The Real Reason Some People Are Left-Handed Isn't What You Think

Are you left-handed? If so, you are part of a small group of people worldwide. Only approximately 10.6 percent of the population is left-handed, according to Psychology Today, and a study of more than 2.3 million people. If we factor that into the world population of about 7.8 billion people, that means that only approximately 827 million of those people are left-handed. 

While left-handed people are treated well today, it, unfortunately, wasn't always like that. In the past, they were accused of being evil or of being witches. Even the word "left" comes from the Latin word "sinister" (via the Merriam-Webster dictionary). In Latin, sinister means left, but it is now associated with being evil. These accusations are likely because the majority of the population has always been right-handed, so when some people were left-handed, they were treated poorly just because they were different. So, why are some people right-handed and others are left-handed?

Whether someone will be left or right-handed is determined before they are born. According to a 2017 research article published in eLife, it could all begin in the spinal cord where they found the gene activity to be asymmetrical. 

The motor cortex in your brain determines hand and arm movements. 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 thumbs) before their brain can even send signals. 

Researchers decided to study gene expression in the spinal cord from the 8th to the 12th week of pregnancy, and they found distinct differences in the right and left segments of the spinal cord that control leg and arm movement, and this is what could cause someone to be a righty or a lefty. Whether you are left-handed or right-handed, then, is determined way before you were born.