Towel Day, Genghis Khan, and Genetic Genealogy

OK, so this post was supposed to be done May 25^th, Towel Day,[1] in honor of the fabulous Douglas Adams. I don’t feel too bad about it not posting that day because, in his own words:

I love deadlines. I like the whooshing sound they make as they fly by.[2]

Towel Day gets its name from The Hitchhikers Guide to the Galaxy (aka The Guide), the first book in the 6-part trilogy of the same name, which states:

A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value–you can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble sanded beaches of Santraginus V…

You get the idea.

Also in The Guide is Mr. L. Prosser. Definitely not as well known as the towel bit or even the Babel fish, but The Guide has this to say about him:

Mr. L. Prosser was, as the say, only human. In other words he was a carbon-based bipedal life form descended from an ape. More specifically he was forty, fat and shabby and worked for the local council. Curiously enough, though he didn’t know it, he was also a direct male-line descendant of Genghis Khan, though intervening generations and racial mixing had so juggled his genes that he had no discernible Mongoloid characteristics, and the only vestiges left in Mr. L. Prosser of his mighty ancestry were a pronounced stoutness about the tum and a predilection for little fur hats.

Holy Moly! My brain hiccuped. The Guide was originally written as a radio program in 1978 and published the following year. Genetic testing to allow Mr. Prosser to identify this lineage probably wasn’t even a glimmer in someone’s eye. But, someone’s eye did eventually glimmer and with the ‘aha moment’ that the Y-chromosome was passed along patrilineal lines from father to son, the route to ‘genetic Adam’ was scouted. Now, I first heard about the “Genghis Khan” genetic test at this year’s National Genealogical Society conference. So, with this little brain hiccup, I went digging to find out more about it.

The Genetic Legacy of the Mongols was published in The American Society of Human Genetics in March 2003[3]. In this article the authors, Zerjal et. al. identified a Y-chromosomal haplotype with an unusually widespread distribution in Asia and came to the conclusion that natural selection or chance couldn’t successfully account for the frequency. However, when they overlaid maps of the populations exhibiting this haplotype and the empire of Genghis Khan at the time of his death…eerie correlation. Based on the ‘it’s good to be the king’ theory, they attributed the distribution to Genghis Khan and his male-line dynasty and a marketing tool for genealogical testing companies was born.

So, what’s to be learned from this? Well, one thing you notice when reading the paper is that there is no direct evidence as we don’t exactly samples of Genghis Khan’s DNA lying around to analyze. So, like in genealogy, Zerjal et. al. turned to indirect evidence in reaching their conclusion and addressing the pieces that don’t quite fit. In this case, that unfitting piece is a population who lives outside the known extent of the Khan empire, but exhibit the haplotype in question. As it turns out, folks in that population have an oral tradition that claims they are male-line descendants of Genghis Khan and it had been used to compile a genealogy for them. Zerjal et. al. don’t address how they got there, but do reference a book that discusses the genealogy (all together: <3 citations!)

But the thing that bugging me is tying a haplotype to a single individual. Zerjal et. al. do a good job of making their case, but it’s still a guess (albeit a pretty decent one in my opinion). So, what kind of expectation does it send out to the general public when you tie a single ancestor to a genetic test? I believe it gives people a false sense that there can be that kind of connection on a larger scale and companies are running the risk that people will come into genetic testing expecting to be handed a pedigree chart in exchange for a DNA sample. Perhaps far in the future, as more people are tested, that might be the case. But for now, the reality is that genetic testing might narrow down an area a single ancestor might be from. But that’s ONE ancestor-male or female- and there’s a whole lot more in between that have contributed a lot into making you, and your family, who you are today. And that’s where the real fun, and stories, lie.

However, if you have a serious predilection for little fur hats, we might need to talk…

Y-Chromosome map shown above reposted from Universe-Review.ca[4] who attribute it to Ms. Jane Gitshier of the University of California, San Francisco, published in the August 1993 issue of Science.

[2] http://www.brainyquote.com/quotes/authors/d/douglas_adams.html

[3] http://www.cell.com/AJHG/retrieve/pii/S0002929707605874

[4] http://universe-review.ca/F11-monocell.htm

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