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Southpaw Minority

April 15, 2008

A listener asks: Why are so few people left-handed?


Why are lefties in the minority? I’m Bob Hirshon and this is Science Update.

Listener Jessica from Washington, D.C. wrote to ask why only about ten percent of people are left-handed. We asked handedness expert Chris McManus of University College London. He says no one knows for sure, but the stability of that percentage suggests that a gene for left-handedness may be most beneficial in small doses. He compares it to the sickle cell gene: having one copy protects you from malaria, but having two copies, which is much less common, causes sickle cell anemia.

CHRIS MCMANUS (University College London):
And I suspect the same thing is happening with left-handedness. We’re pretty sure there are genes underlying it, and it’s not having two genes for left-handedness that’s necessarily a good thing, it’s probably having one.

But we can’t test that hypothesis until we confirm that there is such a gene, and then figure out what else it controls besides handedness. I’m Bob Hirshon for AAAS, the science society.