On the Other Hand

Scientific American.com muses on the origins and biological underpinnings of right- or left-handedness. It seems humans are not alone in displaying some kind of "lateralization," or a preference for one hand (or sized of the body) over the other:

The presence of lateralization throughout the animal kingdom suggests some benefit from it, contend neuroscientists Giorgio Vallortigara of the University of Trieste and Lesley Rogers of the University of New England in Australia. Also, last August, in the journal Behavioral and Brain Sciences, the two presented evidence to support their idea that social constraints force individuals toward asymmetry in the same direction. They noted, for example, that baby chickens attack more readily when a threat appears on their left. And Rogers has found that chicks with more asymmetrical brains form more stable social groups: perhaps by approaching each other on the right, she hypothesizes, the chicks fight one another less and are more likely to notice predators.

I'm just trying to imagine the terrifying sight it must be when a baby chicken attacks. It's not quite up there with a mountain lion, is it? But anyway...

Lateralization seems to confer an advantage for some fish as well. In certain species, the majority tend to swim left when a predator attacks, whereas other species head right. The potential benefits of such patterns may not seem intuitive: a predator could learn that attacking a fish on one particular side is more effective. But Vallortigara and Rogers's idea fits with the conventional explanation of why fish school at all. When threatened, fish turning in the same direction have a greater chance of survival than if they scatter to become a darting swarm of head-butting fish.
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Given possible evolutionary reasons to conform to the norm, what about the lefties, the outliers, those who zig when all others zag? Safety from predators increases with group size, but so does competition, Vallortigara notes, making different behavior beneficial. Studies of left-handedness in some one-on-one sports, such as boxing, suggest the same. So relax, all you nonconformists.