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The Truth about Left-Handed People　　About 90% of people in the world today are right-handed.The other 10% are left-handed, including Obama, the President of the US.Every day, left-handed folks quietly face problems.It could be something as simple as driving a car or using a can opener.
Why are so few of us left-handed? One theory is that handedness (hand preference) could be a result of genetics.Scientists say that there are two genes (基因) associated with handedness.One is the D gene.It is more frequent in the population and promotes (促成) right-hand preference.The other is the C gene.It has the ability to promote a preference for either hand.When the C gene is present, there is a 50% chance that a person could be right- or left-handed.
Another theory has to do with human brains, which are made up of two halves.If the left half is more powerful, then one is most likely right-handed.But with left-handers, it is more complicated.Seventy percent of them are also left-brain dominant (占优势的).The other 30% have right-side dominant brains.
During the 18th and 19th centuries, left-handedness was considered a disability.But not all of the myths about left-handers are bad.One myth suggests that they are more creative and smarter than the right-handers.So far scientific research has yet to find any divuth to these claims.In fact, a 2013 survey out of New Zealand found that left-handers and right-handers were the same.
Life might be a little more complicated for left-handers when it comes to cutting a piece of paper or opening a bottle of wine.However, it seems to be a good sign if you are divying to make it to the White House.In the 19th century, left-handedness was no longer considered abnormal.