6 ms·

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have

by BRadmin 17y ago

"Nobody 10,000 years ago had blue eyes," Hawks said. "Why is it that blue-eyed people had a 5% advantage in reproducing compared to non-blue-eyed people? I have no idea." Now that's interesting. Any theories?

baltoo 17y ago
As I've heard it, the development of both blue eyes and blond hair is thought of as mainly being driven by sexual preferences, i.e. status of novelty. Sexual preferences are pretty strong drivers and combined with periods of harsh environments (e.g. where either of the sexes die off early in life) can create really fast evolution.
deleted 17y ago
[deleted]
slackerIII 17y ago
The theory I've heard is that a blue iris makes it easier to see pupil dilation, which is an indication of attraction. People are more likely to hook up when they can tell the other person is attracted to them, so...
- prat 17y ago
  That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.
  - nopassrecover 17y ago
    While it is irrelevant to your point, I'd like to make a note about your example. Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the ability of a tribe to defend itself. If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting.
    - req2 17y ago
      Cancer may simply have been an example of kind, rather than specific to the case at hand; however, I wouldn't disregard it as quickly as you do. The grandmother hypothesis [http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-weapon-grandma/ http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-w...] supports cancer resistance as an evolutionarily beneficial gene. You also miss the obvious unstated point that cancer resistance itself may just be a side effect of another characteristic, such as more efficient mitochondria. Your third paragraph fails to support any of its assertions; cancer resistance takes many forms, and most mutations are negative in nature: some math would likely be necessary to support a (carefully worded) argument in either direction.
    - prat 17y ago
      I agree about the child bearing age point..resistance to infectious disease may have been a better example. but re your last point, being prone to cancer could speed up evolution but at the same time could wipe out a sub population? infact- that (probably) holds for anything that speeds up evolution - but again math models would be needed to prove that.
    - JMostert 17y ago
      "If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting." Evolution doesn't work that way. It doesn't favor mutation because mutation is "good" for evolution. You have to look at it from individual genes, and there the story is just the opposite. Evolution happens in spite of, not because of genetic predisposition to mutation, because it's vastly more likely for a mutation to be pointless or harmful than beneficial. If you have a gene that makes mutation in the genepool overall less likely, that gene will be more successful at spreading itself, because the mutants have, on the whole, far less chance of success than the originals (which have already proven their worth in a long chain of ancestor individuals carrying them). Of course every so often a mutant gets lucky and is more successful (or at least not less successful) than the original -- this is what selection is all about -- but statistics are against them. To elaborate your scenario: suppose the environment changed very rapidly, and adaptation in some direction were necessary to survive it. If by some stroke of luck a gene that increased the mutation rate happened to be there at that moment, defying the odds, it would find a favorable environment, but only for as long as the rapid change is required. Generalizing this: a successful genepool is one where the mutation rate is "just right" for adapting to the environment. Too much mutation and the genepool isn't stable and will eliminate itself, too little mutation and the genepool will be eliminated by the environment. In this balance, the odds are stacked in favor of avoiding mutation. And all this is orthogonal to the discussion of how cancer (the uncontrolled reproduction of cells) is related to the capacity for mutations (infidelity in the copying process). Cancer resistance and mutation resistance are related, but by no means the same thing. To borrow a computer image: your computer has copy processes with very high fidelity (only the occasional alpha particle to spoil the fun) but this doesn't protect it against worms, which copy themselves unwantedly but with the same high fidelity. This analogy is badly flawed in obvious ways (regular programs are not designed to copy themselves, cells are), but I hope it gets the point across.
anigbrowl 17y ago
Novelty? I have red hair, which I'm not sure is adaptive (eg it puts me at greater risk for skin cancer) but which partners have rated highly as an attractive feature specifically because it's unusual. Then again I have a compulsive draw towards partners from outside my own ethnic group, so there's some selection bias going on with that interpretation.
- Tichy 17y ago
  I think being attracted to different ethnic groups might have an advantage, too - keeping diversity in the gene pool up is probably beneficial.
  - hughprime 17y ago
    Except that in practice, it hardly ever happened until very recently. Ethnic groups lived far apart, and those folks who lived near a boundary between two different ethnic groups would hardly ever interbreed with the others (whether that's mostly cultural or a lack of attraction, though, I'm not sure). Even now, it happens surprisingly infrequently.
    - foldr 17y ago
      >and those folks who lived near a boundary between two different ethnic groups would hardly ever interbreed with the others If you are talking about prehistory, how can you know this?
      - hughprime 17y ago
        Well, inferring from the observed behaviour of stone-age tribal peoples in historical times.
        foldr 17y ago
        That's a bit vague. Has anyone run the stats on the incidence of cross-tribal sex? And where would they get the data?
breck 17y ago
"Nobody 10,000 years ago had blue eyes," My reaction is that he misspoke here or he overstated his claim to make a point. I know nothing about the proportion of people with blue eyes back then or right now for that matter. But I think at the very least, you could only make that claim with a tiny, tiny, tiny amount of confidence. Maybe the proportion of humans with blue eyes was smaller back then, maybe it was larger, or maybe it was the same. I don't know. But to claim nobody 10,000 years ago had blue eyes is an impossible point to prove unless you have DNA samples from every human alive 10,000 years ago. We might be able to say that all the people alive today with blue eyes descended from one ancestor, but we can't claim to know about the population of people with blue eyes back then. For all I know, half the population 10,000 years ago could have had blue eyes but then got wiped out by swine blue. That's like saying no one 100 years ago was over 7'6" tall. I know a bit more about height and think that this statement may be true. But it would be real hard to prove. Now shift the timespan back by 2 orders of magnitude, and I think it'd be harder to prove. I'm not saying that the general idea is wrong, but I'm just it would be a good idea to question that claim a lot before thinking about reasons why that might be the case.
- aaronblohowiak 17y ago
  " We might be able to say that all the people alive today with blue eyes descended from one ancestor" -- exactly. And, if you follow the science of using mitochondrial DNA to date genetic changes.. http://en.wikipedia.org/wiki/Molecular_clock http://en.wikipedia.org/wiki/Molecular_clock http://www.livescience.com/health/080131-blue-eyes.html http://www.livescience.com/health/080131-blue-eyes.html
- BRadmin 17y ago
  All blue eyed people traced to 10000 year old ancestor: http://www.dailymail.co.uk/sciencetech/article-511473/All-blue-eyed-people-traced-ancestor-lived-10-000-years-ago-near-Black-Sea.html http://www.dailymail.co.uk/sciencetech/article-511473/All-bl...
  - breck 17y ago
    Interesting. Thanks for the link. Although I'm not convinced from the results of one study, now I understand what the genesis of the original comment was. Evolution is a fascinating subject. I think it would be neat if all our schools taught 12 years of Reading, Writing, Arithmetic and Evolution.
tyn 17y ago
You could just attribute it to the attractiveness of blue eyes. Most people consider blue (and green) eyes more beautiful than eyes with a different color. But this will get you only as far as the next inevitable question: why are blue eyes attractive?
- baltoo 17y ago
  Status will always be defined by scarcity. Perhaps blue eyes where novel and scares, which could be enough?
- rsheridan6 17y ago
  Children are have lighter eyes (and everything else) than adults. It's a sign of youth.
  - joubert 17y ago
    Huh? Are you saying Blue is a lighter shade of Brown?
    - mmt 17y ago
      Yes, if by "shade" you mean the color progression that human (and other mammals') eyes make in their development.
      - joubert 17y ago
        But your eyes don't change from blue to brown as they develop, or do they?
        elemenohpee 17y ago
        yep:http://chemistry.about.com/cs/howthingswork/f/eyecolor.htm http://chemistry.about.com/cs/howthingswork/f/eyecolor.htm)
        17y ago
gojomo 17y ago
Speculation in no particular order: (1) Perhaps less pigment in the eyes improves vision in certain conditions (especially those in colder latitudes). (2) As a recessive trait, blue-eyed mating limited a woman's ability to pass off offspring from other (dark-eyed) fathers as that of a blue-eyed father. This greater confidence in paternity won greater fatherly support, and in some eras/places (inheritable property?) this dominates the advantages of promiscuity. (This effect may fade or even reverse depending on proportion of eye colors.) (3) Handicap principle -- even if blue-eyes are a disadvantage in some dimensions (sun-robustness, alien look), sometimes a conspicuous disadvantage is effective as a signal that fitness in other harder-to-measure dimensions is better. ( http://en.wikipedia.org/wiki/Handicap_principle http://en.wikipedia.org/wiki/Handicap_principle ) (4) I suspect just about any unique visible characteristic, advantageous or mildly disadvantageous, can find some reinforcement as a quick signal of genetic kinship against outside competitive groups that look different. So just, "different enough to tell closer-cousins from distant-cousins" could be a sufficient explanation.
tokenadult 17y ago
Beats me. I married someone with brown eyes (and black hair). On the other hand, she married a man with blue eyes (and blond hair), and my genes have been replicated into four children. My dad's genes for red hair have passed on to be expressed in two of my children.
- tamas 17y ago
  Blue eyes and blonde/red hair are recessive traits, while brown eyes and hair are dominant. You having blue eyes means both of the gene pairs that control eye color have the recessive blue, while your wifes brown eyes can be caused by having a set of blue and a set of brown genes, and as brown is the dominant one, it is what was actually expressed in here eye color. The fact that your children have blue eyes means she does have genes for blue eyes, and they are inherited into your children as well as your blue genes, hence their blue eyes. The same goes for blonde/red vs brown hair. Either that, or consult with your milkman/gardener.
  - tokenadult 17y ago
    You having blue eyes means both of the gene pairs that control eye color have the recessive blue, while your wifes brown eyes can be caused by having a set of blue and a set of brown genes, and as brown is the dominant one, it is what was actually expressed in here eye color. My wife is from a part of China that is not very likely to have any genes for blue eyes (or red hair) in the indigenous population. The overwhelming probability is that she is homozygotic for both black hair and brown eyes. The fact that your children have blue eyes means she does have genes for blue eyes There is a reading problem here, because I never said anywhere in my post that any of my children have blue eyes. (In fact, these days I am startled whenever I see a child with blue eyes, even though I grew up with siblings with blue eyes, because all my children and my wife look at me with brown eyes. I see blue eyes and ask myself, "Do they make eyes in that color too?") You also are well advised to do more reading about the genetics of human eye color and hair color http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Human_hair_color http://en.wikipedia.org/wiki/Human_hair_color and human genetics in general. Genes can recombine from one generation to the next. My red-haired dad, by the usual assumption that you made in your reply, was homozygotic for red hair, making me presumptively heterozygotic for red hair, while my wife presumptively is not a carrier of that trait at all, on population genetics probabilities. But two of my children have hair that is "brown" at a glance but also includes red pigment (as can be seen when their hair is backlit by sunlight or when strands of their hair are observed under a microscope). Sometimes children can inherit a double copy on one gene from just one parent, as anyone who has carefully studied human genetics knows. http://www.ncbi.nlm.nih.gov/omim/ http://www.ncbi.nlm.nih.gov/omim/
jordyhoyt 17y ago
How do we know that nobody 10,000 years ago had blue eyes? Er, well, of course it's impossible to _know_, but what leads us to conclude that nobody 10,000 years ago had blue eyes? Anyone know? Edit: posted this before I saw the other thread and the excellent answer here - http://news.ycombinator.com/item?id=824543 http://news.ycombinator.com/item?id=824543 My mistake.
asdlfj2sd33 17y ago
Don't only Caucasians have blue eyes? And aren't they (full disclosure "we" in my case) also the only ones with the mutated version of the gene which controls how much melanin is deposited in skill, hair and... I think also irises? Asians and Africans both have the normal version of the same gene. And melanin has many roles, sun protection being just one, the other is as a structural protein. Just compare how black skin ages vs. how a redhead of the same (advanced) age looks. And why would Caucasians have a mutation which deposits less of such a useful protein? Vitamin D. It is produced when UV light hits the skin. In northern climates with less sun, and skin being covered or you die of exposure, often even when the sun is up, people get a lot less vitamin D. Inuit get more due to their diet, and modern man also gets much more again because of diet. And yet most people living in the north even today lack vitamin D. Also, I thought all of the above is common knowledge which makes me question the whole article.
- aaronblohowiak 17y ago
  "Don't only Caucasians have blue eyes?" No. More than you ever wanted to know about eyes: http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Eye_color Also, this is neat: A 2002 study found the prevalence of blue eye color among Caucasians in the United States to be 33.8 percent for those born from 1936 through 1951 compared with 57.4 percent for those born from 1899 through 1905.[10] Blue eyes have become increasingly rare among American children with only 1 out of every 6 – 16.6 percent which is 49.8 million out of 300 million (22.4% of white Americans) of the total United States population having blue eyes.[33][34] The plunge in the past few decades has taken place at a remarkable rate. A century ago, 80 percent of people married within their ethnic group. Blue eyes, a genetically recessive trait, were routinely passed down, especially among people of Scottish, English, Irish, Welsh, Western and Northern Slavic, and Northern European ancestry.[33][34][35] In the 1930s, eugenicists[citation needed] used the disappearance of blue eyes as a rallying cry to support immigration restrictions. They went so far as to map the parts of the country with the highest and lowest percentage of blue-eyed people.[citation needed]
  - asdlfj2sd33 17y ago
    From your wikipedia link: Blue eyes contain low amounts of melanin... Blue eyes are most common in Northern Europe and Central Europe and to a lesser degree in Southern Europe,North America and southern Central Asia; Afghanistan is a notable example.[30] They're also found in parts of North Africa,[31] West Asia, and South Asia[32], in particular the northern areas of India and Pakistan. It can rarely occur as far south as Sri Lanka. However blue eyes are not found within the population of East Asia, due to the major pre-dominance of the brown eye gene in the area. Central Asians, people from the Caucasus, Afghans, Pakistanis, and even Indians darker then many an African are considered Caucasian. They are Caucasians. And North Africa is full of Caucasians, hell even German tribes, Goths if I recall correctly, settled there during Roman times. So only Caucasians have Blue eyes. Again because of a gene mutation which control how much melanin is deposited in hair, skin, and irises. Someone with a lot of melanin could have blue eyes, but they wouldn't appear blue do the the melanin. That's why blue eyes contain low amounts of melanin. And low amounts of melanin are related to vitamin D, which is related to living in northern climates.
kqr2 17y ago
Does anyone know if blue-eyed people continue to have a 5% advantage?
tome 17y ago
It seems to me that amongst (white) people who play badminton, a larger proportion have blue eyes than amongst the general population. A friend told me that in baseball, batters have a higher tendency towards blue eyes, and pitchers to brown, but I couldn't find any references. Does anyone know if this has any scientific basis?
ryne 17y ago
Is there any credit to the rumour that blue-eyed individuals have better sight, indicating why there are so many blue-eyed fighter pilots etc?

by BRadmin 17y ago

baltoo 17y ago

As I've heard it, the development of both blue eyes and blond hair is thought of as mainly being driven by sexual preferences, i.e. status of novelty. Sexual preferences are pretty strong drivers and combined with periods of harsh environments (e.g. where either of the sexes die off early in life) can create really fast evolution.

deleted 17y ago

[deleted]

slackerIII 17y ago

The theory I've heard is that a blue iris makes it easier to see pupil dilation, which is an indication of attraction. People are more likely to hook up when they can tell the other person is attracted to them, so...

prat 17y ago
That is possible, but the gene for blue eyes may also be linked with some other characteristic (biologically more relevant than attraction - like resistance to cancer) that might provide selective advantage. Linkage (close enough genes travel together) among genes plays a huge role in selection but often, and understandably, we regard the the feature that is easily visible to us as essential.
- nopassrecover 17y ago
  While it is irrelevant to your point, I'd like to make a note about your example. Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the ability of a tribe to defend itself. If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting.
  - req2 17y ago
    Cancer may simply have been an example of kind, rather than specific to the case at hand; however, I wouldn't disregard it as quickly as you do. The grandmother hypothesis [http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-weapon-grandma/ http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-w...] supports cancer resistance as an evolutionarily beneficial gene. You also miss the obvious unstated point that cancer resistance itself may just be a side effect of another characteristic, such as more efficient mitochondria. Your third paragraph fails to support any of its assertions; cancer resistance takes many forms, and most mutations are negative in nature: some math would likely be necessary to support a (carefully worded) argument in either direction.
  - prat 17y ago
    I agree about the child bearing age point..resistance to infectious disease may have been a better example. but re your last point, being prone to cancer could speed up evolution but at the same time could wipe out a sub population? infact- that (probably) holds for anything that speeds up evolution - but again math models would be needed to prove that.
  - JMostert 17y ago
    "If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting." Evolution doesn't work that way. It doesn't favor mutation because mutation is "good" for evolution. You have to look at it from individual genes, and there the story is just the opposite. Evolution happens in spite of, not because of genetic predisposition to mutation, because it's vastly more likely for a mutation to be pointless or harmful than beneficial. If you have a gene that makes mutation in the genepool overall less likely, that gene will be more successful at spreading itself, because the mutants have, on the whole, far less chance of success than the originals (which have already proven their worth in a long chain of ancestor individuals carrying them). Of course every so often a mutant gets lucky and is more successful (or at least not less successful) than the original -- this is what selection is all about -- but statistics are against them. To elaborate your scenario: suppose the environment changed very rapidly, and adaptation in some direction were necessary to survive it. If by some stroke of luck a gene that increased the mutation rate happened to be there at that moment, defying the odds, it would find a favorable environment, but only for as long as the rapid change is required. Generalizing this: a successful genepool is one where the mutation rate is "just right" for adapting to the environment. Too much mutation and the genepool isn't stable and will eliminate itself, too little mutation and the genepool will be eliminated by the environment. In this balance, the odds are stacked in favor of avoiding mutation. And all this is orthogonal to the discussion of how cancer (the uncontrolled reproduction of cells) is related to the capacity for mutations (infidelity in the copying process). Cancer resistance and mutation resistance are related, but by no means the same thing. To borrow a computer image: your computer has copy processes with very high fidelity (only the occasional alpha particle to spoil the fun) but this doesn't protect it against worms, which copy themselves unwantedly but with the same high fidelity. This analogy is badly flawed in obvious ways (regular programs are not designed to copy themselves, cells are), but I hope it gets the point across.

anigbrowl 17y ago

Novelty? I have red hair, which I'm not sure is adaptive (eg it puts me at greater risk for skin cancer) but which partners have rated highly as an attractive feature specifically because it's unusual. Then again I have a compulsive draw towards partners from outside my own ethnic group, so there's some selection bias going on with that interpretation.

Tichy 17y ago
I think being attracted to different ethnic groups might have an advantage, too - keeping diversity in the gene pool up is probably beneficial.
- hughprime 17y ago
  Except that in practice, it hardly ever happened until very recently. Ethnic groups lived far apart, and those folks who lived near a boundary between two different ethnic groups would hardly ever interbreed with the others (whether that's mostly cultural or a lack of attraction, though, I'm not sure). Even now, it happens surprisingly infrequently.
  - foldr 17y ago
    >and those folks who lived near a boundary between two different ethnic groups would hardly ever interbreed with the others If you are talking about prehistory, how can you know this?
    - hughprime 17y ago
      Well, inferring from the observed behaviour of stone-age tribal peoples in historical times.
      - foldr 17y ago
        That's a bit vague. Has anyone run the stats on the incidence of cross-tribal sex? And where would they get the data?

breck 17y ago

"Nobody 10,000 years ago had blue eyes," My reaction is that he misspoke here or he overstated his claim to make a point. I know nothing about the proportion of people with blue eyes back then or right now for that matter. But I think at the very least, you could only make that claim with a tiny, tiny, tiny amount of confidence. Maybe the proportion of humans with blue eyes was smaller back then, maybe it was larger, or maybe it was the same. I don't know. But to claim nobody 10,000 years ago had blue eyes is an impossible point to prove unless you have DNA samples from every human alive 10,000 years ago. We might be able to say that all the people alive today with blue eyes descended from one ancestor, but we can't claim to know about the population of people with blue eyes back then. For all I know, half the population 10,000 years ago could have had blue eyes but then got wiped out by swine blue. That's like saying no one 100 years ago was over 7'6" tall. I know a bit more about height and think that this statement may be true. But it would be real hard to prove. Now shift the timespan back by 2 orders of magnitude, and I think it'd be harder to prove. I'm not saying that the general idea is wrong, but I'm just it would be a good idea to question that claim a lot before thinking about reasons why that might be the case.

aaronblohowiak 17y ago
" We might be able to say that all the people alive today with blue eyes descended from one ancestor" -- exactly. And, if you follow the science of using mitochondrial DNA to date genetic changes.. http://en.wikipedia.org/wiki/Molecular_clock http://en.wikipedia.org/wiki/Molecular_clock http://www.livescience.com/health/080131-blue-eyes.html http://www.livescience.com/health/080131-blue-eyes.html
BRadmin 17y ago
All blue eyed people traced to 10000 year old ancestor: http://www.dailymail.co.uk/sciencetech/article-511473/All-blue-eyed-people-traced-ancestor-lived-10-000-years-ago-near-Black-Sea.html http://www.dailymail.co.uk/sciencetech/article-511473/All-bl...
- breck 17y ago
  Interesting. Thanks for the link. Although I'm not convinced from the results of one study, now I understand what the genesis of the original comment was. Evolution is a fascinating subject. I think it would be neat if all our schools taught 12 years of Reading, Writing, Arithmetic and Evolution.

tyn 17y ago

You could just attribute it to the attractiveness of blue eyes. Most people consider blue (and green) eyes more beautiful than eyes with a different color. But this will get you only as far as the next inevitable question: why are blue eyes attractive?

baltoo 17y ago
Status will always be defined by scarcity. Perhaps blue eyes where novel and scares, which could be enough?
rsheridan6 17y ago
Children are have lighter eyes (and everything else) than adults. It's a sign of youth.
- joubert 17y ago
  Huh? Are you saying Blue is a lighter shade of Brown?
  - mmt 17y ago
    Yes, if by "shade" you mean the color progression that human (and other mammals') eyes make in their development.
    - joubert 17y ago
      But your eyes don't change from blue to brown as they develop, or do they?
      - elemenohpee 17y ago
        yep:http://chemistry.about.com/cs/howthingswork/f/eyecolor.htm http://chemistry.about.com/cs/howthingswork/f/eyecolor.htm)
        17y ago

gojomo 17y ago

Speculation in no particular order: (1) Perhaps less pigment in the eyes improves vision in certain conditions (especially those in colder latitudes). (2) As a recessive trait, blue-eyed mating limited a woman's ability to pass off offspring from other (dark-eyed) fathers as that of a blue-eyed father. This greater confidence in paternity won greater fatherly support, and in some eras/places (inheritable property?) this dominates the advantages of promiscuity. (This effect may fade or even reverse depending on proportion of eye colors.) (3) Handicap principle -- even if blue-eyes are a disadvantage in some dimensions (sun-robustness, alien look), sometimes a conspicuous disadvantage is effective as a signal that fitness in other harder-to-measure dimensions is better. ( http://en.wikipedia.org/wiki/Handicap_principle http://en.wikipedia.org/wiki/Handicap_principle ) (4) I suspect just about any unique visible characteristic, advantageous or mildly disadvantageous, can find some reinforcement as a quick signal of genetic kinship against outside competitive groups that look different. So just, "different enough to tell closer-cousins from distant-cousins" could be a sufficient explanation.

tokenadult 17y ago

Beats me. I married someone with brown eyes (and black hair). On the other hand, she married a man with blue eyes (and blond hair), and my genes have been replicated into four children. My dad's genes for red hair have passed on to be expressed in two of my children.

tamas 17y ago
Blue eyes and blonde/red hair are recessive traits, while brown eyes and hair are dominant. You having blue eyes means both of the gene pairs that control eye color have the recessive blue, while your wifes brown eyes can be caused by having a set of blue and a set of brown genes, and as brown is the dominant one, it is what was actually expressed in here eye color. The fact that your children have blue eyes means she does have genes for blue eyes, and they are inherited into your children as well as your blue genes, hence their blue eyes. The same goes for blonde/red vs brown hair. Either that, or consult with your milkman/gardener.
- tokenadult 17y ago
  You having blue eyes means both of the gene pairs that control eye color have the recessive blue, while your wifes brown eyes can be caused by having a set of blue and a set of brown genes, and as brown is the dominant one, it is what was actually expressed in here eye color. My wife is from a part of China that is not very likely to have any genes for blue eyes (or red hair) in the indigenous population. The overwhelming probability is that she is homozygotic for both black hair and brown eyes. The fact that your children have blue eyes means she does have genes for blue eyes There is a reading problem here, because I never said anywhere in my post that any of my children have blue eyes. (In fact, these days I am startled whenever I see a child with blue eyes, even though I grew up with siblings with blue eyes, because all my children and my wife look at me with brown eyes. I see blue eyes and ask myself, "Do they make eyes in that color too?") You also are well advised to do more reading about the genetics of human eye color and hair color http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Human_hair_color http://en.wikipedia.org/wiki/Human_hair_color and human genetics in general. Genes can recombine from one generation to the next. My red-haired dad, by the usual assumption that you made in your reply, was homozygotic for red hair, making me presumptively heterozygotic for red hair, while my wife presumptively is not a carrier of that trait at all, on population genetics probabilities. But two of my children have hair that is "brown" at a glance but also includes red pigment (as can be seen when their hair is backlit by sunlight or when strands of their hair are observed under a microscope). Sometimes children can inherit a double copy on one gene from just one parent, as anyone who has carefully studied human genetics knows. http://www.ncbi.nlm.nih.gov/omim/ http://www.ncbi.nlm.nih.gov/omim/

jordyhoyt 17y ago

How do we know that nobody 10,000 years ago had blue eyes? Er, well, of course it's impossible to _know_, but what leads us to conclude that nobody 10,000 years ago had blue eyes? Anyone know? Edit: posted this before I saw the other thread and the excellent answer here - http://news.ycombinator.com/item?id=824543 http://news.ycombinator.com/item?id=824543 My mistake.

asdlfj2sd33 17y ago

Don't only Caucasians have blue eyes? And aren't they (full disclosure "we" in my case) also the only ones with the mutated version of the gene which controls how much melanin is deposited in skill, hair and... I think also irises? Asians and Africans both have the normal version of the same gene. And melanin has many roles, sun protection being just one, the other is as a structural protein. Just compare how black skin ages vs. how a redhead of the same (advanced) age looks. And why would Caucasians have a mutation which deposits less of such a useful protein? Vitamin D. It is produced when UV light hits the skin. In northern climates with less sun, and skin being covered or you die of exposure, often even when the sun is up, people get a lot less vitamin D. Inuit get more due to their diet, and modern man also gets much more again because of diet. And yet most people living in the north even today lack vitamin D. Also, I thought all of the above is common knowledge which makes me question the whole article.

aaronblohowiak 17y ago
"Don't only Caucasians have blue eyes?" No. More than you ever wanted to know about eyes: http://en.wikipedia.org/wiki/Eye_color http://en.wikipedia.org/wiki/Eye_color Also, this is neat: A 2002 study found the prevalence of blue eye color among Caucasians in the United States to be 33.8 percent for those born from 1936 through 1951 compared with 57.4 percent for those born from 1899 through 1905.[10] Blue eyes have become increasingly rare among American children with only 1 out of every 6 – 16.6 percent which is 49.8 million out of 300 million (22.4% of white Americans) of the total United States population having blue eyes.[33][34] The plunge in the past few decades has taken place at a remarkable rate. A century ago, 80 percent of people married within their ethnic group. Blue eyes, a genetically recessive trait, were routinely passed down, especially among people of Scottish, English, Irish, Welsh, Western and Northern Slavic, and Northern European ancestry.[33][34][35] In the 1930s, eugenicists[citation needed] used the disappearance of blue eyes as a rallying cry to support immigration restrictions. They went so far as to map the parts of the country with the highest and lowest percentage of blue-eyed people.[citation needed]
- asdlfj2sd33 17y ago
  From your wikipedia link: Blue eyes contain low amounts of melanin... Blue eyes are most common in Northern Europe and Central Europe and to a lesser degree in Southern Europe,North America and southern Central Asia; Afghanistan is a notable example.[30] They're also found in parts of North Africa,[31] West Asia, and South Asia[32], in particular the northern areas of India and Pakistan. It can rarely occur as far south as Sri Lanka. However blue eyes are not found within the population of East Asia, due to the major pre-dominance of the brown eye gene in the area. Central Asians, people from the Caucasus, Afghans, Pakistanis, and even Indians darker then many an African are considered Caucasian. They are Caucasians. And North Africa is full of Caucasians, hell even German tribes, Goths if I recall correctly, settled there during Roman times. So only Caucasians have Blue eyes. Again because of a gene mutation which control how much melanin is deposited in hair, skin, and irises. Someone with a lot of melanin could have blue eyes, but they wouldn't appear blue do the the melanin. That's why blue eyes contain low amounts of melanin. And low amounts of melanin are related to vitamin D, which is related to living in northern climates.

kqr2 17y ago

Does anyone know if blue-eyed people continue to have a 5% advantage?

tome 17y ago

It seems to me that amongst (white) people who play badminton, a larger proportion have blue eyes than amongst the general population. A friend told me that in baseball, batters have a higher tendency towards blue eyes, and pitchers to brown, but I couldn't find any references. Does anyone know if this has any scientific basis?

ryne 17y ago

Is there any credit to the rumour that blue-eyed individuals have better sight, indicating why there are so many blue-eyed fighter pilots etc?