Correlation structure of traits

By Razib Khan | September 21, 2007 11:40 am

kathsheryl.jpgDo any readers know of work which tracks the correlation between characteristics such as blonde hair and blue eyes (within population where these are extant at high frequencies, but not fixed)? I am also interested in geographic distributions. In part I’m interested in exotic combinations, for example, look below the fold….

CATEGORIZED UNDER: Genetics
  • John Emerson

    Razib, these days a lot of women don’t known what their natural hair color is any more. Curb your intuitions.

  • http://akinokure.blogspot.com agnostic

    http://www.biolbull.org/cgi/reprint/18/1/50.pdf
    The last two pages talk about correlation and its inheritance. Study was done (probably awhile ago) on U of Wisc students & families: 71 families, 401 individuals. Says dark hair and light eyes isn’t uncommon, but light hair and dark eyes is rare (they didn’t find any).
    Sherilyn Fenn is only 1/4 Irish, and 1/4 of French, Italian, and Hungarian. So much for being able to use her as an example of hot “dark Irish” girls!

  • cuchulkhan

    Dark Irish hotties are an American myth, probably caused by admixture as Agnostic says. The Irish mean is about as low as Englands.

  • cuchulkhan

    And deceptive Irish last names like Flynn which mask enormous non-Irish ancestry. Did Irish males outmarry more than females in the US, and thus pass on their names more? Abroad, Irish guys tend to be quite successful with the ladies, the gift of the gab and all that, so this is at least plausible.

  • http://scienceblogs.com/gnxp razib

    Did Irish males outmarry more than females in the US, and thus pass on their names more?
    i think they were was some sex bias toward males in the immigrant stream. so likely?

  • President Barbicane

    From high school I seem to recall a black girl who had fairly dark skin, yet had very green eyes. I always assumed that she had a distant white ancestor and inherited the green eye gene (maybe ASPM?). I did wonder at the time if the green eye genes were positively selected. Her eyes were striking.

  • http://scienceblogs.com/gnxp razib

    . I always assumed that she had a distant white ancestor and inherited the green eye gene (maybe ASPM?)
    green is on OCA2.

  • Neziha

    There’s a serious complication with this sort of research in, as often hair and eye color(in populations where this is variable) are -not- static throughout the life. Many whites are born blond, and their hair darkens as they get towards adulthood. So a blond haired blue-eyed kid may turn into a brown-haired blue-eyed adult. I’ve also heard anecdotally(no idea of truth) of a rare Slavic(?) trait where dark hair in childhood turns red in adulthood. Some hair sunbleaches, and so is different colors seasonally. Chemotherapy can change hair texture and color. Not to mention normal greying. Eye color can change too, naturally or otherwise. There’s a glaucoma drug that turns eyes brown…
    There’s a reason these traits haven’t been fully figured out yet…they give people headaches.

  • http://scienceblogs.com/gnxp razib

    There’s a reason these traits haven’t been fully figured out yet…they give people headaches.
    75% of blue vs brown eye color variation is localized to OCA2. read about it here.

  • http://www.ninapaley.com Nina P

    What gene is responsible for the metallic skin in the video? That is exotic.

  • http://entitledtoanopinion.wordpress.com/ TGGP

    Speaking of odd combinations and geography, how common is blondism among Turks? In the film Head On/Gegen die Wand/Duvara Karsi Sibel’s mother (who is supposed to be a Turkish immigrant) has that kind of hair, but I can’t recall any other Turks having that. In the movie they are supposed to be very traditional, so it would be odd if it was supposed to be dyed.
    I actually didn’t notice anything odd about Rihanna (other than the obvious photo-magic applied to the video), which I guess just goes to show my powers of observation.

  • http://akinokure.blogspot.com agnostic

    Re: Turks, I’ve only seen a very biased sample — the uber-elite from Istanbul who attended an elite US college — but light hair among them seemed about as common as among other European Mediterranean areas. Their facial features are also garden variety Mediterranean, not Central Asian (I only saw on girl who looked Central Asian). I’m trying not to go off on a tangent about how stunning these elite Turkish girls are…
    Not knowing much Turkish history, I’d guess that the elite there historically weren’t influenced that much genetically by the Turkic groups, but adopted their culture, language, etc., somewhat like the Hungarians did with the Magyars.

  • http://scienceblogs.com/gnxp razib

    Not knowing much Turkish history, I’d guess that the elite there historically weren’t influenced that much genetically by the Turkic groups, but adopted their culture, language, etc., somewhat like the Hungarians did with the Magyars.
    the highest number i’ve seen is around 20% of central asian ancestral load. but usually closer to 10%.
    also, look at the maps
    http://www.gnxp.com/blog/2006/03/blonde-hair-blue-eyes.php

  • Keith

    I have never seen numbers to back this up but it seams to my biased eyes that the combination of blue eyes and black hair is quite common in the West of Ireland. I am a example of it myself and growing up there i knew lots of people with the same combination, its not the result of a admixture of different nationalities as the region has seen little immigration up until the last few years.

  • http://scienceblogs.com/gnxp razib

    I have never seen numbers to back this up but it seams to my biased eyes that the combination of blue eyes and black hair is quite common in the West of Ireland. I am a example of it myself and growing up there i knew lots of people with the same combination, its not the result of a admixture of different nationalities as the region has seen little immigration up until the last few years.
    you can find confirmation in the old anthropological literature.

  • http://www.mikekeyes.com mikeyes

    razib said:
    “Did Irish males outmarry more than females in the US, and thus pass on their names more?
    “i think they were was some sex bias toward males in the immigrant stream. so likely?”
    Razib,
    The Irish immigration overall had more women than men in it (http://politics.as.nyu.edu/docs/IO/4600/kaminsky_thesis.pdf) and in comparison to many other immigrant groups the Irish were closer to 50/50. This is fairly well known amongst the historians of Irish immigration (at least they taught that to me) and I think it is born out by the immigration records.
    As for “dark haired blue eyed Irish beauties”, certain parts of Ireland, such as the tip of the Dingle peninsula (a rural and until recently isolated area), abound with them.

  • pconroy

    Mike,
    I believe that after the great wave of Irish emigration during and immediately after the famine (1840-50′s), that there was a period in the 1870-1890 when a lot of young, unwed Irish girls came to the US, as household servants – in some places taking the jobs formerly done by African-American domestic slaves.
    I know that in New York city, there seems to be a disproportionate number of marriages between Italian men and Irish women, but Irish men and German/Polish women. In other words Irish guys are marrying blonde, more feminine women, whereas Irish women are marrying darker, more macho men?!

  • Mikeyes

    I think that even in the famine years there were at least 35% women in the mix. Most other immigrant populations had a preponderance of men. You are correct in saying that a large number of Irish women came over in the later years of the immigration to the states (which probably ended in numbers when they changed the laws 40 or so years ago), but there were significant numbers of women in the famine years too. (My family being a good example of this – all of the original immigrant men married immigrant Irish women. But that is not scientific proof, I grant.)
    I suspect that the main reason that Irish women married Italian men (in the absence of Irish men) is that the church mandated that you marry within the fold and the only place to meet Catholic men would have been in church. A good reason to go to church.

  • Lucius

    Only 10% of Turkish people have black hair. I’v been studiying Turkish history for 6 years now and I’v only seen very few black haired Turkish people in Turkey. What I dont get is that why do the Turkish people in europe have dark brown or in some cases black hair.

  • mardi

    I have black hair and blue eyes, my heritage is mostly english but i’m quarter Italian,but i think i got my dark hair and light eyes from my fathers side, which is mostly english…though there could be a little Irish if you go way back.
    I also have 2 cousins on my fathers side..sisters..one has dark hair and blue eyes and the other has blonde hair and brown eyes, their of german ancestry on their fathers side.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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