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Blue Eyes

I've been fascinated to read of the latest research on the origins of blue eyes, carried out by Dr Hans Eiberg of Copenhagen. It seems that all people with blue eyes (including me, my parents, and my children; but not my wife, whose eyes are green) share a single identifiable mutation, descended from a single ancestor (or, as one Australian headline sensitively puts it, "Blue-eyed people 'inbred mutants'"; compare Der Spiegel's "All blue-eyed people related to Brad Pitt"). The original mutation likely occurred in near the Black Sea 8-10,000 years ago. Since it's a recessive gene, the first blue-eyed people would not have been born until several generations after the original mutation, as his or her descendants began to intermarry.
The intriguing thing is why we blue-eyed folks became so prevalent in the northern European population - see this map of distribution of "light eyes", taken from a 1960s textbook.
(various internet sources, but originally from from Beals et al., An Introduction to Anthropology, 1965)
There's an assumption underlying a lot of the press coverage (also mentioned by Razib Khan in his blog here) that there was strong positive selection for blue eyes in the northern European population at some point shortly after the mutation happened. There is a linkage between blue eyes, blond hair and fair skin, which is supposedly of adaptive advantage in chilly northern latitudes; there also seems to be some kind of link with adult lactose tolerance.  I am struck by the way in which several media sources mention the role of sexual selection, mainly relying on quotes from other geneticists not themselves involved with the Danish research: see here or here. Surely both men and women play a role in this? It seems rather odd to say that blue eyes have persisted and spread because only one gender finds them attractive! (The media reports seem unable to agree as to whether the blue-eye-fancying gender are babes or dudes.)
Razib also rightly excoriates the "discovery" that all blue-eyed people are descended from the person with the original mutation. In fact, if that person lived as long ago as 10,000 years before the present, it's very likely that all human beings alive today are descended from him or her one way or another; as I've written before, I'm convinced by the calculations that the most recent common ancestor of all humanity lived in historical times, and the original blue-eyed recessive lived much longer ago.

It's easy (and it's also fun) to mock the press coverage for attempting to sex up the Copenhagen research. All rather fascinating, though, and yet another reminder of how closely inter-related we all are.



( 10 comments — Leave a comment )
Feb. 4th, 2008 06:18 pm (UTC)
Hey, we're family! Although, does it count for grey-blue too?

Edit: your first link does not work, it tells me google found nothing for the search, somehow it took me to google belgium in Dutch though. (which is probably the cause for the link not working, but it might be the case for other people where it takes them to the link of their preferred google).

Sorry for the two edits ;)

Edited at 2008-02-04 06:20 pm (UTC)
Feb. 4th, 2008 06:20 pm (UTC)
We're all mutants related to Brad Pitt! It's a total win!
Feb. 4th, 2008 06:28 pm (UTC)
That's very similar to the distribution map for blond(e)s which supposedly 'proves' a single ancestor in modern-day Finland. And yes, so true that we are all descended from everyone.
Feb. 4th, 2008 07:19 pm (UTC)
Makes sense. A similar thing has happened in consumer electronics: the newer blue LEDs are all the rage, outcompeting equally good products with boring old LED colours.
Feb. 4th, 2008 07:25 pm (UTC)
Sexed Up Research
Well, I think I'll defer to the Torchwood model to explain sexual selection. Long winters? I wager that totally-not-like-anyone-I've-ever-met mutant starts looking attractive, no matter the gender/sex of the interested party.
Feb. 4th, 2008 08:00 pm (UTC)
I've written before, I'm convinced by the calculations that the most recent common ancestor of all humanity lived in historical times,

When have you written this? Or, more to the point, where can I find it? I'm very interested in your argument, because intuitively it seems to me unlikely: based on what I've seen, the aborigine population in Australia split off from other human populations about 40,000 years ago, and native populations in North America did the same around 10,000 years ago (or more), both well outside the historical period (unless you think that both groups have so interbred with other human populations that no purely native populations remain--I see that as possible but haven't seen the data to indicate it).
Feb. 4th, 2008 09:44 pm (UTC)
Wikipedia does a fair job of this. Essentially, it only takes one traveller to extend the reach of a common ancestor. You don't need "so interbred", you only need one. The models are interesting.
Feb. 5th, 2008 09:05 am (UTC)
I wrote about this here, with a follow-up here. The aboriginal Australian and North American populations were never completely isolated from the rest of the world, and certainly have not been completely isolated in the last 200 and 500 years respectively since European settlement began. We're all pretty mixed-up!
Feb. 4th, 2008 09:47 pm (UTC)
Actually, you can't rule out your wife. At least three genes are responsible for her or anyone's eye color, and she almost has to be carrying the very same blue recessive gene vaunted in this study in order for you two to have created blue-eyed children. Apparently someone took a scientific finding (a mutation) and overpopularized it to the point where it is nonsensical. I have almost black-hair and brown/green eyes and produced a blue-eyed blonde girl and couldn't have if I hadn't had recessive gene(s) for light colored hair and light colored eyes--the latter inherited from this mutant posthumously enjoying 15 minutes of fame.
Feb. 6th, 2008 12:34 am (UTC)
Puts paid to the theory of a friend of mine that I can't possibly really be Jewish because of my blue eyes...
( 10 comments — Leave a comment )

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