Smart people should thank their mothers because, according to researchers, their mothers are the principal responsible for transmitting the intelligence genes. Thus, gender stereotypes that survived over centuries are perhaps about to disappear. Single women who want an intelligent son don’t need to look for a Nobel Prize at the nearest sperm bank and it is likely that men begin to re-evaluate the intelligence of women.
At the basis of this idea there are those known as “conditioned genes”, that behave differently depending on their origin. Basically, these genes have a kind of biochemical tag which allows to trace the origin and reveals even if they are active or not within the progeny cells. Interestingly, 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. Obviously, other genes work the opposite, are activated only if they come from the father.
Mother’s genes go directly to the cerebral cortex, those of the father to the limbic system
We know that intelligence has an hereditary component, but until few years ago we thought that much of it depended on the father as well as on the mother. However, several studies revealed that children are more likely to inherit intelligence from the mother, because intelligence genes are located on chromosome X.
One of the first studies in this area was conducted in 1984 at the University of Cambridge, to this research followed many others over the years. In these studies was analyzed the co-evolution of the brain and the conditioning of the genome, to conclude that the maternal genes contribute most to the development of the thought centers in the brain.
During the first experiment, researchers created the embryos of special rats that only have genes of the mother or the father. But when came the time to transfer them to the uterus of an adult rat, the embryos died. So it was discovered that there are conditioned genes which are activated only when inherited from the mother and that are vital to the proper development of the embryo. On the contrary, the genetic heritage of the father is essential for the growth of the tissue that will form the placenta.
At that time, the researchers hypothesized that if these genes were important for the development of the embryo, it was also likely that they could play a major role in lives of animals and people, maybe they could even result in some brain functions. The problem was how to prove this idea, because embryos with genes from only one parent died quickly.
The researchers found a solution: they discovered that embryos could survive if normal embryonic cells were maintained and the rest were manipulated. This way they created several genetically modified laboratory mice that, surprisingly, did not develop the same way.
Those with an extra dose of maternal genes developed a bigger head and brain, but had little bodies. Conversely, those with an extra dose of paternal genes had small brains and larger bodies.
Deeply analyzing these differences the researchers identified cells that contained only maternal or paternal genes in six different parts of the brain that control different cognitive functions, from eating habits to memory.
In practice, during the first days of the embryo development, any cell can appear anywhere in the brain, but to the extent that the embryos mature and grow, cells that had the paternal genes accumulate in some areas of the emotional brain: hypothalamus, amygdala, the preoptic area and the septum. These areas are part of the limbic system, which is responsible for ensuring our survival and is involved in functions such as sex, food and aggression. However, researchers have not found any paternal cells in the cerebral cortex, which is where they develop the most advanced cognitive functions, such as intelligence, thought, language and planning.