There's a minority that not many people think about that has stumped scientists for decades: lefties.
About 10% of the human population is left-handed, yet no one knows for sure why lefties are so rare.
It's probably the result of a mix of factors, including things related to genetics, evolution, and even prenatal hormones. Or it could be the result of something else.
Here are some of the most interesting facts researchers have reported as they attempt to unlock the keys to left-handedness:
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Twins are more likely to be left-handed, but no one knows why.
Source: Behavior Genetics, 1996
Two left-handed parents have a 26.1% chance of having a left-handed child, whereas two right-handed parents only have a 9.5% chance.
Source: Handbook of Neuropsychology, 1992
Most animals show no preference for handedness, or when one hand is more dominant than the other. Humans and our closest relatives, chimps, are an exception. About 90% of humans and 70% of chimps are right-handed.
Source: Monitor on Psychology, 2009
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