Why are we right or left

The tendency to move more than one hand appears in intrauterine life around the eighth week of pregnancy, according to recent findings with ultrasound imaging.

Previously, scientists considered that there was a difference between the left and right legs in the activity of the genes of the two hemispheres of the brain.

Recently, researchers at Ruhr-Universitat Bochum, who analyzed the genes in the spinal cord during the weeks of the eighth and twelfth pregnancies, came to the conclusion that the origin of one of the hands is in the spinal cord.

The movements of the arm and hand start from the motor cortex in the brain, which sends signals to the spinal cord. This command turns into motion. The motor cortex is not connected with the spinal cord from the beginning, and the "choice" of one of the hands appears before these connections are formed. This is why researchers believe that the use of the right or left hand is decided on the spine.

Thus, researchers have found differences between the left and right segments of the spinal cord's spinal cord from the eighth week of intrauterine life, and these differences control the movements of the hands and feet.