don't know what his Y chromosome looked like.
Maybe it's the Y chromosome of Genghis's handsome troubadour, or vicious chief of staff, or someone else. We don't know.
And even if it is Genghis's Y chromosome, it's possible none of those now carrying it descended from him. His brothers, paternal uncles, paternal male cousins, etc., all had the same Y chromosome. In fact, if he came from a clan with a lot of males, it probably helped him become the leader. One of the few actual studies showed that 35% of Mongols have this Y chromosome type—is Genghis the cause or the result of that statistic? Who knows?
Do I think there's a good chance that this is Genghis's Y chromosome? Sure, probably as good a chance as anyone and better than most. But how good is that? Who knows. But it's a good story and so it has spread like flu—in part being spread by genetic genealogy companies that are looking for good stories to use that might help convince people to buy their services.
For a more formal version of Greely's critique, see his chapter, "Genetic Genealogy," in Revisiting Race in a Genomic Age , published last year.
Oh, and if you're planning to sue Genghis' estate for your share of the inheritance, don't even think of offering your Y chromosome as evidence. I have a pretty good idea whom the estate will be calling as an expert witness.