The study of intelligence is something that fascinates researchers and parents alike. As we focus more and more on education and learning to advance in our careers, parents want to know how to maximize their child’s chances for a strong intellect. Unsurprisingly, a good portion of our intellect is genetic, passed down from our mothers and fathers. But does one parent’s intelligence influence a child more than the other’s? New research suggests that it might.
Passing Down Intelligence
Researchers have found that our intelligence levels may be passed down from our mothers instead of from each parent equally. If this is true, it could have a huge impact on how people pick partners, the role of each parent in a child’s life, and other important life decisions. These findings would be a major breakthrough when it comes to studying the origin of intelligence.
Some research has suggested that there is a discrete “intelligence gene” that exists in the X chromosome. Since women carry two X chromosomes, the researchers suggest that most of our intelligence comes from our mothers.
But these findings are still in the nascent stages and not much is definitive. For example, one 2010 study published in the journal “Molecular Psychiatry” attempted to figure out just how large of a role genetics plays in our overall intelligence. That study was a meta-analysis of studies of fraternal twins. It found that these studies “yield heritability estimates of about 50%, indicating that about half of the total variance in g (the intelligence gene) can be accounted for by genetic differences between individuals.”
In other words, about half of what makes up our intelligence comes from our parents.
One issue with this study is that other researchers have not been able to replicate it, which casts some doubt on the methods of these researchers. Study validity requires that other researchers should be able to use the same conditions and get approximately the same results. That has not happened thus far, calling into question the validity and reliability of this study.
If this study isn’t reliable, that also leaves us without a definitive answer on just how much of our intelligence is genetic. That genetic theory of intelligence also relies on some interesting, albeit unproven, theories. One theory is that because there is less variation in the intelligence of women, intelligence must be carried in the X chromosome. This was a theory published in 2009 in the journal “Perspectives in Psychological Science.”
In that journal, the researchers postulated that the relative uniformity in female intelligence was due to the fact that defective alleles in the X chromosome could be offset by the other X chromosome because women are heterozygous (carrying two different alleles). In men, if there’s a defective allele in the X chromosome, it will be carried to every cell in the body.
While this is an interesting theory, it doesn’t necessarily match the facts. That’s because not every X chromosome in the body is the same. In other words, a man may have one defective X chromosome in one part of the body that is not the same throughout the body. Because every pair of chromosomes is unique, it doesn’t necessarily follow that intelligence is passed on by the X chromosome.
While this theory hasn’t been definitively proven, there are still many theorists who do believe that the X chromosome is the center of intelligence in the body. If that is true, then it follows that all men receive their intelligence from their mothers. That’s because all women pass an X chromosome to their offspring. Whether the man passes an X chromosome or a Y chromosome determines the sex of the baby. If the X chromosome is where intelligence lies, then all men get intelligence from their mothers, whereas women get intelligence from both the mother and the father.
These theories are interesting, but they are all far from proven. While most researchers do agree that there is a genetic component to intelligence, just how that intelligence is passed on to offspring is still being debated. There are also theorists who would argue that when it comes to intelligence, nurture has more to do with it than nature. So although there are some who suggest that intelligence is passed down directly from the mother, the truth isn’t that simple. But it’s certainly true that having an intelligent mother gives a child a better chance of being intelligent. If you think you’re a smart person, thank your mother just to be safe.