A blog post written by a Spanish psychologist has recently been taken over by some French media. He says the intelligence is mainly transmitted by the mother. Yet it is false.
By Gary Dagorn
She summarizes the results of several scientific studies affirm that intelligence is mostly genetically transmitted by the mother. The reasoning is the following: the genes of intelligence is mainly transmitted through sexual X chromosome, women have two X chromosomes, she is responsible for the transmission of cognitive abilities in children
Takeover by number of enthusiastic media, information was widely shared and processed by them simplistically or completely wrong.
- What is intelligence?
There is no single definition of what intelligence is or how the measure . In biology the term often refers to general cognitive abilities of be human, that is to say the memory, attention, language, reasoning ability and all executive functions play a role in the processing of information by our brain .
Continuous technological advances allow for thirty years studies finer human genome, so identify the role and functions played by genes. Those responsible for the effectiveness of our cognitive abilities, commonly called the “intelligence genes” are the subject of special attention and much research in genetics.
The did we find? It would seem so, but the case is much more complicated and nuanced than it appears.
- The X chromosome is it bearer of these “intelligence genes”?
This is the assertion Jennifer Delgado, relaying several scientific studies on the subject. But the conclusions of these studies were invalidated since by new research. This is not unusual because genetic research is expanding.
The article is based particularly on a 1972 study by Robert Lehrke which was the first to make a link between the X chromosome and cognitive abilities. But the study involved a small sample (ten families) and made the observation that mental disorders involved more men than women. Lehrke then concluded that genes that affect intelligence were on the X chromosome
Several studies have subsequently demonstrated that several genes responsible for mental disorders were located on the X chromosome, reinforcing the thesis Lehrke. But as genetic research have made progress in identifying genes and their functions, it appeared that it was not so simple.
Three key findings emerged. The first is that genetic inheritance plays a less important role in determining cognitive abilities than previously thought. Estimated 70% to 75% there yet thirty, the role of genetics is today estimated at approximately 20% to 40%. Second, several recently published studies show that there is no significant correlation between “intelligence genes” identified and IQ.
Finally, if these genes exist, they are far more numerous than previously thought, and thus play a low individual role. The study in 2013 DNA and IQ of almost 18 000 children coming from Australia of Netherlands and UK already showed that our cognitive abilities depend on a large number of genes. But one of the most comprehensive studies on the subject was published in the journal Nature Neuroscience in December 2015. This study shows that cognitive abilities are influenced by two large networks Genoa. on the 1225 M1 network and 4 of the M3 network 160, or 5% of the total.
The researchers especially emphasize the low individual influence of genes. “The traits such as intelligence are influenced by a large group of genes working in concert as a team of Football comprised of players positioned differently” said Dr. Michael Johnson the main author of the study.
It is true that the X chromosome contains genes that influence our cognitive abilities where the small Y chromosome (which contains only a hundred genes) contains none. But it is wrong to conclude that the mother transmits the intelligence, the weight of the X chromosome was relatively low.
This can however explain some differences between the sexes, such as higher incidence of mental disorders in men. A child receives an X chromosome from his mother and a Y chromosome from his father, where a child receives an X chromosome from each parent. If the genome of the parent contains an allele can cause mental disorders, his son will have a higher probability of receive allele in question in relation to a daughter, who also receives one X chromosome from his father (one of the two X chromosomes at random, is then inactivated, inhibiting the expression of its genes).
- The transmission of “intelligence” is it solely genetic?
Absolutely not. Although researchers do not agree on the exact part of the role of genetic transmission, they agree say as many other factors have an influence on the effectiveness of our cognitive abilities as the environment or education. This is a point that is also found in the blog post by Jennifer Delgado, but is reduced or absent treatment that made the French media.
The education and the environment social and cultural are also determining influence genetics in development intellectual of a child. A study published in 1994 covering children from three to six years stressed that the IQ of children studied was lower when they suffer from problems of nutrition or do not benefit non-formal education.
In Zhao Bowen, director of the Cognitive Genomics Laboratory Beijing Genomics Institute, was quoted as Global Times “We need know that within that we have inherited, there are factors over which we have no influence and others that can be change . And we are trying to do good use of them by cultivating our potential in an optimal environment. “