21 December, 2014
Roughly ten percent of the human population is left-handed. There are twice as many lefty males as females. A study of ultrasound pictures of 270 fetuses in the womb showed that about 9 out of 10 sucked their right thumb while in the womb.
Prejudices against left-handers have been around all throughout history, lefties were said to be inferior. Left-handed people were declared to be servants of the Devil by the Catholic Church. For awhile, left-handed students who attended Catholic schools were forced to become right-handed. The wedding ring is actually placed on the left hand to chase away evil spirits that may haunt the marriage. Nations in the Middle East the right hand is used to touch parts of the body above the waist, while the left hand is used for below the waist.
Scientists have been searching for the answer as to why the majority of people choose the right hand, and why choosing the left hand in such a minority. Handedness is not set at birth. It develops, and can be influenced by outside conditions. Some hypothesize that there may be a genetic cause to handedness; handedness can be subject to change due to the environment.
Many scientists believe that handedness is genetic. This theory would suggest that left-handedness is a recessive gene, and right-handedness would be a dominant gene. This may explain how left-handedness occurs more often in a family that has a background of left-handedness. A study done shows that the chance for two right-handed parents having a left-handed child is 2%. One parent left-handed and the other right-handed makes it a 17% chance, and two left-handed parents having a lefty is 46%.
The human brain is divided into two hemispheres, the left and right hemispheres. The two hemispheres have connections that pass information between the two. The brain has great importance to hand preference. The right half of the brain is the center where the visual, spatial and...