Blue eyes going extinct!!! [Passing of the great race]

By Razib Khan | April 10, 2006 5:54 am

No, not really, but perhaps a British newspaper will pick up this meme and I’ll be responsible for a butt-load of misinformation. You gotta get fame somehow! Anyway…
Cohort effects in a genetically determined trait: eye colour among US whites
:

The prevalence of blue eye colour among non-Hispanic whites in NHANES-III was 57.4% (95% CI: 50.1-64.7) for individuals born between 1899 and 1905 compared to 33.8%…for those born between 1936 and 1951. No association was found between survival and eye colour, nor was a cohort effect evident for primary ancestry. However, proportions reporting only one ancestry in census data declined with successive birth cohorts…A secular trend of decreasing assortative mating by ancestry is the likely explanation.

At time 1 you have blue eyes at .57, and time 2 you had it at .34. Assume random mating in time 2 in regards to eye color, so if blue eyes is recessive you have a around .6 (recessive expression needs two copies, ergo, .6X.6 ~ .34) of the alleles in the gene pool cold for “blue.” Well, that’s pretty much what the phenotypic frequency was at time 1, so that implies that all the blue eye genes were in the same individuals at this point (so they are expressed). In fact, time 2 is probably not totally panmictic, so I’m probably overestimating the frequency of blue eye alleles in the population. So something doesn’t add up. This study suggests that 74% of the variation in eye color can be explained by one locus, OCA2.

CATEGORIZED UNDER: Genetics
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Comments (7)

  1. The gap from 1905-1936 is just about the time of the big drop in birthrates. A one-generation time-lag between, say, WASP and Italian birthrate decline could play a role.
    Or, it could be plain wrong.

  2. Reale

    Yes, what a mystery… From 57% down to 34% in less than half a century? Where’d they all go?
    But of course, now I know! Lack of assortative mating? Forget it! This must be where all those blue-eyed sailors have been coming from! My hypothesis confirmed, aaaah how sweet. Now we only have to figure out why they sneak around and infiltrate indigenous peoples. Also, there must be some kind of Central Command taking care of it all, for really, it’s a huuuuge project. I smell a goverment cover-up, probably even an inside job (like 9/11). Yea, perhaps Alex Jones can make a documentary (with Charlie Sheen) about it, this is big news! ^o^

  3. Joane

    “nor was a cohort effect evident for primary ancestry”
    I assume this means the percentages for various ancestries were similar in 1899-1905 and 1936-1951? I find that hard to believe. I would think there would be more Italians and Jews in the 36 to 51 cohort then at the turn of the century.

  4. joan, your point is good, but please note that jews were never more than 4.5% of america’s population, and i don’t think italians were more than that either. also, until 1965 jews had intermarriage rates of around 10%. i think the ellis island wave did have some effect, but i don’t think it can explain these results.

  5. pconroy

    Joane,
    Don’t forget that most Jews arrived from Eastern Europe, and a not insignificent portion of them have blue eyes in fact. I’d have no idea of the percentages, but would guess 15-25%, could be higher.

  6. Boknekht

    Actually, from what i’ve seen myself, American jews do have a very strong tendency toward light irises. Not necessarily blue, but light. Almost every hasidim i’ve ever seen has had light eyes.

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Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

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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