Snails may show why lefties have an edge

Scientists speculate that they’re tougher prey for right-handed predators

Pat Wellenbach / AP file

A small garden snail peers over the edge of foliage on a flower as it tours a garden in Robinhood, Maine.

updated 11:03 p.m. ET March 23, 2006

NEW HAVEN, Conn. - Left-handed snails are better than righties at defending against predators, according to a new study that suggests lefties have the same competitive advantage in nature that they enjoy on the baseball diamond or in the boxing ring.

The study, published in this month's Royal Society Biology Letters, suggests that snails whose shells coil toward the left were more likely to survive crab attacks than those whose shells coil toward the right.

"It's just a frequency issue," said Yale geologist Gregory P. Dietl, one of the study's authors. "As long as you're rare, you're going to have an advantage."

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The researchers studied about 1,800 snail fossils, looking for scarring evidence of a predator attack. Scarring was found more frequently on right-handed snails, the study said.

Researchers offered two explanations for the advantage. Because most crabs are right-handed, they said, cracking into a shell that opens on the opposite side might be more difficult.

Alternatively, researchers said crabs might simply not be used to attacking lefties, just as baseball pitchers face fewer left-handed batters.

"It's the same thing here in nature," Dietl said. "These snails that are left-handed, they have an advantage. It doesn't become an advantage if lefties are just as common as righties."