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.
<curls up, dies>