New research may show that we get our intelligence from our mothers, and not from our fathers.
We already knew that because intelligence as a trait is carried by the X chromosome we were more likely to get it from our mothers (as women carry two X chromosomes, compared to men’s one), but now geneticists are saying intelligence is carried via what are known as conditioned genes.
Conditioned genes work conditionally. That is, sometimes they come from the mother, and sometimes they come from the father, but in the other instances, they are transmitted as deactivated genes.
Geneticists now say that the conditioned genes for advanced cognitive function may be naturally deactivated when passed on from our father, meaning the intelligence we get in our genes is coming solely from our mother.
As a result, intelligence is believed to be a conditioned gene we get from our mothers.
In one study of mice, for instance, researchers found genetically modified mice who were given extra maternal genes developed larger brains and heads, but had smaller bodies; mice who were given extra paternal genes, conversely, had smaller brains and heads, but larger bodies.
More than that, the researchers found cells with paternal genes congregated in the limbic system, responsible for aggression, food, and sex drives. Conversely, they didn’t find any of those paternal cells in the cerebral cortex, which is responsible for thought, language, planning, and reasoning skills.
And those findings translate to humans as well.
A research team in Glasgow tested how intelligence and genes are related. In a study of nearly 13,000 people between the ages of 14 and 22, they found that even after accounting for other factors (such as education and socioeconomic status), the best predictor for intelligence was the mother’s IQ.
That said, they and other researchers also caution that native intelligence via genetics is not the only factor in how intelligent we become. In fact, geneticists generally agree that only 40-60 percent is hereditary, meaning an equal portion of our intelligence comes from our experiences and the environment in which we grow.
Of course, our mothers are significant there as well, as multiple studies suggest that the bond between a child and their mother is a significant predictor of future happiness and intelligence as well.
For instance, a research team at the University of Washington found the strength of emotional bonds between a child and mother may help determine growth in some regions of the brain; in a seven-year study, the team found children supported emotionally displayed significantly larger hippocampi by age 13. This is important, because the hippocampus is the region of the brain responsible for learning, memory, and stress responses.
Additionally, social psychologists point at the bond between mother and child as important and necessary for developing problem-solving skills and confidence as a child develops.
Of course, that isn’t to say strong fathers can’t fulfill some of the same roles. Clearly, they can. And other researchers have also pointed out that conditional genes from our fathers may help unlock other traits (such as intuition and emotional intelligence) than can help us make the most of any intelligence we get from our mothers.