Where junk science comes from

Did you know that intelligence is produced by genes that are located on the X chromosome? I didn’t. In fact, I know of a lot of evidence that directly contradicts that absurd idea. So where did that strange claim come from?

Start here. A local television news station in Sacramento reports on Study: Children get their intelligence from their mom. They make a remarkable claim.

Since women carry two X chromosomes — that’s where intelligence genes are located — several studies have found kids are twice as likely to inherit their intelligence from their mom.

Yes, your dad may give you some intelligence genes, but the study says they won’t have an affect on your brain. The genes will only work if they come from your mom because they will go directly to the cerebral cortex. Genes from the father’s side go to the limbic system.

But none of that is true! “Intelligence genes”, whatever they are, are not discrete entities located on just the X chromosome, and it doesn’t make much sense to claim that kids are twice as likely to inherit intelligence from their mothers. Every boy has one X chromosome that they inherited from Mom, and every girl has one X from Mom, and one X from Dad. And what are these “several studies” that did this work? They don’t say.

That second paragraph is pure gibberish. Maternal genes “go” to the cortex, while paternal genes “go” to the limbic system? This makes no sense. You have to watch the report to believe it, though: to evaluate this claim, the reporter calls up his mom to ask her if he got his brains from her, and then goes to a toddler tumbling class to ask random moms if they agree. Science!

You might be wondering, what study actually makes that original claim? They actually have a link to that, but more about that in a moment.

Let’s look in on that hive of blithering mendacity, gossip, and side-boob shots, the Huffington Post. They report on the same “study”, saying Intelligence Gene: Science Proves Moms Are Responsible For Kids’ Smarts. Don’t you just love that phrase, “science proves”, especially when it’s immediately followed by some bogus nonsense?

The genes that carry intelligence are located on the X chromosomes. And since women carry two, it’s more likely that children get their brain power from their mom as opposed to pops.

But while some dads may brush this off, it’s actually extremely unlikely that their intellect has any impact on their kiddos.

“If that same gene is inherited from the father, it is deactivated,” the study reported.

There’s that mysterious the study again. What study? I’ve never seen a study that shows that intelligence is confined to the X chromosome, and such a claim would be bizarre and unlikely anyway. They also give a link, though, and it’s the same source used in the television news story.

Here it is: Did you know that intelligence is inherited from mothers? It’s not a study. It’s a blog post. It contains quite a few references to the scientific literature, but it seems to have muddled up their contents quite a bit. None of them say what the author claims.

For instance, the blog post says “Mother’s genes go directly to the cerebral cortex, those of the father to the limbic system” (so that’s where the news got it…), and cites a couple of imprinting studies done in mice. One of them is even titled “Completion of mouse embryogenesis requires both the maternal and paternal genomes.” If you aren’t up on imprinting, it’s the observation that normal development sometimes requires complementary patterns of gene expression on maternal and paternal chromosomes — that is, on the chromosome you got from Dad, gene A might be turned on while gene B is turned off, while on the chromosome you got from Mom, gene A is off and gene B is on, and that complementation means you’ve still got one active copy of each of A and B.

What about the claim that intelligence genes are on the X chromosome? The author cites a 1972 paper that isn’t a study of any kind, but instead merely proposes the hypothesis that “major genes relating to intelligence are located on the X-chromosome”, largely based on the observation that males have a greater frequency of mental retardation and learning disorders than females. The author also cites another paper that was a review of the database of genetic disorders in OMIM that found that 10% of the genes associated with mental disabilities are linked to the X chromosome.

Both of those facts are true: boys are more likely to suffer mental disabilities, and known genes correlated with those problems are found on the X chromosome. This does not, however, imply the existence of “intelligence genes”, nor does it map intelligence to the X chromosome. What it tells you is that boys are hemizygous for the X chromosome, and that recessive alleles that can cause developmental disorders are more likely to be exposed and phenotypically expressed if a) they’re on the X, and b) they are inherited by a boy. Brains are also particularly sensitive to developmental problems, so generic deficiencies are often going to have cognitive consequences.

Another problem is that the OMIM database is not a complete account of every possible gene and its effect. Some genes are easier to isolate phenotypically…like, if you’ve got a lot of individuals running around who are reliably known to be expressing a deleterious allele in the absence of a complementary wild type allele. Like, you know, some boys. The reason the “intelligence genes” are underrepresented in autosomal chromosomes (that is, non-sex-chromosomes) isn’t because they’re not there, but because they aren’t as obviously expressed or as easily detected. What they’re actually reporting is a bias in the literature: the X chromosome, because of its unusual genetic properties, is more brightly “lit up” than the somewhat more difficult autosomes.

So, basically, the article is all wrong, but coming to a simple, sweeping, fallacious conclusion is more attractive to mass media than a complex, multifactorial, correct conclusion. Who knew?

One more thing. You know how they say you shouldn’t read the comments? I read the comments.

They’re a mess. There are lengthy digressions where people pick over the grammar and spelling of the author, who is not a native English speaker, and people who defend it because the content is so interesting (it isn’t. It’s wrong). But it’s still silly, because it’s written in competent if slightly flawed English, and is perfectly clear. It’s just perfectly wrong.

There are lots of anecdotes about smart moms and dumb moms. These are totally irrelevant to the facts, but that actually is kind of interesting, to see how people are really interested in relating science to their personal lives, even when the science is wrong.

But the worst comments, the very worst, are the ones that take issue with the science. Why? Because those commenters don’t understand the science either, and they take an article that has already mangled the information and mutilate it further. The usual suspects, MRA-types, are outraged, because it has a whiff of feminism.

Highly unlikely. IQ is a product of genetic diversity and since XY is by definition more diverse than XX, intelligence is inherited from the contributor of the Y gene. Men outnumber women by a factor of 6:1 at IQs of 140 and above for this reason. Men, on average, are smarter than women because they have a greater diversity of genetic material to draw upon (fewer redundant systems).

If the original article was merely wrong, that comment is stupidity squared. None of that is true. It is factually false and it is built on a collection of presuppositions and theories that are false.

And then there’s this, which starts off well, pointing out that intelligence is complex and not simply reducible to genes, but then it goes off weirdly into Christian gender roles.

IQ is influenced by many factors – perhaps only half of those actually even being genetic. Clearly our Creator designed males and females to inherit particular types of intelligence. Therefore, the X chromosomes provide the feminine aspects and the Y the male characteristics of mental acuity. We are biologically intended to be balanced and complimentary to each other. There is no disputing this obvious fact.

None of that is true, either!

Let us review.

  • Intelligence is not a product of single genes. A gene does not produce intelligence, an array of genes directly affect brain development, even more genes play necessary supporting roles in brain function, and all gene effects are filtered through and regulated by the environment.

  • Intelligence is not a trait localized to the X chromosome. It is a distributed property of many genes on many chromosomes, and of the environment.

  • Masculinity and femininity are cultural properties. They are not genetic. It is a category error to try to find a genetic basis for skirts vs pants, or manly acuity vs feminine submissiveness.

  • Having a Y chromosome does not increase the genetic diversity of your genome (it’s a desert with a paucity of genes!), nor does “genetic diversity” automatically increase your intelligence.

  • Some humans are idiots.

  • Don’t trust TV news or the Huffington Post or random blogs. You should also be critical of papers published in scientific journals.

I despair of humanity sometimes.

This same “study” is also cited in Good Housekeeping. The disease is spreading.

It’s also in the Wall Street Journal, but cites different sources.

Also, AOL.

And Cosmopolitan.

<curls up, dies>


  1. johnson catman says

    Since women carry two X chromosomes — that’s where intelligence genes are located — several studies have found kids are twice as likely to inherit their intelligence from their mom.

    I am not a statistician, but this just sounded wrong from the first reading. I don’t think that is how math works.

  2. qwints says

    This kind of science journalism destroys trust in actual science – nutrition being the classic example.

  3. Larry says

    Male or female, it appears that reporters these days have no X chromosones since it seems they have gotten dumber than ever whether “reporting” on science or politics.

  4. rq says

    Every boy has one X chromosome that they inherited from Mom, and every girl has one X from Mom, and one X from Dad.

    … And since Mom has all the intelligence and Dad has none, this automatically decreases the genetic intelligence of girls, because Dad’s lack of intelligence is bringing them down. Therefore boys are smarter! QED!


  5. Siobhan says

    Man, I’d have a hoot if my blog was cited claiming my original ass-pulled material (which is often explicitly labelled as ass-pulling) was deemed scientifically significant by MSM and turned into a Fractal Wrongness Virus of some kind.

  6. says

    Siobhan: the formula is simple.

    1. Take the “conventional wisdom”.

    2. Invent “facts” to support it.

    3. Reduce it to the most simplistically wrong explanation possible.

    4. Profit!

    I think you’re probably missing the first step, in which you have to pander to what the MSM thinks it already knows.

  7. says

    This is just the perfect confluence of single-study-reporting in the media and online media’s pervasive mistake of clickbait…and it happens with something that’s not even a study. Genius! If it didn’t make me weep a little.

  8. marcoli says

    There is this nerdy joke floating around but I have no idea if it has any basis for truth.
    It says that most of our olfactory receptor genes are on the X chromosome, and that naturally explains why males are more oblivious about odors since they have only one X but females have two.

  9. says

    What the…? Even if the original supposition that “intelligence genes” were located on the X chromosome was true, it wouldn’t make kids twice as likely to inherit their intelligence from their Mom. It would mean that boys would get all of their intelligence from their mothers, while girls got half from their mothers and half from their fathers. And since one of the X chromosomes gets shut down early in development, it would be a coin flip whether it was Mom’s X chromosome or Dad’s that gets expressed throughout the nervous system, including the brain. So yeah, file this one under “fractal wrongness.”

  10. Becca Stareyes says

    I recall seeing this. The source I saw pointed out a correlation between maternal IQ and the child’s IQ. Assuming IQ is telling us more than ‘how someone scores on this one test’, it didn’t bother* to, say, check to make sure this wasn’t a result of biological mothers being the most likely primary caregiver of children**. And the original source might have mentioned that, but the ‘it’s genes!’ is what has been spreading.

    * Or maybe it was ‘hey, someone should follow some of these things up to determine why these correlations exist’: acknowledging that there could be a few different reasons, but they didn’t have the means to test this before submitting the paper.
    ** Which I can imagine checking by looking at adopted children versus non-adopted children, or siblings adopted by different families, or families with stay-at-home dads, gay and lesbian parents, and other situations where the parent who contributed X chromosomes to every kid is not also the primary caregiver. Granted, many of these situations have other confounding factors given how much we default to bio-mom as caregiver, but it’s at least trying to detangle something rather than assuming genetics equals destiny.

  11. frog says

    <blockquoteEvery boy has one X chromosome that they inherited from Mom, and every girl has one X from Mom, and one X from Dad.

    :delicate cough:

    Please do not erase the transfolk, or the folks with very unusual genetic profiles.

  12. says

    to evaluate this claim, the reporter calls up his mom to ask her if he got his brains from her, and then goes to a toddler tumbling class to ask random moms if they agree.

    In other words, the reporter had the necessary time for real fact checking, but just didn’t bother to do so.

  13. Reginald Selkirk says

    … they won’t have an affect on your brain.

    Nothing to see here. Their entire argument is invalidated by a spelling error.

  14. Midwest Humanist says

    Seems to me we need some other kind of term to describe this process. Even the term “junk science,” is misleading in some way as if to say this is somehow just “not very good” science. Besides, often when groups don’t like the results of “science” (think climate change or the effects of tobacco) they scream “junk science!”

    Pseudoscience might be better, in that things like this take some “scientific language” throw it in the blender and spew the results so it looks “sciencey.” But even pseudoscience doesn’t even seem to cover this sort of thing.

    I agree that we have to combat this kind of crap. The commenters here are absolutely right that it is this kind of misreporting that makes “science” seem less real and reliable than it is. I am not sure what that term should be, but we certainly need verbage for “media/pseudoscience hash” like this.

  15. says

    I agree with “Midwest Humanist” that the use of the word “junk science” is a problem. No one in this story has actually done any science, as far as I can tell. It’s terrible science reporting, is what it is, which is also annoying, but a completely different animal from junk science.

    If there were bad science, then the term is “bad science,” meaning people who don’t follow good experimental protocols, who troll the data for patterns instead of designing studies to test hypotheses, or who outright falsify their data.

    Junk science is a political epithet usually used by conservative apologists who don’t want to clean up the water or who deny global climate change is caused by human activity. If you visit the site junkscience.com, run by conservative hack Steve Milloy, you’ll see why I’m saying that.

  16. says

    I would be in favor of a law to require journalists to allow a research paper’s author(s) to add their own words to the end of an article, AFTER reading (not censoring or editing) the journalists words and title first. I don’t see how they could cry censorship over this.

  17. CHARLES says

    Any “science” article pontificating about intelligence, human or otherwise, is meaningless unless the writer explains how intelligence is defined for the purposes of his or her screed. The term intelligence in relation to cognition is as meaningless as soul, spirit, karma or what ever other fuzzy, feel good term the writer chooses to employ.

    Editors should automatically spike such stories

  18. unclefrogy says

    The WSJ now part of News corp.

    I despair sometimes. When asked how you doing I often answer “so far so good” and often add “that’s probably because I do not know what is going on”
    uncle frogy

  19. latveriandiplomat says

    There’s a fair amount of education research showing that the mother’s level of education (not intelligence) correlates strongly with the child’s academic success (again, not intelligence). This is a useful argument for programs to help teen mothers stay in school, for example here:

    IIRC, dad’s education level doesn’t matter nearly as much, but there are all kinds of sociological explanations for that, it doesn’t require X chromosome voodoo.

    At first, I thought that this was what was being misunderstood/misquoted, but it doesn’t appear to be the source.

  20. razzlefrog says

    Sometimes I wish your content weren’t on a platform so explicitly atheistic, PZ. Specifically when you’re doing science in the media analysis as you are here or running swords through quackery. That way I’d feel more comfortable sharing your posts on facebook. I’m 24 years old, a recent college grad, and wary of the possibility that being connected to that kind of thing might hurt me professionally. Especially living in Texas.

    I hope none of what I said in this comment comes off as implying I want you to stop doing godless progressive skewering (honestly, if you stopped doing things the way that you’ve been doing them, I’m not even sure that I’d still come here) I’m just being loud with my disappointment that I can’t easily share what I believe to be a great post.

  21. Algeiban says

    “every girl has one X from Mom, and one X from Dad”

    This is nitpicky, but we women with Turner Syndrome would disagree with your use of “every” here.

    And speaking of women with TS, I guess this bit of nonsense

    “Yes, your dad may give you some intelligence genes, but the study says they won’t have an affect on your brain. The genes will only work if they come from your mom because they will go directly to the cerebral cortex. Genes from the father’s side go to the limbic system”

    means that those of us with classic TS who got the one X we have from our fathers and not our mothers have no intelligence genes that actually work?

  22. says

    EVERY boy gets one X chromosome from their mother, and EVERY girl gets one from both father and mother? I’m pretty sure that human genetics are not always that clean. For example, Klinefelter syndrome, when a person is XXY, and Triple X, where a person is XXX. Not to mention less common variations, such as Turner syndrome and XYY.

  23. says

    Well now, let’s use this as as an opportunity to see if there’s any way to stop this virus from spreading. Some sites moderated and my comments awaiting approval as other’s get posted. Could be interesting,…

  24. slithey tove (twas brillig (stevem)) says

    But the dad’s X came from his mother, so still the X comes from a female, just skipped a generation.
    [refer to color-blindness inheritance]

    Instead of “junk science” I’d like to propose “quasi-science”, (as long as one knows the prefix quasi- means “looks like”)
    Quasar is contraction of quasi-stellar object; looks like a star but clearly is not.

  25. jacquez says

    The thing that kills me is that I would bet money that mothers DO have more effect on intelligence than fathers — not because of the genetic contribution but because of providing the fetal environment. I mean, many things that pregnant people do have effects on fetal development. And yet instead of a perfectly reasonable discussion about that (which let’s all admit would quickly degenerate into yelling about alcohol use in pregnancy), we get this kind of nonsense.

  26. Holms says

    #23, #24
    If a note listing the exceptions has to be placed alongside every descriptor of humans for which there are exceptions, then you are saying every descriptor needs an asterisk. “Boys have an X and a Y chromosome (except for the ones that don’t, for example due to [example]).” “Girls have two X chromosomes (except for the ones that don’t, for example due to [example]).” “The human hand has five digits (except for the ones that don’t, for example due to [example]).”

    This is impressively cumbersome.

  27. What a Maroon, living up to the 'nym says


    It would be enough to change the quantifier. Say “most boys…” or “nearly every girl…”. You end up with a more accurate statement that isn’t any more cumbersome.

  28. Algeiban says

    #28 – I admitted it was nitpicky, but it didn’t sit right with me as someone who the word usage excludes. Seems pretty simple to say *most* boys and *most* girls rather than “every” boy and “every” girl, much less emphasizing the “every” with italics. And no, every descriptor doesn’t need an asterisk, but absolute terms like “every” usually do.

  29. Vivec says

    Definitions almost always break down when you begin to cover the corner cases. That doesn’t therefore justify exclusion, and if anything, is an argument in favor of increased specificity.

    Saying “every” and handwaving away the counterexamples when you mean “most” is just sloppy.

  30. Igneous Rick says


    Not just linguistically, but there are practical reasons to limit the scope of studies and discussions: The more variations you have, the easier it is to go p-fishing. This isn’t to say that those variations aren’t important or are uninteresting, and perhaps their study could yield significant insights on the topic, but using rarer conditions means you will need to rethink your control and experimental groups.

    This is why I stick to rocks.

  31. slithey tove (twas brillig (stevem)) says

    re 27:

    The thing that kills me is that I would bet money that mothers DO have more effect on intelligence than fathers —

    agreed. while embryonic environment provider is also important, the childhood development environment is also quite important. Where women are more commonly the primary provider, while the male is working to pay for sustenance, the mother role is usually fulfilled by women, who stay home and provide essential nurturing. This could possibly [disclaimer] be a testcase of nature-v-nurture. The case discussed in this thread is claiming nature wins, while there seems to be many counterexamples provided here.

  32. Azkyroth, B*Cos[F(u)]==Y says

    Yeesh, this is still around? I remember mom brandishing it at me when I was a teenager. I was skeptical then, figuring it was a sensational overblown response to research finding one or two particular X-chromosome genes that were correlated with cognitive development…

    Is there not even that much basis?

  33. Azkyroth, B*Cos[F(u)]==Y says

    Instead of “junk science” I’d like to propose “quasi-science”, (as long as one knows the prefix quasi- means “looks like”)

    Anything like pseudoscience?

  34. chrislawson says

    I for one am pleased that someone has finally captured the annual migration of the X chromosomes to neo-cortex.

  35. says

    I always wondered why I had to tutor my sister in chemistry and my ex-wife in psychology after they both failed them first time round at uni. Now I know. My mother’s X chromosome smarts weren’t negated by my father’s X chromosome stupidity. That would be a nice theory but good old dad was pretty smart too. Then again so were both of his parents.

  36. Sherry Young says

    My daughter has Turner Syndrome. She got her single x from me. Fortunately, that didn’t prevent her from inheriting my husband’s ability in math because I have very little.

  37. Colin J says

    Of course intelligence comes from the X chromosome. It’s plain logic.

    Generally women have two X chromosomes and men have an X and a Y. Therefore everything we share as human beings, including intelligence, must come from the X chromosome. The Y only provides beards and penises. And deep voices. (And computer game skills?)

    Checkmate sciencists!!

  38. says

    Language pedant time!

    Science is a process and one thing that tends to piss me off that most people ignore is that what we often call science is what goes into and out of that process, not the process itself. We call the input and output of science “science”, I hate that shit but I can only get so far with being annoyed with the definitions of words unless there is an example like this. The people reporting on science are not in any remote sense doing science.

    What we need is language that tightens the contrast between the process of science, and it’s inputs and outputs. Any derogatory terms (and they should be derogatory) should focus on a misuse of those inputs and outputs with respect the process of science and serve to point out the way they screw up the picture of what is really going on.. Do they make sense in terms of an understanding of the knowledge withing a field? Do they display an understanding of precisely what the experiments demonstrated related to the hypotheses tested?

    That’s all I got.

  39. says

    It gets even dafter when you consider nobody actually knows what “intelligence” is, aside from “the thing which is measured by intelligence tests” (yup, that’s right, this whole mess is based around a concept which is circularly defined on its instrument of measure – rather like saying that the quality of “length” is “the thing measured by a ruler”). There are whole chunks of psychological literature attempting to try and nail this particular lump of jelly to the academic wall, but the best definition we have as yet of what “intelligence” might be is “intelligence is the thing measured by intelligence tests”.

    (Which means it’s a combination of problem solving skills, mathematical skills, visual recognition skills, vocabulary skills, language familiarity, and social interaction skills, plus or minus a certain combination of cultural and socio-economic specific factors).

  40. msm16 says

    This trash also has the side effect of perpetuating the myth that “education is for sissies” that seems to have grown up in the last couple of decades. This is an issue where a real men’s rights movement could do some positive good, instead of being a bunch of howling man boobs.

  41. ikanreed says

    The most obvious ad-hoc reason for the proportionally inheritance of maternal intelligence is the reason racehorse breeders look for the maternal grandchildren of champion racehorses, not the paternal children: fetal development is a crucial stage for all mammals, and where hormonal signaling has the greatest impact.

    I’m not trying to make a case for a slightly different biological existentialism here, your mother is no more your destiny than your genes are. But when it comes to nature versus nurture, a huge part of the nurture is how those first few million cells grow and differentiate. Your dad just only contributes the genes to that process, whereas your mom contributes both her genes and her entire body’s effectiveness.

  42. says

    Not quite accurate, but I would say that hormonal signalling in utero would probably be the largest source of information that could result in changes to what we call intelligence (though that is only speculation on my part). However it is not only DNA that is delivered in sperm, it is also many kinds of RNA including not just messenger RNA but other more recently discovered non-coding RNAs like miRNA (also present in the egg). In some cases there is a bit of a “battle” to control the direction of gene transcription after fertilization.