Scientists at the Ruhr University in Bochum, Germany, have discovered that the brain has nothing to do with this preference
It is estimated that approximately 12% of Spaniards are left-handed, which would correspond to more than 5 million inhabitants. Our country is not an exception, and that is that left-handed people are around 10% of the world population.
These people have suffered rejection and stigmatization throughout History. The word dexterous in one of its meanings means, according to the Royal Spanish Academy, "skillful, expert in an art or trade". Sinister, on the other hand, has very negative connotations, such as "naughty and malicious, unhappy, unfortunate or ill-fated".
Many have been the assumptions that have wanted to demonstrate why some people are left-handed and others are right-handed. The theory that has gained most strength in all these years explains that this quality is the result of the asymmetric activity of the brain during the fetal stage. Now, thanks to an investigation of the Ruhr University of Bochum, in Germany, we can know the truth.
This analysis, carried out by Sebastian Ocklenburg, Judith Schmitz and Onur Güntürkün, has been recently published in Life magazine, where we have been able to know that being left-handed or right-handed is determined since we are fetuses, although the brain has little or nothing He has to see about it. This preference is given from the eighth week of pregnancy and we already act as such within the maternal belly. Five weeks later, the fetuses already suck their fingers, choosing the right or the left depending on whether they are left-handed or right-handed.
The key is to understand how we move. The motor cortex sends a message with the orders to the spinal cord so that it executes the movement in any extremity. The fetuses, as the study has discovered, still have not communicated both parts of the body. Therefore, the decision to use one limb or another is exclusive to the marrow.
In addition, continuing with the research, scientists have determined that the fact of using more one hand or another does not depend on our DNA but on environmental factors. During pregnancy, these influences can affect more or less one part of the spinal cord or another, causing us to stimulate more the left area (then we will be left-handed) or right (or right-handed).
