The idea that intelligence is inherited only from the mother has been going viral for a while and it all started with a blog post published on Psychology Spot.
The problem with this blog post is that it doesn’t just make wrong claims about genetics and intelligence, but it also cites outdated research papers and misinterprets their findings.
According to the blog’s author, brainy people should thank their moms for their high IQ test scores. Apparently, intelligence genes are “conditioned genes” that are activated only if inherited from the mother.
Unfortunately, things are not that black and white when it comes to genetics, so let’s take a closer look at what science actually says about the way we inherit intelligence.
Intelligence genes
The original blog post explains that mothers pass on intelligence because intelligence genes are located on the X chromosome. This may sound plausible – but only if you know nothing at all about genetics.
It’s true that women have XX chromosomes, but they only pass one of those chromosomes to the child. As you’ll remember from your high school biology classes, fathers have XY chromosomes. This means that if the child happens to be a biological female, the father passed his copy of the X chromosome.
In other words, even if the theory about mothers passing on intelligence was true, it would only explain the heritability of intelligence in boys, not girls.
Another reason why the theory fails is the simple fact that scientists have never identified a single gene responsible for intelligence. In fact, intelligence has been linked to more than 500 genes.
We still haven’t figured out an accurate way to measure intelligence let alone discovered the exact genetic mechanism behind its heritability. What we do know, however, is that genes are just part of the equation.
Intelligence and environment
Intelligence is the result of an extremely complicated interplay of genetics and the environment. It’s quite telling that the blog post on Psychology Spot never mentions the role environmental factors play in determining someone’s intelligence.
A number of environmental influences are known to affect the development of intelligence. Just some of these influences include prenatal and early nutrition, maternal socioeconomic class, educational opportunities, parental encouragement, and sibling interaction.
In fact, studies have shown that environmental enrichment can raise general intelligence in children. While these effects usually fade out once the child is removed from an intellectually-stimulating environment, these findings still provide compelling evidence that human intelligence is malleable.
The verdict?
So, where exactly does our intelligence come from? In short, we don’t know. There are a number of factors – both genetic and environmental – that underlie human intelligence.
Even if we really did inherit “intelligence genes” from our mothers, this still wouldn’t account for the complex interaction between genes and the environment that forms the basis of intelligence.
Genes are not the be-all and end-all of intelligence and there is a vast area of research yet to be explored about what makes one person smarter than the other.
Sources:
https://www.verywellmind.com/what-factors-determine-intelligence-2795285
https://ghr.nlm.nih.gov/primer/traits/intelligence
https://www.sciencedirect.com/science/article/pii/S0960982213008440
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