2008 Woodie Awards
Why are only 10 percent of people left-handed?
Faye Flam
Issue date: 11/16/07 Section: Science And Technology
PHILADELPHIA - Plato and Aristotle puzzled over lefthanders, as did Charles Darwin. What determines "handedness"? Why are only 10 percent of us lefthanded, and why did the ratio seem to change over the last century? Are lefties somehow different - less healthy, more creative?
With brain scanning and the latest genetic technology, scientists are finally starting to crack the mysteries. Lefthanders really are special, and the ways they differ are yielding insight into human diversity - especially how one person's brain differs from another's.
Searches for a lefthanded gene, meanwhile, are untangling the roles of nature and nurture in shaping our behavior, and revealing ever more subtle ways that DNA can influence but not determine who we are.
"It's a quirky phenomenon of humans, and people ask why it's relevant," says research geneticist Clyde Francks of Oxford University. "But this is taking us into a fundamental feature of the human brain."
"Lefthandedness is connected to a lot of neurodevelopmental disorders," says Daniel Geschwind, a UCLA expert in what is known as neurobehavioral genetics. People with autism and schizophrenia are more likely to be lefthanded, he says. "But with that risk, there is also gain."
Look at MIT professors or musicians or architects, he suggests, and you'll see a slightly higher percentage of lefthanders than in the general population. Neuroscientists are beginning to figure out why.
The brains of lefthanded people develop more freely in utero, they say, allowing the organization to stray more from the standard design.
In most people, experts say, the left hemisphere of the brain specializes in tasks that are performed in sequence, such as reading and speaking; the right does more holistic processing, like that needed for visual perception. Most people have a dominant left hemisphere, and since each hemisphere controls the opposite side of the body, most of the population is righthanded.
With brain scanning and the latest genetic technology, scientists are finally starting to crack the mysteries. Lefthanders really are special, and the ways they differ are yielding insight into human diversity - especially how one person's brain differs from another's.
Searches for a lefthanded gene, meanwhile, are untangling the roles of nature and nurture in shaping our behavior, and revealing ever more subtle ways that DNA can influence but not determine who we are.
"It's a quirky phenomenon of humans, and people ask why it's relevant," says research geneticist Clyde Francks of Oxford University. "But this is taking us into a fundamental feature of the human brain."
"Lefthandedness is connected to a lot of neurodevelopmental disorders," says Daniel Geschwind, a UCLA expert in what is known as neurobehavioral genetics. People with autism and schizophrenia are more likely to be lefthanded, he says. "But with that risk, there is also gain."
Look at MIT professors or musicians or architects, he suggests, and you'll see a slightly higher percentage of lefthanders than in the general population. Neuroscientists are beginning to figure out why.
The brains of lefthanded people develop more freely in utero, they say, allowing the organization to stray more from the standard design.
In most people, experts say, the left hemisphere of the brain specializes in tasks that are performed in sequence, such as reading and speaking; the right does more holistic processing, like that needed for visual perception. Most people have a dominant left hemisphere, and since each hemisphere controls the opposite side of the body, most of the population is righthanded.
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