Why am I right-handed, but my brother is left-handed?
We searched on “cause of left-handedness” and thumbed through the sites in Yahoo!’s Left-Handers category. We turned up plenty of opinions, but no definitive answer to your question. According to Scientific American’s Ask the Experts feature, scientists have been studying “handedness” (i.e., which hand people tend to use for writing and other precise motor skills) for about 160 years, and they still haven’t discovered what causes someone to prefer one hand over the other. Most people in the world are right-handed — only 5% to 30% are left-handed. No one’s sure if left-handedness is genetic, a learned behavior, caused by prenatal or birth trauma, or if it’s some combination of these factors. Studies of <
