May 10, 2011

Old Blue Eyes

From FOXNews:
Scientist: All Blue-Eyed People Are Related  
"If you've got blue eyes, shake the hand of the nearest person who shares your azure irises: He or she may be a distant cousin. 
Danish researchers have concluded that all blue-eyed people share a common ancestor, presumably someone who lived 6,000 to 10,000 years ago. 
'Originally, we all had brown eyes,' Professor Hans Eiberg of the University of Copenhagen said in a press release. 'But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a 'switch,' which literally 'turned off' the ability to produce brown eyes.'"

Me, Peter Brimelow, Norman Podhoretz, Mrs. Paul Krugman, and Jorge Ramos of Univision should schedule a family reunion!

86 comments:

Blue eyed person said...

Since blue eyes are recessive, this common ancestor himself would have had brown eyes. It's only his grandchildren who cousin-married each other that would have had the first blue-eyed babies, so he probably never even lived to see a blue eye.

What about green and hazel eyed people? Are they related to ol' brown-eyed blue eyes or is that a separate mutation?

Anonymous said...

It's funny how nobody has a good explanation for why blue eyes evolved.

It's also weird how both red hair and blond hair both evolved in Europe, yet the two don't seem to be connected. Is there some natural selection pressure present in Europe but not the rest of the planet that selects for colored eyes and hair? What could it be? Some kind of social or sexual factor?

RKU said...

I actually thought some genetic researchers had already reported that same result a couple of years ago.

And anyway, the whole thing seems pretty obvious on prima facie grounds. Based on Mendelian inheritance, blue eyes are basically controlled by a single gene switch. Since blue eyes are pretty much found only in Northern European peoples, they're clearly due to some sort of relatively recent mutation, and probably didn't exist in the ancestral past.

Now the mutation might have occurred on several different occasions, but it would be a real coincidence if all those occasions happened in exactly the same general geographical area. So the most likely scenario would be a single one-time mutation at some point in the past. Therefore, everyone with blue eyes traces back to that single ancestor.

Anonymous said...

And anyone with an ancestor who has blue eyes would also be a member of the club.

jody said...

i'm not sure this is accurate. there are occassionally people who are not european at all who have irises which are not a shade of brown. i do agree that it is a mutation which turns off the feature, but it can appear in other populations from time to time who don't have any contact with europeans.

this is similar to how hair works if i understand it correctly, where there is no such thing passing on yellow or red hair - what is passed on is a mutation that disables the pigmentation process. all human hair is yellow or red if not instructed to pigment.

i'm hypothesized here before that europeans are what all humans would look like if you disabled or turned off all their feature related genes, leading to that pink flesh phenotype - which many other animals have, like pigs and dogs. that's probably what europeans are. mutants with most of their feature related genotype set to "off".

agnostic said...

Don't forget to invite Paulina Porizkova.

Anonymous said...

interesting! how about max scherzer a baseball pitcher formally with the AZ Diamondbacks but now with Detroit who has one brown eye and one blue eye!!

Anonymous said...

What about use green-eyed devils?

Anonymous said...

do contacts count?

sabril said...

"What could it be? Some kind of social or sexual factor?"

There was an article a few years back which had some interesting thoughts on the subject. Basically, the idea is that European girls were selected for physical attractiveness since they needed commitment from a man in order to have the best chance of reproductive success.

Under such circumstances, it's an advantage for a girl to have different coloring from other girls since she will stand out. So the upshot (according to the article) was for selection pressure towards variety in appearance.

Another interesting thing (which was not discussed in the article) is that arguably in societies where girls feed their own families, one would expect (1) less selection pressure for girls to be sexually attractive, since there's not much advantage in getting a man to commit; and (2) less pickiness among men since they will not have to actually commit to anyone.

Which is exactly what you see in black people. i.e. the girls are very unattractive sexually and the men are not very picky.

Of course, as far as variation in eye and hair color goes, one can ask why it evolved in whites but not orientals. This would seem to undermine the article's hypothesis.

Sheila said...

I know I read recently (perhaps here?) that the number of blue-eyed people is decreasing dramatically. Someone cited a surprisingly high percentage of people in the U.S. as having blue eyes back in the early 1900s. What is the percentage today, in the U.S. and the world? What percent have green eyes? Grey eyes?

I know nothing more than middle school biology, but seem to recall that what I've seen in reality (a full Chinese and a Scandinavian having a blue-eyed blonde child with epicanthic fold eyes) should not occur, given recessive/dominant and all the rest. Can anyone explain this for me in layman's terms?

Anonymous said...

Orientals look very young, though, don't they? Maybe they are selected to look youthful rather than stand out.

Most Orientals have darker skin anyway. And there is such a thing as chance.

SGOTI said...

Damned hazel eyes. I'm some sort of mutt.

Anonymous said...

I thought that blue eyes were well understood. The theory that I had heard was that blue eyes were related to white skin in that both are caused by lack of melanin. White skin is favored by darkish foggy northern places because of Vitamin D and rickets.

Optically blue eyes are generally inferior to brown eyes. The de-pigmented irises allow light to penetrate blurring the vision. All cameras have opaque irises. I did read once however that blue eyes are supposed to see better in the fog - probably a fable.

BTW Vitamin D is now more popular than ever. Pauling was wrong about Vitamin C and everyone was wrong about Vitamin E. Everyone in America especially Blacks are now supposed to take very large Vitamin D supplements. After falling down the mountain last year the orthopedist looked at the X-rays of my back and put me on 2000 units a day.

You wouldn't think that pasty white blue eyed guys like me would need Vitamin D supplements - but that's the current medical opinion. There is support from dermatologists who seem to oppose sunlight under any circumstances.

Albertosaurus

jody said...

"Based on Mendelian inheritance, blue eyes are basically controlled by a single gene switch."

genes don't work that way in the real world. that is an oversimplification used to teach public school students so they can at least get a handle on how biology sort of works. similar to how high school physics class typically reduces the complexity of calculus so the students can at least do some newton style math without having to know differential equations.

real genes are complicated. experts in the field have discovered it's not clear which genes all contribute instructions for brain structure or bone structure. it's not simple and not trivial to make humans smarter or taller by looking at a few genes, it's evident that dozens are involved. apparently even the genes which instruct human eyeballs how to grow are complicated, including how the coloring works. i read some research only a few years ago about how biologists now understand that iris coloration is similar to brain growth and bone growth as far as complication goes.

"how about max scherzer a baseball pitcher formally with the AZ Diamondbacks but now with Detroit who has one brown eye and one blue eye"

this is called dichromatic eyes and also occurs in other animals. again, we can see that any human can end up with the signal to alter or disable pigment production in the iris. all it takes is an error in gene expression.

perhaps some other posters saw the half blue, half red lobster which was pulled out of the atlantic ocean a few years ago. that was exceptionally weird, but all-blue lobsters are pulled out of the ocean from time to time.

pigs are pretty close to humans in many ways as far as tissue goes, maybe they would be a good group to study here instead of the standard rats and monkeys, for a generation-by-generation experiment on heredity. i knew a heart surgeon who told me that they are experimenting with using pig hearts in humans because they are similar, although in a few years, that regeneration lab in north carolina will probably make those experiments moot.

SFG said...

The mutation evolved to allow politically correct teachers in Iowa to make lesson plans:

http://www.pbs.org/wgbh/pages/frontline/shows/divided/

Seriously, it's probably that there's an absence of selective pressure against pigment-defective mutations in Europe, 'cause Europe is cold.

Wes 34th Degree Mason said...

Yes what about green eyed people? Mine are green but my brothers are blue.

Anonymous said...

Certain dogs also have blue eyes.

Clue?

Anon.

RandyB said...

Forget Amren, Vdare, etc.

Let's just organize a family reunion of all blue-eyed people and their blood relatives, and call it a Pride Day! No one can object to that.

Anonymous said...

Since blue eyes are recessive, this common ancestor himself would have had brown eyes. It's only his grandchildren who cousin-married each other that would have had the first blue-eyed babies, so he probably never even lived to see a blue eye.

They were lucky if they weren't diagnosed as witches or warlocks and then murdered by the local [pre-] druidic priests.

Or maybe the priests hailed them as demi-god-like creatures [sprites or pixies or faeries or some such].

tommy said...

It's also weird how both red hair and blond hair both evolved in Europe, yet the two don't seem to be connected. Is there some natural selection pressure present in Europe but not the rest of the planet that selects for colored eyes and hair? What could it be? Some kind of social or sexual factor?

Relaxation of pressure is just as likely. Steve had an article a few years ago about the correlation between cold and foggy climates and blond hair if I recall correctly.

Anonymous said...

So I'm a cousin humping rube.

gcochran said...

Since the eye color trait is largely recessive, the odds are that the selection that drove this allele to high frequency was not on eye color, but some other dominant trait caused by this allele.

It's almost impossible for selection to rapidly increase the frequency of a pure recessive.

corvinus said...

Another interesting thing (which was not discussed in the article) is that arguably in societies where girls feed their own families, one would expect (1) less selection pressure for girls to be sexually attractive, since there's not much advantage in getting a man to commit; and (2) less pickiness among men since they will not have to actually commit to anyone.

Which is exactly what you see in black people. i.e. the girls are very unattractive sexually and the men are not very picky.


Sort of... the impression I get is that European women try to hook men with their beauty, while African women use a kind of raw sexuality to get men to have sex with them but don't really care if they're married or not. In other words, a neutral man would have an African woman for a good time but marry a European woman.

Of course, as far as variation in eye and hair color goes, one can ask why it evolved in whites but not orientals. This would seem to undermine the article's hypothesis.

If the mutation arose on the steppes of Eastern Europe, it would explain it. East Asians are far less genetically diverse than Europeans anyway. Why do you think Koreans all look like they're related to each other?

Wes 35th Degree Mason said...

Since the eye color trait is largely recessive, the odds are that the selection that drove this allele to high frequency was not on eye color, but some other dominant trait caused by this allele.

It's almost impossible for selection to rapidly increase the frequency of a pure recessive.


So is there any idea what other trait is connected with it?

Anonymous said...

"... I've seen Chinese and a Scandinavian having a blue-eyed blonde child with epicanthic fold eyes)...Can anyone explain this for me in layman's terms?"

Simple. The Chinese girl had a recessive gene for blue eyes. I can think of 3 possible sources for it.

(1) Thousands of years ago, blue eyed Tocharians reached Western China.

(2) Western Mongols often have light hair & eyes due to white admixture (Genghis Khan was a redhead!), and the Mongols conquered China at some point.

(3) Finally, there were a lot of British soldiers stationed in China for a while.

So the blue eye gene could have come from several sources. Even weirder, a friend of mine had a cousin, half Japanese/half Chinese, that came out blue eyed also. (Some of the ancient Ainu of Japan may have been blue eyed, or we can perhaps invoke American soldiers in the late 1940s?)

Anonymous said...

"Is there some natural selection pressure present in Europe but not the rest of the planet that selects for colored eyes and hair? What could it be? Some kind of social or sexual factor?"

Monogamy?

Anonymous said...

"So is there any idea what other trait is connected with it?"

Are blues better shots? Were wartime snipers blue eyed?

BD said...

" East Asians are far less genetically diverse than Europeans anyway. Why do you think Koreans all look like they're related to each other?"

Actually, this is not true if you read Cavalli-Sforza.
Even South & North Chinese are quite different with a cline ranging from Mongol to Southeast Asian. The Fst distance is actually closer between English and Punjabis than between North and South Chinese.

"Thank-you" written by Michelle Obama said...

I am curious about Black people with blue eyes.

Since blue eyes are so recessive, how many generations of blue eyed people does it take to take what was a dark-skinned Black person and make his or her ancestors have blue eyes? In other words, how many blue-eyed White people have to be absorbed, on average, in order to make a Black person's lineage have Blue eyes?

Anonymous said...

"So is there any idea what other trait is connected with it?"

The adjective "blue-eyed" also means "naive" in Swedish, Danish, Norwegian, Dutch, German, Icelandic and Finnish.

sky king said...

I read that pilots, especially most of the most famous from WWII, were almost all blue-eyed. Obviously brown-eyed people fly planes, but in any population where there is variation of eye-color, lighter eyes predominate among persons who end up flying planes. Blue eyes do sort of go with the sky.

Polistra said...

How does the appropriately named Eiberg know the mutation happened only once? Has he traced all the other DNA and RNA?

lesley said...

why would anyone think blue eyes could only come from Europe? There are a number of other populations that have been blue eyed for many centuries (I emphasize that because some seeing the pictures might think rampaging soldiers are responsible.) This video shows some "Aryans" (not my word) in Afghanistan, where live some of the whitest looking people outside of Europe. I sometimes wonder why people are surprised at this. Anyone reading about the British in India would have come across accounts of their dealings with the tall, light-eyed mountain men of the Northwest Frontier. Nowadays they make up a fairly large share of the Taliban.

http://www.youtube.com/watch?v=o0TQ1gj8GQo

Anonymous said...

If you go back "6,000 to 10,000 years," just about everybody is related to just about everybody else! Maybe pure blooded American Indians or Australian Aborigines are left out of the fun, but for the rest of us, over a time period like that, it's pretty much guaranteed that there will be multiple connections.

Also:

European hair and eye color
A case of frequency-dependent sexual selection?

Anonymous said...

Those blue-eyed folks in Afghanistan are blue-eyed because the population has distant European ancestry. Just as there are plenty of blue-eyed people in Southern Europe nowadays, but the mutation originated in Northern Europe and spread out from there. The further from Northern Europe you go, the less blue eyes you'll find.

Anonymous said...

How come it's always blue eyes and blue hair being researched? What about red hair? Green eyes?

Peter Frost said...

"Since the eye color trait is largely recessive,"

No, it's not a simple recessive/dominant trait. In any case, even purely recessive traits are sensitive to selection pressures if they're strong enough and if the population is small enough.

"Of course, as far as variation in eye and hair color goes, one can ask why it evolved in whites but not orientals. This would seem to undermine the article's hypothesis."

My argument was that female-female competition for male mates increased along a south-north cline, reaching a maximum in Arctic steppe-tundra. This was due to two factors: (1) lower rates of polygyny because males had to bear the costs of provisioning their female mates and their children during winter (when women are less able to provide for themselves); and (2) higher rates of male mortality because of longer hunting distances with fewer alternate food sources.

Potential male mates were least available in Arctic steppe-tundra. In such environments, women had few opportunities for food gathering and largely depended on men for food provisioning. At the same time, hunting distances were at a maximum because the main food sources were highly mobile herds of herbivores (e.g., reindeer).

Steppe-tundra used to stretch across all of northern Eurasia. In northern Asia, however, it ran farther north and was farther removed from the moderating influences of the Atlantic Ocean and the Gulf Stream. Human occupation of this portion of the Eurasian steppe-tundra does not seem to have been continuous, particularly at the height of the last ice age (15,000 to 20,000 years ago). Thus, the cumulative effects of sexual selection were strongest in the European portion, where human occupation was more continuous.

For more information, please consult my article "Sexual Selection and Human Geographic Variation"
http://137.140.1.71/jsec/articles/volume2/issue4/NEEPSfrost.pdf

Wes 36th Degree Mason said...

Anyone reading about the British in India would have come across accounts of their dealings with the tall, light-eyed mountain men of the Northwest Frontier. Nowadays they make up a fairly large share of the Taliban.

Well no wonder no one can beat them ... they are Aryans!

Difference Maker said...

it can appear in other populations from time to time who don't have any contact with europeans.

Such as..?

Difference Maker said...

There was an article a few years back which had some interesting thoughts on the subject. Basically, the idea is that European girls were selected for physical attractiveness since they needed commitment from a man in order to have the best chance of reproductive success.

I find the theory described in the article plausible. Such ideas were articulated by the 19th century already as well.


Of course, as far as variation in eye and hair color goes, one can ask why it evolved in whites but not orientals. This would seem to undermine the article's hypothesis.

It was the environment, lolololol

Difference Maker said...

BTW Vitamin D is now more popular than ever. Pauling was wrong about Vitamin C and everyone was wrong about Vitamin E. Everyone in America especially Blacks are now supposed to take very large Vitamin D supplements. After falling down the mountain last year the orthopedist looked at the X-rays of my back and put me on 2000 units a day.

You wouldn't think that pasty white blue eyed guys like me would need Vitamin D supplements - but that's the current medical opinion. There is support from dermatologists who seem to oppose sunlight under any circumstances.


Vitamin D overdose may cause premature aging. Folks, hold off on megadosing.

I wonder if there's a nefarious conspiracy involved here.

Svigor said...

Anon, I've heard "cuckold detector" and sexual selection as explanations for blue eyes.

Svigor said...

interesting! how about max scherzer a baseball pitcher formally with the AZ Diamondbacks but now with Detroit who has one brown eye and one blue eye!!

Kate Bosworth has something like that, except one eye is mostly blue and only partially brown. I don't know if it's genetic or what.

Is this the chimera thing?

Difference Maker said...

Simple. The Chinese girl had a recessive gene for blue eyes. I can think of 3 possible sources for it.

In my case it will be a Scandinavian girl.

There used to be large expat Persian communities in the southeast of China until they rioted or raised armies and perished in the wars, and the Dutch maintained a colony on Taiwan whose members were apparently not all deported.

Relaxation of pressure is just as likely. Steve had an article a few years ago about the correlation between cold and foggy climates and blond hair if I recall correctly.

Obviously, the environment matters in precluding / selecting for certain traits.

why would anyone think blue eyes could only come from Europe?

Those Afghanis originate from Europe. "Europeans" originated as horse and cattle breeders on the Pontic Caspian steppes. Interestingly, the original Persians or Aryans probably really were blond.

Svigor said...

Under such circumstances, it's an advantage for a girl to have different coloring from other girls since she will stand out. So the upshot (according to the article) was for selection pressure towards variety in appearance.

Could just be that neoteny is, ceteris paribus, attractive in women.

Svigor said...

Are blues better shots? Were wartime snipers blue eyed?

Some time back a commenter here asserted that some ridiculously high percentage of winning Superbowl quarterbacks were blue-eyed. If that's true, I bet you see the same thing in fighter jocks and race car drivers.

Anonymous said...

If the mutation arose on the steppes of Eastern Europe, it would explain it. East Asians are far less genetically diverse than Europeans anyway. Why do you think Koreans all look like they're related to each other?

Yes, but Northern Europeans are far less genetically diverse relative to Africans.

gcochran said...

"The Fst distance is actually closer between English and Punjabis than between North and South Chinese."


Not so.


If the genes are identical for an extended region around the mutation, you can be pretty sure that the mutation happened once.

Relaxed selection almost automatically turns into redirected selection. Most genes are pleiotropic, do several things, wear more than one hat. This interferes with optimization of any one function - any change has to preserve the other functions as well. But if one of the functions becomes essentially irrelevant (like darkening skin), selection could favor changes that interfere with melanization but improve some other function. If interfering with the melanization actually has a positive benefit, possible when considering vitamin D, you should see remarkably rapid evolution in genes in the melanization pathway.
Which we do.

Anonymous said...

i'm hypothesized here before that europeans are what all humans would look like if you disabled or turned off all their feature related genes

This is quite funny.

Kristen said...

My kitten's breeder told me that blue-eyed cats have white or light fur and dark-eyed cats have darker fur. True? If so, there may be something to the notion that recessive eyes and skin are part of an overall diminution or repression of melanin.

Still, I'd be a bit surprised if the mutation that occurred in humans also occurred in dogs, cats, etc. Low odds. More likely, some sort of evolutionary or biological advantage occurs in all low-melanin creatures, though I don't know what it is.

Kristen said...

gcochran -- after reading your post I want to ask you this: Why don’t pleiotropic genes optimize intelligence, which is obviously an important and needed function in contemporary society? I don’t see any remarkably rapid evolution in intelligence, or is there? Wouldn’t raw intelligence be one of the most important functions of genes, more so than blue eyes, skin color or other less crucial functions?

Anonymous said...

"why would anyone think blue eyes could only come from Europe?"

I think the idea is they developed in Europe and then spread with the Indo-Europeans (Aryans).

http://en.wikipedia.org/wiki/Proto-Indo-Europeans

Anonymous said...

One thought i had on the sexual selection angle was if a culture has a surplus then a dowry system would compete with looks but what if you were on the edge of subsistence?

http://en.wikipedia.org/wiki/Economy_of_the_Cucuteni%E2%80%93Trypillian_culture

I'd imagine both looks and pair-bonding might come to predominate.

Anonymous said...

"I don’t see any remarkably rapid evolution in intelligence, or is there? Wouldn’t raw intelligence be one of the most important functions of genes"

The question wasn't directed at me but i'm not at all convinced that extremely high IQ has less disbenefits than extremely low IQ, in which case the selection pressures would cause the mid-point of the bell curve to drift towards the optimum point and then wobble around it.

Ortu Kan said...

Some of the ancient Ainu of Japan may have been blue eyed

This gets thrown out quite a bit on the Internet, but I've never seen it credibly backed up. Photos are certainly wanting (in contrast to blue eyes from the Indian subcontinent or Mongolia, for instance), and I know of it neither from any wajin Japanese depictions either of Ainu or emishi nor from first-hand Western accounts. Sometimes the claim is attributed to Kodama, but he says nothing of the sort, at least in his 1970 English-language book.

Probably the Ainu eye is more frequently light brown or hazel than that of non-Ainu Japanese, occasionally inclining to grayish.

RKU said...

Kristen: Wouldn’t raw intelligence be one of the most important functions of genes, more so than blue eyes, skin color or other less crucial functions?

Actually, it's pretty clear that raw intelligence really isn't all that important, at least compared with lots of other traits.

IQ is normally distributed, and as might be expected, this means it's governed by a very large number of genes of very small effect. If intelligence had been subject to strong selective pressure for the last few hundred generations, the smarter alleles would have mostly fixated and the dumber alleles would have mostly disappeared, and the distribution would no longer be so strongly Gaussian. Therefore, although intelligence may have had some survival value---more in some places and less in others---the value wasn't enough to overwhelm other pressures and de-normalize the distribution, although there certainly may have been some sweeps by individual intelligence genes.

It's the same with height, which is also Gaussian and apparently caused by lots of small genes. Getting either very much taller or very much shorter probably hasn't been beneficial.

read it said...

"It's funny how nobody has a good explanation for why blue eyes evolved."


It's funny how so many have no idea how evolution works.


The article clearly stated it was a random mutation. The person who had it passed it to his/her offspring. They passed it on, etc. It wasn't a lethal mutation and as chance would have it, it just kept getting passed on. That is it.

Wes is controlling your batch process said...

"read it", I think everyone has a clue how evolution works here, it's just trying to understand if there was some benefit associated with the mutation that led to blue eyes becoming prevalent in some populations.

gcochran said...

Peter: First, an advantageous allele whose action is purely recessive is far more likely to be lost when new than a dominant allele with an equivalent advantage. Second, assuming that it is not lost and that the population mates randomly, it takes much longer to reach 50% frequency than a dominant allele. Third, if the population is spread out over space, the Fisher wave spreads far more slowly, something like 20 times more slowly.

Anonymous said...

"It's also weird how both red hair and blond hair both evolved in Europe"

The gene for red hair pre-dates the exodus from Africa. Selection, drift, and/or founder effect accounts for the higher occurence of red hair in Europe.

For the same reason, the gene for blue eyes did not necessarily originate in Northern Europe, or even in Europe at all.

The genetics of eye color are actually quite complicated.

"The mutation evolved to allow politically correct teachers in Iowa to make lesson plans."

Politically correct? More like insane.

Anonymous said...

"The article clearly stated it was a random mutation. The person who had it passed it to his/her offspring. They passed it on, etc. It wasn't a lethal mutation and as chance would have it, it just kept getting passed on."

"Getting passed on" doesn't explain its increase in frequency. The individual who developed this mutation, say 10,000 years ago, was far from the only person alive in Europe (or wherever). Yet at least one copy of his allele is now carried by a considerable fraction of Europe's population.

Anonymous said...

Me, Peter Brimelow, Norman Podhoretz, Mrs. Paul Krugman, and Jorge Ramos of Univision should schedule a family reunion!

So much for the notion that Jews kept their bloodlines intact and unsullied since the dawn of time then.

Nostradamus said...

Blue eyed people are partially descended from space aliens who landed near Ur of the Chaldees in 4004 B.C. And persons with green eyes, of course, are partially descended from the Lizard People who secretly control the world.

Wes of the Lizard People said...

OMG Nostradamus I have my eye on you. This information was not to be disclosed to the public until 2012.

josh said...

Isn't this kind of obvious. I mean, how *else* could the blue eyed gene have been spread?

Anonymous said...

My people, my people!!!

rec1man said...

The kalash people in North west Pakistan have blue eyes

Genetically they are quite distinct from Europeans

rec1man said...

The kalash people in North west Pakistan have blue eyes

Genetically they are quite distinct from Europeans

Peter Frost said...

"Peter: First, an advantageous allele whose action is purely recessive is far more likely to be lost when new than a dominant allele with an equivalent advantage."

Greg: Eye color does not follow a simple blue/brown recessive/dominant pattern of inheritance. Heterozygotes can exhibit a range of non-brown phenotypes, notably green eyes.

Simple English: selection for novel eye colors will not be drowned out in the next generation by a sea of brown eyes. You may not have blue eyes, but you'll have lots of green ones.

But let's assume that there are only two eye colors: blue(recessive) and brown (dominant). That isn't at all the case, but let me enter your evolutionary scenario. If there is repeated sexual selection for blue eyes, the load of recessive alleles will gradually build up in the population, and the probability of these alleles being expressed as homozygotes will increase proportionately.

These recessive alleles are not "lost." They're still there.

Svigor said...

So much for the notion that Jews kept their bloodlines intact and unsullied since the dawn of time then.

Does that myth even pass the seriousness test for mentioning here? It's pretty obvious Jewry has been open to small amounts of new blood for thousands of years. One-way gene flow is a fair description, though; there's been a LOT more Jewish blood entering the non-Jewish population over time. That's part of why I scoff at the "the Jews are disappearing" thing; they've been "disappearing" for 3,000 years. This is all part and parcel of their "elite head without a body" strategy.

Ted Plank said...

Re: Sky King, I read somewhere that one of the common links of the Luftwaffe fighter pilots who shot down over 100 planes (roughly a hundred shot down over 100, several shot down over 200 and 2, Gerd Barkhorn [301] Erich Hartmann [352] shot down over 300) was that they had a much higher presence of blue eyes. I tried to find a reputable link for this, but no dice.

Another item of note was that most of them sired daughters.

covered by all insurances said...

Vitamin D isn't doing anything for
Albertosaurus' facility with English:

After falling down the mountain last year the orthopedist ...

Anonymous said...

"And persons with green eyes, of course, are partially descended from the Lizard People who secretly control the world."


Now I finally know why I am such a control freak.

It is the green eyes.

Anonymous said...

Vitamin D overdose may cause premature aging. Folks, hold off on megadosing.

I presume that the wise readers of this blog won't blindly accept medical advice from a random commenter. Ask your doctor. Get tested.

In fact I argued with the orthopedist and my GP both of whom wanted me to take a lot of Vitamin D.

I'm very fair and I get outside everyday. The San Francisco Bay Area has a lot of sunshine. The idea that I would be a candidate for osteoporosis seemed crazy.

Furthermore I haven't shrunk. In the last fifty years I have only lost one quarter inch from my peak height. My dentist tells me that he lost two full inches the previous year. He's the one, I thought, who needs supplements not me.

But then I read "The Vitamin D Solution" by Hollick. He argues for big supplements. BTW I never ran across any indication that Vitamin D promotes premature aging.

Make up your own mind.

Back on topic:
As I understand it the protein in the iris is bluish colored. Eyes are brown only because of melanin. That pigment makes them more efficient optically because it creates a sharper and better defined aperture.

There has been selective pressure on northern populations to reduce melanin so as to avoid rickets. White skin produces more Vitamin D. Blue eyes were not selected for independently but just arose from other melanin reduction selective pressures.

So Cochran's objection of a recessive advancing in frequency too fast is not relevant nor is the idea of sexual selection. Blue eyes come from white skin which comes from the need for Vitamin D.

I might be wrong.

Albertosaurus

David Gress said...

Muy interesante, Steve.

My wife, a blue-eyed Dane, tells me that her mother, also blue-eyed, always told her not to trust brown-eyed people, because they were treacherous. Unfortunately I am brown-eyed, inherited from my father. So she always has this rhetorical weapon ...

So now I can tell her that she is the biological freak.

We'll laugh about this.

Anonymous said...

I'm amazed that no-one here points to this chain of logic:

[1] If the gene for blue eyes developed 6-10k years ago, and now roughly half of the Europeans are blue eyed, it MUST have enjoyed benefits of selection.

[2] The selection MUST be due to sexual selection since blue eyes have no survival advantage.

[3] If sexual selection was present over such a long time, it will probably remain in place in the future.

[4] In the long run, the gene will keep spreading to other populations, and may eventually even become the most common eye color (See how popular colors are in animal kingdom).

[5] The global spread of the genes for the spread of blue eyes requires mixing of whites with other populations.

[6] Mixing of whites and others will cause a temporary reduction in the share of phenotypic blue eyes due to its recessiveness.

ben tillman said...

Some time back a commenter here asserted that some ridiculously high percentage of winning Superbowl quarterbacks were blue-eyed.

Hi!

ben tillman said...

See here:

http://isteve.blogspot.com/2009/10/rush-limbaugh-and-black-quarterbacks.html

Black vs. white QBs in the NFL? What about eye color? At last check I think blue-eyed QBs still constituted about 80% of the winners. Bradshaw (4), Montana (4), Aikman (3), Brady (3), Starr (2), Namath (1), Dawson (1), Unitas (1), Staubach (2), Elway (2), Young (1), Griese (2), Stabler (1), Theismann (1), Simms (1), Hostetler (1), etc.

That was two years ago.

Since then, we've had Brees (hazel?) and Rodgers (blue).

ben tillman said...

The selection MUST be due to sexual selection since blue eyes have no survival advantage.

You don't know this!

Difference Maker said...

I'm amazed that no-one here points to this chain of logic:

1. There is a whole suite of features that are sexually selected, and blue eyes appear to have some other mysterious advantages.
2. Would be kind of weird harping on how sexy I find such and such eye color
3. Our evil overlords might get funny ideas.
4. No point if others don't see it already

Difference Maker said...

I might be wrong.

Albertosaurus


You are.

Anonymous said...

I had blue eyes up to age 21. I now have greenish-blue eyes that go back and forth over time. My eye doctor told me I have a genetically recessive gene that causes this. My brother had brown eyes that turned to grey. This is unheard of and super rare. Brown eyes of grown ups do not change color. Call it weird, fate or chance

Peter Frost said...

"Blue eyes come from white skin which comes from the need for Vitamin D."

Albertosaurus,

Among Europeans, the correlation is very weak between skin color and eye color. Two different gene loci are involved. European skin was whitened through allelic change at SLC45A2 (aka as AIM1) European eye color diversified through changes at the OCA2-HERC2 gene complex.

Having a greater diversity of eye colors (and also hair colors, which involve yet another gene) does nothing to improve a population's vitamin-D status.

And yes, too much vitamin D causes premature aging. We know this from work with mice that have been genetically engineered to have higher levels of vitamin D. The range of optimal vitamin-D levels appears to be relatively narrow, so there is a definite risk of overdoing it.

Anonymous said...

Let's get quantitative here. I have been accused of inducing people to overdose on Vitamin D. A couple people have noted that there are some bad consequences from taking too much Vitamin D. True, but how much is too much?

Most multivitamin tablets contain 400 units. This level is considered too low by many medical people including my own doctor. I take 2000 units a day. I take a 1000 unit pill twice a day. I also take fish oil and a commercial multivitamin.

The Wikipedia article on Hypervitaminosis D states that toxicity comes from taking 600,000 to 1,600,000 units a day for several months.

If I were to take six to sixteen full bottles a day I would be in trouble. Not bloody likely!

As Paracelsus noted a while back the dosage makes the poison.

Vitamin A is more dangerous especially if you eat polar bear liver. But I suppose Global Warming is solving that problem. LOL.

My multi vitamin pill has 3500 units of Vitamin A. I could over dose on A with only about five pills a day. As noted above I would have to take 600 to 1,600 Vitamin D pills a day to be similarly endangered.

Albertosaurus

Anonymous said...

It has also been stated that eye color is not correlated with skin color as I had assumed. Really?

The original article that is the subject of the blog posting stated: "

...the OCA2 gene, which regulates the pigmentation of our eyes, hair and skin...

The Wikipedia article on eye color states:

OCA2 gene polymorphism, close to proximal 5′ regulatory region, explains most human eye-color variation.

The maps of blue eye prevalence show that it is strongly centered on Scandinavia.

So if I was naïve to assume that White skin correlated with blue eyes, I'm not alone.

A recent Discovery Magazine article stated:

Our results confirmed the association of HERC2 rs12913832 with eye colour and showed that this SNP is also significantly associated with skin and hair colouration.

I'm no expert but I also don't think I've been refuted yet by those here who want to assert that eye color and skin color are completely independent.

Albertosaurus