A post from the site Second Nexus has recently gone viral in mine (and I assume other people’s) Facebook feeds, shouting a interesting claim that ‘New Research Has Established That Intelligence Is Inherited By The Mother’. The piece is bylined ‘Editorial Staff’ and gives no mention of a name, which is also true for a considerable number of other articles on the site, presumably because one person was too embarrassed to claim it as their own. Let me just start off by saying there is so much wrong with this article – hopefully I can explain some of that here.
The premise of the article seems to be that children inherit intelligence from their mothers as the genes linked to intelligence are ‘located on the X chromosome and mothers have two’. Well this is true, as most women have two X chromosomes – but these aren’t carbon copies of each other and every woman will inherit one of those X chromosomes from her father.
A mother’s two X chromosomes will undergo some swapping of genetic material as one is passed on to the child, before those children receive their second chromosome (whether that’s another X for a female or Y for a male) from their fathers. This way, female children receive genetic material in the form of their X chromosomes from both parents, but the two X chromosomes her mother has aren’t the same and doesn’t double the chances of inheriting a certain gene or gene variant (a slightly different type of the same gene).
To make things even more complex, some individuals walk around functioning just fine with just one X chromosome whereas some have two. However, for people who have two (or even more) X chromosomes, our cells can ‘switch off’ genes from the other chromosomes to control their expression – so even having these genes doesn’t guarantee they will be used. Everyone has at least one X chromosome – yes, even males.
Let’s get this out of the way: intelligence is super complicated; about half of the factors that influence our intelligence can be linked to our genome (and therefore inherited), but they are spread across a vast plethora of genes, further scattered into many gene variants. These variants interact with each other and different, completely unrelated genes to influence intelligence as we measure it. To throw another spanner into the works, the inheritance of those genes is influenced by many different environmental factors that influence how they will work both in the cell and the whole organism. This environmental influence interplays until our deaths, creating lots of interacting pieces in the way our genes are expressed. So no. Intelligence isn’t just from your mother. It isn’t just from your X chromosome. It isn’t even just your genes.
The article then quotes research from 1994 – correct me if I’m wrong, but unless I’ve been living in a time-warped alternate reality, I’m not really 22 years old and research from 1994 is totally ‘new’. In fact, none of the references sources are ‘new’ – there’s no research from after 2012, let alone anything published this year. After discussing maternal and child interactions post-birth for a distracting while, it wheels back to say:
‘Researchers discovered that there are conditioned genes which only activate when inherited from the mother and that are crucial to the proper development of the embryo.’
I don’t know if these genes have been using Head & Shoulders, but I’m not sure what they mean by ‘conditioned’ gene – perhaps that they can be traced back to being of maternal origin. The thing is though, we need copies of those genes from our fathers for this whole make-a-baby thing to work out as well. They then continue by stating:
‘Scientists hypothesised that genes essential to the development of the embryo would also have a significant impact brain function in the lives of animals and people.’
You don’t even have to have a biology degree to realise any gene important for embryonic development would clearly affect brain development. What it says on the tin, people.
It only gets worse, I’m afraid:
‘Researchers have not found paternal genes in the cerebral cortex, where humans develop advanced cognitive functions such as intelligence, thought, language, and painting.’
This is actually in reference to an unrelated paper published in 1996 where researchers used a mix of cells and monitored the development of mouse embryos, some carrying double paternal genomes and some carrying double maternal genomes. Some parts of the mouse brain that developed carried far more of one than the other whereas other parts of the brain showed a reverse pattern – but the researcher said himself that these findings could be because cells just couldn’t survive or develop correctly when they didn’t have both maternal and paternal genes. So what they’re referring to is that double-paternal cells from the study tended to not appear in the cerebral cortex, but it also gives the false impression that this area of our brains somehow surgically removes parts of the genome that are inherited from our fathers. And then there’s the ‘advanced cognitive functions’ such as painting…? What?
The article itself seems to have stemmed from a blog at a site called Psychology Spot, which itself is full of incorrect information about genetics and embryonic development, with 14 out-of-date references with most not even referring to intelligence. They mostly refer to the discovery that an embryo needs both paternal and maternal genes for proper development.
The second source for the claim is from… Cosmopolitan magazine. I think that’s pretty self-explanatory.
So despite the bad science, why did this post get so viral? Perhaps it’s the humblebragging of mothers who want to feel like they and their children are geniuses or you’re a feminist and want to claim the female race are bringing the brains to the world. Pretty sold audience to share your material. Despite the claims and the articles that follow being full of rubbish, confirmation bias is a powerful thing – enough to make us click and share, without considering the information presented to us.