But she's wrong. All the biology teachers are wrong, too.

The first clue turns up on a rap sheet kept by Genome Research. A short synopsis of tongue-rolling research is followed by the trait's inheritability status:

And the more I root through the literature, the less secure I feel -- and not just because trait-trackers also investigate such hot items as "hand clasping," "arm folding" and "ear wax type," but because they turned up no evidence of inherited rollability.

Back in 1952 "Matlock" (scientists, like detectives, go by last name) concluded that identical twins don't always share the tongue-rolling trait. In 1975 "Martin" demonstrated that identical twins are no more likely to share tongue-rolling than are fraternal twins. In 1983 a Hungarian named Forrai found no genetic basis for tongue-curling -- or hand-clasping or arm-folding. And studying the Greeks of Thessaloniki in 1982, Cruz-Gonzalez established that while dry ear wax and attached ear lobes are recessive traits, which means you need the gene from both your parents, the genetic basis for tongue-rolling was less clear.

The happy news is that although tongue-rolling researchers have failed to exonerate your biology teacher, they have produced some very high-grade, if useless, trivia: In Spain 67 percent of females can roll their tongues, compared to just 64 percent of men. But Spanish men are twice as likely to wiggle their ears (20 percent) as are women. And an Iranian researcher discovered a dearth of tongue-rollers in Northern England, which, he concludes mysteriously, "may be due to mixture with Scandinavians." And hand-clasping -- concerning which thumb ends up on top -- seems related to handedness.