Air Date: Week of December 17, 2004

Living on Earth’s Jenn Goodman reports on a study that finds being a lefty may have its fighting advantages.

Transcript

CURWOOD: Just ahead: getting ready to celebrate the holidays. But first, this Note on Emerging Science from Jenn Goodman.

[SCIENCE NOTE THEME]

GOODMAN: In what you might call revenge of the southpaws, researchers have discovered that lefties hold a decided advantage in both fighting and close contact sports—and this edge may explain why left-handedness has survived natural selection.

If nature had its way we’d all be right-handed, but between 10 to 15 percent of the world’s population are southpaws. The reason? Developmental experts believe that left-handedness is caused by stress to the fetus, either during early developmental stages or during birth. The stress diverts the nervous system from its typical right-handed path. And because developmental stress also correlates to such conditions as low birth weight and reduced life span, it might be expected that the left-handed trait would eventually be selected out.

But, researchers have discovered just the opposite. They’ve found that left-handers are thriving, particularly in the most violent societies. In a study in the current issue of the Proceedings of the Royal Society, researchers looked at tribes in eight traditional societies and compared the frequency of left-handed people in the population with their societies’ murder rates. They discovered that the most peaceful societies had the lowest percentage of left-handers, while the more violent societies had many more left-handed survivors.

The findings suggest that left-handers are more successful in hand-to-hand combat or fighting situations. And, indeed, this benefit may outweigh the cost of the stress that creates left-handedness. Although the research was conducted among tribes in “traditional” societies, similar results can be observed in Western society. Confrontational sports such as boxing or fencing, for example, have seen more than their fair share of successful southpaws. By the way – the word “southpaw”? It comes from baseball, where, once again, lefties often have an advantage. Since baseball diamonds are designed so that batters face east, away from the sun, a pitcher’s left hand – or paw – faces south.

That’s this week’s Note on Emerging Science, I’m Jenn Goodman.

CURWOOD: And you’re listening to Living on Earth.

[MUSIC: Tift Merritt “I’ll Be Home for Christmas” A VERY SPECIAL ACOUSTIC CHRISTMAS (Lost Highway – 2003)]