There have been a lot of presumptions on why some people are left handed. Since they only make up 10% of the population, theories have been made to explain their strange group. While people think that it has something to do with the brain, a new study discovered that being a lefthander is an effect of gene activity in the spinal cord during their fetal stage.
According to ultrasound screenings, babies already have the choice on whether to suck their left or right thumb as early as 13 weeks.
A group of researchers from Ruhr University Bochum together with their colleagues from Netherlands and South Africa discovered that gene activity in the spinal cord was asymmetrical in the womb. This made them come up with the theory that this connection is what causes a person to be right- or left-handed.
The team of Sebastian Ocklenburg, Judith Schmitz, and Onur Gunturkun explained that the arm and hand movements start in the motor cortex, the area in the brain which sends a signal to the spinal cord that's translated into a motion. However, they found out that while the right- or left-handedness has already been determined before the fetus reaches15 weeks, the motor cortex and the spinal cord are not yet connected.
This means that the fetus can already move and chooses their favorite hand before the brain starts controlling the body.
For the study, the researchers analyzed the gene expression in the spinal cord from the eighth through the 12th week of pregnancy. Significant differences in the left and right segments of the spinal cord were discovered controlling arm and leg movement.
The researchers concluded that the asymmetrical nature of the spinal cord result in epigenetics, which is how changes in gene expression affect organisms. These changes are influenced by the environment where the baby grows.
Based On Materials From Business Insider