"I'm a lefty," Barack Obama joked last month as he signed his first official papers as U.S. President.
"Get used to it."
Good advice, considering that left-handed people don't seem to be going anywhere, despite an array of evolutionary cards—from diseases to elevated risk for accidents—stacked against them.
Now scientists say there may be a slightly sinister secret behind the survival of the left-handed minority: the element of surprise.
Whether during a tennis match or a knife fight, approaching from the left often catches the other 90 percent of humanity off guard, according to a team from the Institute of Evolutionary Sciences at the University of Montpellier, France.
Another key advantage, they say: Left-handed men, on average, have greater earning power than their right-handed counterparts.
(Related: "Gene for Left-Handed Trait Discovered.")
The Case Against Left-Handed Survival
The researchers trawled through previously collected data on left-handedness for their report, which appears in the latest issue of the journal Philosophical Transactions of the Royal Society B.
They found numerous associated evolutionary costs, such as increased risk of schizophrenia, epilepsy, autism, and learning disabilities.
Southpaws—about one in ten people—also face higher rates of serious accidents, probably because our modern, mechanized society is tooled largely for right-handers, the team said.
Male lefties may also be at a reproductive disadvantage, because their on-average shorter stature is less attractive to females, the researchers say.
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