Despite What You Learned in School, Tongue Rolling Isn't Simple Genetics

Remember learning genetics in science class? You heard the story of good ol' Gregor Mendel and his peas, and maybe you compared yourself to your classmates to see who had simple genetic traits like a hitchhiker's thumb or a widow's peak. Those are traits that rely on one gene variation, which makes them perfect for learning about genetics. If your science class included the ability to roll your tongue in that list of Mendelian traits, we have some bad news: Tongue rolling isn't a simple matter of genetics. You could probably even learn to do it, if you tried.

Let the Good Times Roll

Between 65 and 81 percent of people can roll their tongues in a sort of taco shape. In 1940, genetics pioneer Alfred Sturtevant published a study suggesting that tongue rolling, or "the ability to turn up the lateral edges of the tongue," as Sturtevant put it, might come down to a single dominant gene.

But even in that study, evidence against that idea was mounting. Several of the children in the study couldn't roll their tongues at first but later learned to do so. In 1951, geneticist Taku Komai noted that while only 54 percent of Japanese schoolchildren could roll their tongues at age six, 76 percent could do so at age 12. That meant that more than 20 percent of kids might learn to tongue-roll in grade school, and that's a big strike against the idea that the skill is purely genetic.

Blue Genes

Soon after, scientists started checking for the trait in every researcher's favorite natural genetics lab: identical twins. Since identical twins have identical DNA, they're a popular subject for studies examining the role genetics plays in everything from intelligence to sexual orientation. Identical twins and astronauts Scott and Mark Kelly even participated in a NASA study to find out what happens to the human body in space.

In the case of tongue rolling, even with identical genes, identical twins didn't all share the skill. That shows that while tongue rolling probably has some genetic component, it's not as simple as science class made it out to be. When it comes to learning genetics, stick to attached earlobes and chin clefts. Tongue rolling is a skill all its own.

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Learn all the things your genes can — and can't — do in "She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity" by Carl Zimmer. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer December 6, 2017

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