A lot of people believe that kids inherit intelligence from their mothers. Some argue that it is scientifically proven. But what exactly is the actual truth? Read on to know what research has established.
Why do people think we inherit intelligence from mothers?
The factoid that intelligence is passed down only through your mother is aggressively moving across social media users’ trending bars after a September 14th, 2016 article published on a site called “Second Nexus” was reposted by notable accounts on different social media.
The claim has been checked by Snopes and found to be unproven.
As reported by Forbes the Second Nexus article’s main source of information for this “new research” was a woefully unintelligible March 2016 post from “Psychology Spot,” which cited a collection of studies that are decades old. They did not actually cite new research, and they misrepresented the science they used to make their claim, according to Snopes.
Fact: No, Research Has Not Established That You Inherited Your Intelligence From Your Mother.
According to Snopes, these internet claims are based on three main assumptions:
- There are specific and discrete genes that universally determine intelligence.
- Those genes are located on the X chromosome.
- That means that the genes must come from your mother.
Well, it’s all because of the X chromosome. Females have two X chromosomes and Intelligence genes are located on the X chromosomes. Therefore, it is highly likely that children will inherit intelligence from their mothers. But, there is a twist!
Genetics of Intelligence
As per prof David H Skuse, X-linked genes are relatively highly specialized for brain development (but not intelligence) relative to other genes from the rest of the genome, which do not equate to intelligence. And women get one of their two X chromosomes from their father. Despite having two X chromosomes, only one X chromosome is active in each cell of the female.
So, does intelligence come from the mother? Intelligence is inherited from the mother or father?
Tough to say! Isn’t it?
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What researchers say about kids inheriting intelligence from mothers?
Two X chromosomes that a woman carries are not identical. She must have inherited one of them from her mother and the other from her father. When she delivers a child, she passes only one X chromosome to her child after two X chromosomes engage a little genetic swapping themselves. Her child receives the second chromosome from the father.
A mother can pass the X chromosome to both daughter and son, but a father mainly passes the X chromosome to a daughter. Sons get their single X from the mother of course. Since a mother doesn’t carry two identical X chromosomes, they don’t increase the odds of inheriting a specific variant.
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That’s not all. There are many people carrying two X chromosomes (doubled gene dosage), but some people walk around with just one X chromosome. People with doubled gene dosage have most of the one X or the other turned off by each cell.
So, even when a person inherits an X-linked gene variant, it may or may not be used because some cells might just shut it down.
Every person has at least one X chromosome and Mother Nature doles them out to all of us – And you get an X chromosome, and you get an X chromosome! And so do you!
Once you inherit an X chromosome, short of a major deletion, you only receive whatever genes (linked to intelligence or not) are still present on that X chromosome.
A lot of articles on the internet created a big buzz with headlines “we inherit our intelligence from our mothers…” But, the editorial staff of those popular articles is only emphasizing gene variants that might be linked to intelligence and not just genes.
According to researchers, even if a person inherits half of their intelligence from their mother, that proportion is in turn fractured into several genetic variants scattered across our genomes. In short, this whole process of inheriting intelligence is quite complicated.
All these variants function together in different ways to form what we view as intelligence. Also, know that each of these heredity fragments that contribute to intelligence is influenced by a range of environmental factors – both in its immediate molecular world and inputs to the whole organism, that will influence function.
This influence continues after birth as an ongoing mutual interplay of gene variants and environment. It’s like several layers of interacting pieces.
Therefore, you don’t just inherit intelligence from your mother. It’s not just the X chromosome. And it’s also not just about genes.
Inheriting the X chromosome from the mother is just not enough to make you intelligent. Because intelligence is not just about solving complex problems. Rational thinking function is also affected by emotions and intuitions, which are also contributed by fathers. So, dads are equally responsible to bring smarts to the world. Even if a child has a high IQ, it must be nourished throughout life with new challenges. Otherwise, intelligence will disperse.
In earlier research by Africa Check, professor of metabolic medicine Fredrik Karpe told that kids Intelligence is also determined by economic, cultural, and social environmental factors.
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What is all the buzz about conditioned genes and intelligence?
Some online blogs and news stories have also mentioned conditioned genes that are activated only when inherited from the mother and that is vital for embryo development.
According to researchers, “conditioned” genes refer to gene sequences that are tagged as being of maternal origin. However, we also require complementary gene sequences of paternal origin for the entire process to work out.
Some articles that have spread the news that intelligence is inherited from the mother have also highlighted the results (given below) of a 1996 paper to support their claims –
Researchers found that embryos survived when normal embryonic cells were maintained. When they manipulated the rest, they created several genetically modified laboratory mice that did not develop in the same way. Mice that received an extra dose of maternal genes developed larger heads and brains, but smaller bodies. By contrast, mice that received an additional dose of paternal genes had smaller brains, but larger bodies.
But the fact is this experiment involved mouse embryos that were a mix of cells, while some carried double maternal genomes, some carried double paternal genomes. Some parts of the mouse brain that developed carried far more than the other whereas other parts of the brain showed a reverse pattern.
Barry E. Keverne, the senior author of the 1996 paper reported in 2013 that some of the findings may have been the result of a “failure of these (double paternal) cells to thrive and survive when they reach the developing cortex.”
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Is it true that paternal genes are not found in the brain regions responsible for intelligence?
A lot of people in online forums argue that the mother’s genes go directly to the cerebral cortex, while paternal genes go to the limbic system. And the cerebral cortex is the region where humans develop advanced cognitive skills like language, thought, intelligence, creativity like painting.
Well, referring to the 1996 study involving mice, yes it is true double-paternal genes are excluded from the brain regions responsible for intelligence. But, it is also not the right thing to say that our cerebral cortex excises with surgical precision those parts of the cellular genome that are paternally inherited.
Most of the old papers concerning embryo development are 20-30 years old and primarily deal with the discovery that an appropriate embryo development requires both a paternal and a maternal genome and in the absence of these complementary genomes, development fails. Also, when you use your brain you use both cerebral cortex and limbic system functions.
The Bottom Line
There is hardly any new research on the genetics of intelligence or new study published that claims kids inherit intelligence from their mothers. The virality of splashy internet/social media claims “We Inherit Our Intelligence From Our Mothers” or “Kids Get Their Intelligence From Mom” and similar ones grows despite inaccuracies and backup from the latest research. Those catchy and attention-grabbing headlines are the culprit!
These headlines are highly liked, commented on, and shared by – people who think they are geniuses and have mothers to be grateful for and mothers who think their children are geniuses, and some feminists who would love to shout out loud that mothers bring smarts to this world. Such attention-grabbing headlines can help one win a ready-made audience.
Please share this article with anyone who you may think will find it valuable and helpful.
References
Deary, I.J., Johnson, W. and Houlihan, L.M., 2009. Genetic foundations of human intelligence. Human genetics, 126(1), pp.215-232.
Haworth, C.M., Wright, M.J., Luciano, M., Martin, N.G., de Geus, E.J., van Beijsterveldt, C.E., Bartels, M., Posthuma, D., Boomsma, D.I., Davis, O.S. and Kovas, Y., 2010. The heritability of general cognitive ability increases linearly from childhood to young adulthood. Molecular psychiatry, 15(11), pp.1112-1120.
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