It is a general belief that a person's intelligence is determined by both nature and nurture.

I can find a study by Turner 1996 ( in fact, this is the motivation of this question), which makes the claim that since several genes which determine intelligence appear to be located on the X chromosome, the one men inherit from their mothers, and since a man only has one X chromosome inherited from his mother, so that's why mom's intelligence is very important to her sons, even more so than the father's!

Thus, my question is, do the mother's genes determine the sons' inherited intelligence more than the father's, as claimed by the above paper? In other words, a man inherits less intelligence from his father than from his mother? Note that I don't discount the possibility that the father could have helped to raise his son's intelligence by actively nurturing him in the correct way, just that as far as the "intellect genes" ( if there are such things) are concerned, the father plays less role than the mom.

A similar question is asked at Skeptic.SE, but it is geared more towards the contribution of mom's genes against all factors that account for son's intelligence, nurture and nature. My question is focused exclusively on the contribution of mom's genes vs. dad's.

Any new research on this front?


You might want to take a look on the wikipedia site for x-linked recessive inheritance. The article by Turner mentions that out of 325 known recessively inherited genes associated with mental retardation, 17 are positioned on the x-chromosome. In case you are a male and have one of these seventeen recessive genes on your x-chromosome causing you in some way to be less intelligent, you must have inherited that gene from your mother. In those cases it is more like you inherit "stupidity" genes from your mother, who might be an unaffected carrier of the stupidity gene due to the fact that she has two X-chromosomes and the gene causing mental retardation is only present in one of those x-chromosomes.

There might of course also be recessive genes on the X-chromosome causing males, who has only one X-chromosome, to be smarter but genes that are not causing disease might not be so interesting to investigate from a medical point of view.

According to wikipedia there are 499 x-linked genes and the total number of "vaguely defined traits" are 983.

I would say that yes, as a man you inherit more genes from your mother than from you father affecting your intelligence due to the fact that some genes on your x-chromosome affect your intelligence. Whatever the 499 x-linked genes do, you could say that traits affected by those genes to a greater extent are determined by your mothers genes than by your fathers, if you are a male.

Technically you would of course also have to take the genes on the y-chromosome, which are much fewer, into account.

If we approximate that the human male genome has a total of 20000 protein coding genes, the x-chromosome has 800 protein coding genes and the y-chromosome has 60 protein coding genes a male gets on average (19940/(19940+19200))*100 = approximately 50.945 percent of his protein coding genes from his mother. Now for a highly polygenic trait depending on genes homogenously distributed on all chromosomes one would naively expect that 50.945 percent of the genes contributing to that trait is inherited from his mother.

  • $\begingroup$ Intelligence is a highly polygenic trait and genetic variants affecting intelligence appear to be (very roughly) uniformly distributed over all chromosomes. If intelligence is inherited more from the mother than the father, the actual effect of this difference appears to be negligible. (This is also evident from simple studies that test mother-child and father-child correlations, and they find no difference) $\endgroup$ – Eff Apr 10 at 10:11
  • $\begingroup$ Do genes/genetic variants on the y-chromosome contribute as must to the total variation of intelligence in males as the genes/genetic variants on the x-chromosome even though the y-chromosome is much shorter? You inherit genes you do not inherit "intelligence". $\endgroup$ – Agerhell Apr 10 at 13:52
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    $\begingroup$ No, since the y-chromosome is much smaller, it is expected to contribute less to the variance. But what I'm saying is that the of the total genome, the X-chromosome is only a small fraction of it. Hence, if mothers contribute more to the inheritance of intelligence, then this bigger contribution is at most negligibly larger. We have simple studies that check the correlation of intelligence (or height, or other highly polygenic traits) of father-child and mother-child, and no difference tends to be found. Hence, there can be at most a small difference in contribution. $\endgroup$ – Eff Apr 10 at 13:56
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    $\begingroup$ In Lee et al, 2018 they look at genome association of educational attainment (which is highly correlated genetically with intelligence). In the Manhattan plot you can see a rough "genetic architecture" of the trait in question, and one can see that it is widely distributed over the entire genome. They also analyze the contribution of the X-chromosome. $\endgroup$ – Eff Apr 10 at 14:01
  • $\begingroup$ @Eff, you would like to expand on your comment and make it into an answer? $\endgroup$ – Graviton Apr 12 at 2:12

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