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Engineers Have More Sons, Nurses More Daughters

Posted by Hemos on Mon May 23, 2005 11:40 AM
from the but-what-about-female-engineers-and-male-nurses dept.
Science
Bifurcati writes "While it might be irrelevant for many /.ers, a recent study has shown that people in stereotypically male professions (engineering, IT, mathematics, etc) are more likely to have sons than daughters, while nurses, therapists and teachers tend to produce more girls. Based on independent survey data, engineering types produce 140 boys to every 100 girls, while nurses and the like produce 135 girls to 100 boys. The explanation is unclear, but it might have interesting long-term social implications. A more detailed summary of the journal article is available on Illuminating Science."
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  • diet can affect gender... (Score:5, Funny)

    by professorhojo (686761) * on Monday May 23 2005, @11:42AM (#12613165)
    Studies have shown that a mother-to-be's diet high in calcium and magnesium including milk, beans, cereals, cheese and nuts may favor a baby girl, whereas a diet high in pizza and coke apparantly favors the conception of a baby boy.

    • Interestingly, so can dominance-submission of the father. The theory is that dominance or submision will be passed on to the child either through genetic or envrionmental factors. Result is that a dominant male child will get around a lot and have many kids whilst a submissive male will not get many mates. Therefore, if you're dominant, best to have a male child and if your low-status, best have a girl as she's going to get laid anyway.

      Relating it to the story? Engineers are clearly high status individuals. So get out there, boys. ;)
    • I take it thats prior to conception ? as the sperm contains the other Y or X chromasome..
      Or does it cause conditions such as XX males and XY females?

      • Re:diet can affect gender... (Score:5, Informative)

        by Rei (128717) on Monday May 23 2005, @12:03PM (#12613509) Homepage
        The parent was joking (and I'm surprised that so few have caught it), but apart from that, gender is not simply tied to chromosomes. In fact, there's only one small section of the Y chromosome that causes virilization (SRY) (of it, only one or two genes start the process), and this has been known to migrate on occasion to other genes. There have been a number gender-affecting of mutations that have occurred in the region (including, in one case that I read, a two BP mutation that caused a normal XY female. In another case, a normal XX man didn't even have a migrated SRY, but simply had virilized from other, unknown effects.

        Environmental factors can play a strong role, and might have been involved in the latter case. Excessive androgens produced by the mother can lead to degrees of virilization of the fetus; other factors may help cause androgen insensitivity and thus feminization. Gender isn't so clear cut; it just tends to migrate to one extreme or the other because that's genetically advantageous, and the Y chromosome usually acts as a carrier for the genes that activate virilization.

        As for what's causing the "engineer shift", that's a really good question... that's a pretty darn big correlation that the article described.
      • Well you generally have an equal number of X and Y sperm (while all eggs are X of course) its been shown that Y sperm die easier when conditions are harsh (acidity, not right temperature etc.) and are stronger when conditions are just right. So this affects the gender greatly. How brain-type affects gender is unknown but probably based on hormons levels which can change these conditions.

  • Finally I know (Score:5, Funny)

    by vlad_petric (94134) on Monday May 23 2005, @11:42AM (#12613168) Homepage
    That's why they do the graduate engineering/nursing mixers!

  • Irresponsible statistics (Score:5, Insightful)

    by metachor (634304) on Monday May 23 2005, @11:43AM (#12613178)
    Repeat after me: "Correlation does not imply causality."

    • Re:Irresponsible statistics (Score:5, Funny)

      by shaka999 (335100) on Monday May 23 2005, @12:04PM (#12613520)
      Repeat after me

      "I'm a science wenie and need to get out more."

      The article doesn't draw conclusions. Its just an interesting set of data.

      • Re:Irresponsible statistics (Score:5, Interesting)

        by Anonymous Coward on Monday May 23 2005, @12:40PM (#12614147)
        The question, of course, is whether this is a reasonable interpretaiton of an objective set of data, or whether this is pseudostatistics where you start from a conclusion, and work backwards to find it in the numbers. Some questions I'd like to see addressed:

        * How were the groupings into "masculine" and "feminine" professions done? Is this reasonable, and did they truly choose the most "obvious" masculine and feminine professions to include?
        * Do these groupings span the dataset, or are some (possibly most) professions excluded as "neutral"?
        * What is the breakdown by profession for all professions, not just the included groups?
        * Most importantly, was the selection of the "masculine" and "feminine" professions determined BEFORE or AFTER the data was collected?

        My concern here is that they started with a dataset for chilbirth for all professions (probably on a fairly small dataset). They noticed some professions skewed one way, some another. They noticed that some of the professions skewing male were "masculine" and some skewing female were "feminine" and called it a conclusion, sweeping all the other anomalites in their dataset under the rug. Hey, presto! Conclusion!

        Fact: The general benchmark for "statistical significance" is 95% confidence that the data cannot be explained as a random phenomenon.

        Experiment: Create 20 hypothetical correlations to test for on a completely random dataset. On average, you should find one in twenty hits the 95% confidence mark.

        Intellectually dishonest followup: Publish your one statistically significant result with great fanfare. Bury the othe 19 in a footnote, if you mention them at all.

        Step 3: Profit!

    • I don't see where they're saying that becoming an Engineer will guarantee you a son. They're noting the correlation and nowhere implying a causality.

      Repeat after me, "Lack of causality does not make the correlation insignificant."

    • Repeat after me: "Correlation does not imply causality."

      And the Internet as a whole is a terrific place for posting as fact misreadings of misinterpretations of things people don't say. (No, not you.)

      The original paper [sciencedirect.com], which was a study based on a few thousand people, was looking at extreme male-brainedness in autism. They picked out profession as an indicator of male-brainedness. The data for sex of the offspring was available only one year (1994) of the data they had.

      They also selected th

      • Wrong. (Score:3, Informative)

        by XanC (644172)
        Couples desperate to produce a son could boost their chances if one or both of them switches to a "masculine" profession such as engineering or accountancy, a report has said.

        • Re:Wrong. (Score:5, Informative)

          by ProfaneBaby (821276) on Monday May 23 2005, @11:51AM (#12613301)
          From the first link: The study did not say why this phenomenon occurred

          From the second: They're very cautious about interpreting the cause of their results, and what conclusions could be drawn.

          Read past the first line teaser. The meat of the article isn't nearly as bad as one would like to pretend.

        • Not Wrong - Look at the bloody context (Score:5, Informative)

          by GryMor (88799) on Monday May 23 2005, @11:52AM (#12613327)
          Of course, the media has promptly taken things one step further and suggested that "Couples desperate to produce a son could boost their chances if one or both of them switches to a "masculine" profession such as engineering or accountancy". Perhaps this is true - but that might be reading more into the report than is good for it.

      • Re:Correlation is fine here. (Score:4, Funny)

        by maxwell demon (590494) on Monday May 23 2005, @11:59AM (#12613438) Journal
        Well, XX sperm would cause ill childs anyway (namely XXX womans, unlessa the egg cell has an anomaly itself).

        However, solving equations of course favours Y chromosomes. That's because you always solve after X, so you have its actual value and therefore can eliminate it. Eliminating X of course doesn't affect sperms with an Y chromosome (because it doesn't have an X to eliminate), but only sperms with an X chromosome (after all, x is exactly what you eliminate).

        SCNR :-)
      • I agree! Especially since the male ALWAYS determines the sex of the child.

        Not strictly true.

        For starters, X and Y bearing sperm are affected differently by envrionmental factors (such as pH) which has been used in vitro to strongly bias fertilization toward one sex or the other. The female provides the environment (including pH) in which the sperm swim.

        There are plenty of other ways a woman's body COULD bias the outcome. Anitbodies - leading to reduced sperm mobility or higher likelyhood of spontaneou
      • I agree! Especially since the male ALWAYS determines the sex of the child.

        This is simply not true except in the most simplistic sense. Sperm counts (according to the wikipedia) have a normal range of 20 to 180 million per millileter. There are countless sperm carrying both the X and Y chromosone vying for the prize.

        There are subtle differences between X and Y bearing sperm in robustness and mobility, IIRC; it is possible that the male can influence conception sex by producing sperm of each type that ar

  • Causality (Score:5, Insightful)

    by XanC (644172) on Monday May 23 2005, @11:44AM (#12613191)
    The article seems to imply that by switching to a masculine job, you'll change the sex of your potential children.

    I think it's far more likely that it's not what job you're doing, it's what job you tend to want to do.

    • It IS what job you're doing... (Score:4, Interesting)

      by raehl (609729) <raehl311.yahoo@com> on Monday May 23 2005, @12:22PM (#12613803) Homepage
      Or more importantly, who is doing it.

      We have two groups of children: One group has a parent who is in a "male" profession, like engineering, and the other has a parent in a "female" profession, like nursing.

      What is far more likely to be true of a child with a parent who is in a female profession as opposed to a child with a parent in a male profession?

      They're more likely to have a mother who works.

      Seems pretty obvious to me: Working moms are more likely to have girls. Might have something to do with Y-chromosome sperm being more fragile than X-chromosome sperm. (That's been demonstrated elsewehre.)

  • World Domination! (Score:5, Funny)

    by Lordofohio (703786) on Monday May 23 2005, @11:44AM (#12613193)
    Just the news I need to hear in order to start my line of supersmart offspring that will form the ultimate Revenge of the Nerds. Mwuhahahahahahahha

    Oh wait, according to my calculations the probability of me getting laid is 3x10^-8

  • Simple explanation (Score:5, Funny)

    by justforaday (560408) on Monday May 23 2005, @11:44AM (#12613194)
    Duh! It's because boys have boys and girls have girls. Oh, wait...

  • Needs a lesson in genetics. (Score:5, Informative)

    by Eunuch (844280) * on Monday May 23 2005, @11:44AM (#12613197)
    More testosterone in the womb leads to boys.

    What does this have to do with the father? What does this have to do with which sperm gets into the egg?
  • Crap, I was looking forward to having 1 boy, and 1 girl. Now I find out I need 1.4 boys, until I can have my 1 girl.

  • correlation and causations (Score:4, Insightful)

    by haluness (219661) on Monday May 23 2005, @11:44AM (#12613201)
    This really seems like an interesting ratio that popped outof some calculations, i.e., nice, but not really meaningful.

    I mean, how would somebodies profession really determine his/her childs' sex? I'm sure that mining other datasets would lead to similar 'interesting' ratios/facts.

    As has been mentioned on /. and other places - correlation is not necessarily causation.

    • Re:correlation and causations (Score:4, Insightful)

      by cpotoso (606303) on Monday May 23 2005, @12:11PM (#12613635)
      The reason, if any, could be as follows: a couple with more "masculine traits" may stop having children after they get a boy, whereas a "more feminine" couple stops having children after having a girl. Lets enumerate the possibilities.

      For the "masculine couple" (please note that the following are not equal in probability!):

      BOY, stop

      GIRL, BOY, stop

      GIRL, GIRL, BOY, stop

      etc.

      A similar (substituting BOY and GIRL) sequence can be made for the "feminine" couple.

      It is easy to see how this would lead to more BOYS or GIRLS in each respective case (on average).

      This is one possible explanation of cause.

      • Re:correlation and causations (Score:5, Insightful)

        by egomaniac (105476) on Monday May 23 2005, @02:30PM (#12615936) Homepage
        It is easy to see how this would lead to more BOYS or GIRLS in each respective case (on average).

        Not so. Assuming you have a 50-50 chance of it being a boy or a girl, you will end up with 50% boys and 50% girls no matter what contortions you go through to try to influence the outcome.

        Look at it another way: pretend these are coin flips rather than childbirths. Your suggestion (that you can alter the odds by when you choose to stop trying) is equivalent to saying that you can bias to heads or tails by deciding when you stop flipping the coin. And, of course, that isn't true -- no matter how many trials you perform or in what order, a fair coin will (on average) deliver 50% heads and 50% tails. One more 50-50 flip won't in any way alter the expected outcome.

        It's exactly the same way with childbirth. The first child (we would expect) would be 50% likely to be a boy. The second would be 50% likely to be a boy. The third would be 50% likely to be a boy, and so on ad infinitum. Adding another trial (childbirth) onto the end of the sequence does not change the odds, and on average you would end up with 50% boys and 50% girls.

        Of course, this research shows that that naive assumption isn't true, and apparently something is altering the odds. We just don't yet know what.

        (And, amusingly enough, I'm to find out my baby's gender in two days. Evidently it's more likely to be a boy...)

  • And I married a nurse (Score:5, Funny)

    by BronxBomber (633404) on Monday May 23 2005, @11:47AM (#12613237)
    While this study is most assuredly crap, (I dont see what these "long term social implications" really are), its pretty interesting.

    Hopefully (we dont have children yet), I'll have a healthy boy or girl, who will take great care of me AND my source code in my very old age.

    • Your source code? I've never been given my source code, and even the binary (well actually the quaternary, given that it is encoded in base 4) is locked away in the cell nucleus in a form which is not easily accessible.

  • Shettles Method (Score:5, Interesting)

    by iammrjvo (597745) on Monday May 23 2005, @11:48AM (#12613260) Homepage Journal

    There are proponents of different techniques that supposedly let you choose the sex of your child. One interesting technique is called the Shettles Method [google.com]. One family that I know swears by this method. They are four for four in getting it to work.

    At any rate, perhaps different personalities or lifestyle conditions between engineers and nurses would help to explain this data - if indeed there is any credence to Shettles or similar methods.

  • Oh, yeah... (Score:3, Funny)

    by zerbot (882848) on Monday May 23 2005, @11:53AM (#12613344)
    The study did not say why this phenomenon occurred, but The Sunday Times quoted a specialist in evolutionary psychology as saying it could be because the children of "systemiser" parents appeared to encounter more testosterone in the womb, making their gender more likely to be male.

    We know what these psychologists were doing in biology class, and it wasn't paying attention to what was being taught.

  • Easy explanation! (Score:5, Funny)

    by behoward (720454) on Monday May 23 2005, @11:57AM (#12613398)
    Easy explanation: people in stereotypically male professions, except for jocks, are less able to attract an attractive mate. This sad fact leads them to disproportionately engage in sex using the "doggy" position to avoid looking at each other's ugly faces. And, as has been proven, this results in semen getting in closer to the egg where the male sperm can impregnate. Face-to-face intercourse requires sperm to swim farther, giving the advantage to the female sperm, which have greater stamina and can impregnate after all the wimpy male sperm have died out.

  • Summary of the actual article (Score:5, Insightful)

    by call -151 (230520) * on Monday May 23 2005, @11:58AM (#12613417) Homepage
    Both of the linked articles are pretty flismy- the first claims that switching professions may increase the chance of having a child of a particular gender (confusing correlation with causation...) and the second one marvels at the notion that a sequence of children of the same gender is more likely than randomness would suggest (which is already well-established as there is some genetic predisposition towards male sperm having uneven fractions of X and Y chromosome shares).

    The actual article (Journal of Theoretical Biology, 233, p589-599 "Engineers have more sons, nurses have more daughters: an evolutionary psychological extension of Baron-Cohen's extreme male brain theory of autism" by Satoshi Kanazawa [lse.ac.uk] and Griet Vandermassen [ugent.be] and available through Elsevier's Science Direct [sciencedirect.com]) came out in December 2004 an is available online for those whose institutions subscribe, notes the following correlations:

    This is based on survey data from US professions of around 1500 people. Only some of the professions are categorized as "systemizing" and "empathizing" so presumably the sample size is much smaller than that . The sample size isn't listed directly in the article but it appears to be about 20% of the 1500 with at least one parent so categorized profession, for around 300 people or so. Most professions are neutral in the "systematizing/empathizing" continuum, apparently.

    Amoung those with "systemizing occupations" had regression coefficients of .35 with the number of sons and .14 with number of daughters, and those with "empathizing occupations" had coefficients of .27 with #sons and .40 with #daughters. (As a side note, it appears that "empathizing professions" have more reproduction overall, consistent with common myths about lonely geeky engineers...)

    From the classification of professions:


    Systemizing occupations

    • Executative, managerial, adminstrative such as financial managers, analysts, etc.
    • Professional: architects, engineers, etc.
    • Technicians


    Empathizing occupations

    • Professional: nurses, speech therapists, teachers, counselors


    Presumably other professions are regarded as neutral in this spectrum.

  • babies sex can be influenced. (Score:4, Interesting)

    by WindBourne (631190) on Monday May 23 2005, @12:09PM (#12613606) Journal

    There is no doubt that a babies sex can be influenced by a number of criteria. Male sperm tends to be faster, but live shorter lives. Female sperm is hardier, but slow. So a women who is slightly acidic or base will tend to kill the male sperm leaving female sperm. Likewise, if traditional sex prevails (male on top) with a laying around afterwards, then male has better chance (shorter distance, as gravity helps carry the sperm further up (BTW, so does a women's orgasm). But if women on top, then sperm has further to go, so more likely that female sperm wins.

    So why relevant? Nurses, teachers, etc have a healthier attitude about sex. More likely the women are on top (or at least have a varied sex life). Girl wins.
    Engineers are more conservative, so more likely to be on top. Boy wins.

  • The reverse (Score:3, Interesting)

    by Carewolf (581105) on Monday May 23 2005, @12:09PM (#12613614) Homepage
    I saw a danish study last year that proved the opposite. They had only studied the fathers since it is the sperm that decides the sex, and clearly showed that men in male dominated workplaces had more daughters.

    The exact same thing has been demonstrated in many animals with the interpretation that we are unconsciously trying to fix the perceived sex ratio.

  • Nurses stand up, Engineers sit (Score:3, Insightful)

    by e1618978 (598967) on Monday May 23 2005, @12:19PM (#12613760)
    Maybe you generate more girls if you spend a big chunk of your day standing and walking around.
    • My wife was a nurse before becoming a teacher. So far we have 1 daughter.

      So clearly I need to spend some more time at a computer if we're ever going to have a boy... oh, wait.

      I think the real reason is some engineers even manage to scare off their own X sperm.
    • Male sperm is more abundant but weaker than female sperm. So in an amenable environment, male sperm are more likely to implant and reproduce. In a hostile environment, the hardier female sperm are more likely to survive.

      I'm therefore not at all surprised by the result that couples are more likely than chance to have "more of the same" sex children.

      I also would not discount the testosterone theory out of hand.
    • Of course, the media has promptly taken things one step further and suggested that "Couples desperate to produce a son could boost their chances if one or both of them switches to a "masculine" profession such as engineering or accountancy". Perhaps this is true - but that might be reading more into the report than is good for it.

      Short people, if they switch to being tall, can improve their chances of having tall children.

      Engineers aren't in their profession by accidentally not becoming nurses or teacher

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