Q: Did you see intelligence is inherited just from mothers?
A: Yeah, nah.
Q: No, seriously. It’s in Stuff. “Recent scientific research suggests that rather than intelligence being genetically inherited from both their parents, it comes from their mother.”
A: I don’t think so.
Q: You’re objecting to their definition of intelligence, aren’t you?
A: Not this time. For today, I’m happy to stipulate to whatever their definition is.
Q: But they have Science! The “intelligence genes originate from the X chromosome” and “Some of these affected genes work only if they come from the mother. If that same gene is inherited from the father, it is deactivated.”
A: That sounds like two different explanations grafted together.
A: Some genes are imprinted so the paternal and maternal copies work differently, but that’s got nothing to do with the X chromosome.
Q: Why not?
A: Because any given cell has only one functioning X chromosome: for men, it comes from your mother, for women, it’s a random choice between the ones from each parent.
Q: Ok. But are all the intelligence genes on the X chromosome?
A: No. In fact, modern studies using hundreds of thousands of genetic variants suggest that genes contributing to intelligence are everywhere on the genome.
Q: But what about the ‘recent research’?
A: What recent research? I don’t see any links
Q: Maybe they’re in the blog post that the story mentions but doesn’t link to. Can you find it?
Q: And the references?
A: Mostly in mice.
Q: But there’s one about a study in Glasgow, Scotland. In nearly 13,000 people.
A: There is, though it’s actually an analysis of the US National Longitudinal Study of Youth. Which, strangely enough, did not recruit from Glasgow, Scotland. And less than half of the 12,686 participants ended up in the analysis.
Q: Whatever. It’s still recent research?
A: Ish. 2006.
Q: And it found mother’s intelligence was the most important predictor of child’s intelligence, though?
A: Yes, of the ones they looked at.
Q: So, more important than father’s intelligence?
A: That wasn’t one of the ones they looked at.
Q: “Wasn’t one of the ones they looked at”
Q: Ok. So is there any reason for saying intelligence genes are on the X chromosome or is it all bollocks?
A: Especially before modern genomics, it was much easier to find out about the effects of genes on the X chromosome, since breaking them will often cause fairly dramatic disorders in male children.
Q: So it’s not that more intelligence-related genes are on the X chromosome, just that we know more about them?
A: That could easily be the case. And just because a gene affects intelligence when it’s broken doesn’t necessarily mean small variations it in affect normal intelligence.
Q: But wouldn’t be it great if we could show those pretentious ‘genius’ sperm-donor organisations were all useless wankers?
A: On the other hand, we don’t need more reasons to blame mothers for their kids’ health and wellbeing.