Why Are Some People Left-Handed?
Mar 16, 2018 06:00 AM By Sadhana Bharanidharan
Is the brain responsible for determining our preferred hand in activities like writing and eating? The answer may come as a surprise.
Over the years, there have been several theories to understand "handedness" or why people develop a more efficient preference for either one of their hands, and in exceptionally rare instances, both of their hands. Ultrasound scans in the 1980s first showed that a preference of moving the left or the right hand develops in the womb as early as the eighth week of pregnancy. The sucking of the left or right thumb starts from the thirteenth week.
http://www.medicaldaily.com/why-are-some-people-left-handed-423114
