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Is Intelligence Really Inherited from Mothers?

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Genetic science is getting exciting. Everything you’ve read about in science fiction books is happening. From test-tube babies who never see the inside of a natural uterus to genetic manipulation ridding new babies of the genetic potential for negative attributes, everybody wants to know how all this is going to affect our everyday lives.

As scientists unlock the secrets of human genes, they’re beginning to understand how those strings of DNA turn us into the people we are.

What does this mean?

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Scientists are beginning to be able to isolate the origin of certain genetic traits. For example, science now postulates that general intelligence comes from the X chromosome. Women typically have two X chromosomes, while men only have one. Therefore, in male babies who only get a single X chromosome from their mothers, it definitely comes from the mother. Female babies, however, do get an X chromosome from their fathers.

It gets more complicated than that, though. Even if it’s possible for an X chromosome wielding intelligence to come from the father, some genes are hypothesized to be “conditional,” meaning they are only expressed if they come from a specific parent. Therefore, if the X chromosome comes from the father, that intelligence gene is overridden by the same gene that the mother’s DNA carries.

Is all of this true?

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Maybe.

Simply put, we don’t know enough about genetics to make such a claim confidently. However, the idea hasn’t been completely disproven. It’s complicated.

First of all, it’s important to note that genetics are never as cut-and-dry as they seem. Genetics are less of a map of a person’s future and more a log of their potential. A person, for example, may have the genetic potential to grow to be 6’7”, but if she doesn’t get sufficient nutrition during her growing years, she most likely won’t reach that height. This is the old “Nature vs. Nurture” argument.

Science also postulates that only 60% of intelligence comes from genetics at all, and the other 40% is determined by the conditions of the person’s life. This is why the children of older parents are statistically smarter than children of younger parents. When people have the money, experience, and patience that typically comes with age, they can invest more of their time, money, and resources into the rearing of their children, thereby bringing out the best of their genetic potential.

In addition, there are multiple genes that play into a person’s intelligence. Some of these genes have been mapped while others have not. Some of them are conditioned to come from the father as well as others conditioned to come from the mother.

Saying genes are “conditional” is a bit of an oversimplification, as well. It turns out genes can be switched on and off multiple times throughout a person’s life. Epigenetic tags are bits of protein that attach to the DNA to change their expression. One way this famously plays out is in obesity genetics. Children born to obese parents are more likely to be obese later in life than children born to people who were born to parents who had previously been obese, but were not during the time of conception and pregnancy. The obesity gene gets tagged by one of these proteins, and those tags are sometimes passed on to children’s DNA.

In terms of intelligence, then, it’s really up to the entire life experience of the mother, father, and offspring.

Sorry, women. It’s still important to find an intelligent father for your progeny.