Health - Wellness
The Real Reason Some People Are Left-Handed Isn't What
You Think
Whether someone will be left or right-handed is determined before they are born. A 2017 research article published in eLife revealed that it all begins in the spinal cord, much earlier into gestation than you might think.
The motor cortex in your brain determines hand and arm movements, but the research from eLife found that right or left-handedness is determined in utero before 15 weeks gestation and before the spinal cord and the motor cortex are even connected. This means that fetuses choose their right or left hand (for sucking their thumb) before their brain can send signals.
Researchers decided to study gene expression in the spinal cord from the 8th to the 12th week of pregnancy, and found differences in the right and left segments of the spinal cord. These segments control leg and arm movement, and this is what could cause someone to be a righty or a lefty.