Brown eyed girl?

Share on FacebookShare on Google+Email this to someoneTweet about this on Twitter

Peter Frost states:

I suspect there is some incipient sex-linkage, i.e., European women may be somewhat likelier to have non-brown eyes and non-black hair. If this sex-linkage is mediated by prenatal estrogenization there may also be some impact on personality and temperament. But I really don’t know, and unfortunately there are still more questions than answers.

I’ve read Peter’s book, Fair Women, Dark men, and it is a great collection of data. Also, he has theorized that European color variation is a byproduct of selection selection. So I have been primed to look for a trend where women seem to express blondism or light eye color at higher frequencies. But I just haven’t found anything like that. In fact, I’ve found data which goes in the other direction, that is, females have a higher frequency of brown eyes! But this really clinched it for me:

The source is this paper, Genetic determinants of hair, eye and skin pigmentation in Europeans. Note that women tend to score higher on skin sensitivity toward sun, which implies that they do have ligher skin. And as for hair color, well, perhaps there is a difference in how one judges blonde vs. brunette for males and females? I don’t know. But the eye color data I’ve seen elsewhere and just dismissed it as small N or something like that. At this point my assumption is that there isn’t really the sexual dimorphism in eye color that there is most definitely is in skin color. As for hair, I’m more open to this since it seems that it is subject to more genes, and there could be some hormonal factor as the tendency toward greater blondism in children and females is noted among Australian Aboriginals as well.

Anyway, forget visual inspection. Here’s the associations taking sex into account (from Table 4 of supplementary info):

The authors don’t want to make a judgment based on these data. But I’m not religious about 0.05 P values. And it looks like there’s some action on KITLG anyhow.

Labels: ,

20 Comments

  1. This is the pattern also in Sweden and Finland (I could dig up references, but they’d be useless for those who don’t speak the right languages). Females have darker eyes. 
     
    Anecdotally, I know of brown eyes running in the females but not the males of a family and I’ve never heard of it happening the other way around. 
     
    And as for hair color, well, perhaps there is a difference in how one judges blonde vs. brunette for males and females? 
     
    Women tend to have longer hair. That changes the appearance and the actual colour of the hair, as the hairs on a long-haired person have been hanging there getting the sun and the elements for years. (If you want to learn a sure trick for telling natural blondes from fakes, look at the roots – natural blondes are _not_ the same colour along the whole length of the hair. Some *very* blonde people are the exception, but adults are only rarely that blonde.) 
     
    (Of course, when eyeballing a crowd, there’s an obvious illusion – hair darkens as people age and with women the eye tends to notice the young ones…)

  2. This is the pattern also in Sweden and Finland (I could dig up references, but they’d be useless for those who don’t speak the right languages). Females have darker eyes. 
     
    one of my links is to finnish data. so yeah, i’ve seen it. i saw in other older anthropological data as well. i dismissed it because i knew that on skin color women are lighter and what not.

  3. Forget the brown eyes, which really aren’t very different — it is amazing the excess of *green* and deficit of *blue* eyes in women compared to men. It’s extreme enough that I would expect an X-linked modifier gene. But none of the candidates so far are X-linked.

  4. yeah, why so many more green-eyed ladies than men?

  5. It is quite amusing to imagine a researcher trying to discover the real, natural, undyed colour of a woman’s hair. Nothing harder.

  6. Males across all cultures score lower on 4 of the 6 facets of Extraversion (for the Big Five’s questionnaire, the NEO-PI-R), and higher than females on 2 of them. It’s a robust pattern. The facets of E that males score lower on are the love / gregariousness ones, and the ones they score higher on are the dominance / novelty-seeking facets. 
     
    So maybe we should look more at the correlation between eye, hair, skin color with facets of personality traits, not just the broad factors. Light eyes might make you less of an outgoing chatty cathy, and maybe lighter skin makes you less dominant and excitement-seeking. That would fit with men having lighter eyes yet darker skin. Might also explain why Europeans have lighter eyes and skin. 
     
    Tx for the pic of the brown fly honey — you’re breaking your own rules! ;)

  7. it is amazing the excess of *green* and deficit of *blue* eyes in women compared to men 
     
    I wonder if pretty boys are more likely to have green eyes, then… using an N = 1, I would say yes (if hazel-green counts).

  8. Doesn’t Frost push off the idea of there being some innate preference for light skin? IE, the idea that dark skinned individuals are at a huge disadvantage in the mating game? 
     
    Why would you cite something that malicious? 
     
    Either way, light hair and eyes would serve as an indicator here.

  9. Doesn’t Frost push off the idea of there being some innate preference for light skin? IE, the idea that dark skinned individuals are at a huge disadvantage in the mating game? 
     
    it’s more complicated than that. read his book or his web site. in short, he emphasizes preference for lighter-skinned females within the population average
     
    Why would you cite something that malicious? 
     
    what’s malicious about that? it’s a preference. it hurts a lot of feelings, but is doesn’t imply ought. the issue isn’t if it hurts feelings or not, the issue is whether it is true.

  10. Suppose that we start with an ancestral population in which all individuals have the “standard” human coloration: brown/black hair and brown eyes. What are the reproductive prospects of a mutant individual in this population who has blue eyes or blonde hair? Will anyone want to mate with this freak? My naive expectation is that such a mutant allele would be eliminated from the population by sexual selection. So, the question which interests me is the following: What was so special about the Scandinavian/Baltic region that prevented mutant alleles from being suppressed?

  11. My naive expectation is that such a mutant allele would be eliminated from the population by sexual selection.  
     
    remember that blondism and blue eyes tend to exhibit some recessivity. so it is likely subject to neutral forces initially and will usually just go extinct. you need meta-population dynamics and some inbreeding within demes for the initial increase of frequency for the traits to be due to direct selection (that is, the frequency of the alleles need to jump up through drift very quickly so that they express in much of the population). 
     
    So, the question which interests me is the following: What was so special about the Scandinavian/Baltic region that prevented mutant alleles from being suppressed? 
     
    the alleles which result in blonde hair and blue eyes also contribute to some of the average effect in regards to skin color. my own suspicion then is that skin color (light) is being selected for primarily. some people point to the baltic area as the highest latitude area with agriculture, so low vitamin D consumption in diet + very little sunlight -> need for very light skin. there could be plenty of other secondary effects, but note that selection for OCA2 is very recent (this is the ‘blue eye gene’). the area around KITLG, blond vs. brown hair, also seems to have been hit, though perhaps not as recently (doesn’t show up in haplotter, though empirical p value is low, but does show up in williamsen et. al.).

  12. yeah, why so many more green-eyed ladies than men? 
     
    Has self-reporting been controlled for? 
     
    Just got a bit suspicious after finding poll results at the Finnish Cosmopolitan site (presumably mostly female) where 22% claimed to have green, 17% blue-green and 5% green-brown eyes. That’s 44% shades of green which sounds a bit high to me. (The rest: brown 12%, blue 24%, blue-gray 14%, other 3%). Could women be reporting slightly “fancier” eye colors more often?

  13. The problem with this kind of data is that sex differences in pigmentation interact with age. This is true for skin color (which becomes sexually dimorphic at puberty) and is probably true for hair color (male hair color seems to darken faster than female hair color after puberty, see Steggerda, M. (1941). Change in hair color with age. Journal of Heredity, 32, 402-403). 
     
    To date, I haven?t come across a study that measures eye color as a function of both sex and age. 
     
    The unpublished British study found that brown-eyed participants had lower digit ratios than those with other eye colors. That seems to suggest increased prenatal estrogenization among people with non-brown eyes. Again, this study was never published, but its weaknesses related to the hair color data, not the eye color data.

  14. peter, but that wouldn’t be an issue in the eye color for the direction you are talking about. unless they used old women and young men, i guess. that seems unlikely, but i guess someone could check the paper if they noted anything weird like that.

  15. So, it looks like Nordic women tend to have fairer skin but the same color hair as men. Eyes tend to be the same, except that green eyes replace blue eyes in a lot of women. 
     
    Is there a link between red hair and green eyes — it’s such a striking combination that I wonder whether it was sexually selected for or against.

  16. “what’s malicious about that? it’s a preference. it hurts a lot of feelings, but is doesn’t imply ought. the issue isn’t if it hurts feelings or not, the issue is whether it is true.” 
     
    It’s malicious because it emphasizes something that disadvantages the vast, overwhelming majority of humanity. IE, the idea of a light skin preference being innate.

  17. Suppose that women prefer males over 6′ tall. It’s malicious because it emphasizes something that disadvantages the vast, overwhelming majority of humanity. IE, the idea of a height preference being innate. 
     
    Suppose that women prefer males with IQ > 120. 
    It’s malicious because it emphasizes something that disadvantages the vast, overwhelming majority of humanity. IE, the idea of intelligence preference being innate. 
     
    Etc. The argument is both silly and pernicious. 
    Facts are chiels that winna ding, 
    And downa be disputed.

  18. It’s malicious because it emphasizes something that disadvantages the vast, overwhelming majority of humanity. IE, the idea of a light skin preference being innate.One of the hallmarks of ‘magical’ thought is the inability to distinguish between thinking or talking about a thing, and making that thing real. 
     
    Whether there is an inherent preference for light skin or not, suggesting that this preference may exist will not cause anyone to become more disadvantaged than they already are.

  19. The problem with this kind of data is that sex differences in pigmentation interact with age. This is true for skin color (which becomes sexually dimorphic at puberty) and is probably true for hair color (male hair color seems to darken faster than female hair color after puberty, see Steggerda, M. (1941). Change in hair color with age. Journal of Heredity, 32, 402-403). 
     
    here is where they got the samples: 
    A total of 2,986 Icelandic adults, recruited through cardiovascular, neoplastic, neurological and metabolic studies, were genotyped 
    for 317,511 SNPs using the HumanHap300 BeadChip (Illumina).
     
     
    and 
     
    The Dutch sample was composed of 696 males recruited for a prostate cancer study36 and 518 females recruited for a breast cancer study by 
    the Radboud University Nijmegen Medical Centre (RUNMC) and through a population-based cancer registry held by the Comprehensive Cancer Centre 
    IKO in Nijmegen.
     
     
    i’m assuming that the dutch sample would be older. but neither group would be of super-young people in all likelihood. so i doubt that age effects could explain the within-group differences above (unless you’re asserting that the effect you are curious about only applies to say 15-30 year olds or something and eye color changes from adolescence to middle age).

  20. I think there is definitely a preference for lighter skinned women within the population as mentioned above. Lighter skinned women in general – no. Even anecdotally we know many men do not like extremely pale women. We also know many pale men like tanned women. But how many black men like snow white women (including albinos in their own populations) etc. (using this as an extreme case, i.e., light skin not within the population). How many white women like pitch black men? Not many, for both. The light skin/dark skin thing with men and women is pretty meaningless this day in age. Maybe thousands of years ago…

a