Rolling the tongue is not entirely a genetic trait, scientists say.
Everyone knows some people can roll their tongues and some can't--and that the ability is inherited from one's parents. Right? Actually, no.
It turns out that no one really knows why some of us can roll our tongues and some can't, but experts say heredity probably isn't the key.
"It’s extremely unlikely that tongue rolling is a genetic trait, since it’s a quite complex behavior, not in any way a simple trait," Dr. Khalil Iskarous, assistant professor of linguistics at the University of Southern California, told The Huffington Post in an email.
The genetic explanation for tongue rolling seems to have originated with a 1940 study by prominent American geneticist Alfred Sturtevant (1891-1970). But a 1952 study of twins disproved Sturtevant's findings. It showed that about 70 percent of identical twins share the tongue-rolling trait.
"If tongue rolling were purely genetic, identical twins would be identical. So we absolutely, positively know that tongue rolling is not a purely genetic trait," Dr. John McDonald, associate professor of biological sciences at the University of Delaware, told The Huffington Post in an email. "In reality, just about everything in human anatomy and behavior is determined by a complicated mix of multiple genes and the environment."
McDonald told PBS Newshour that genes may have some influence on the ability to tongue-roll but there is not a single gene for the ability.
What's more, McDonald said, there's some evidence that people can learn to roll their tongues. He pointed to a small study conducted by one of his students in which 10 non-tongue-rolling participants were asked to practice rolling their tongues. After a week of practice, one participant actually achieved a successful tongue roll.
"Rolling is quite interesting, since it seems to be the consequence of some interesting synergies between muscles, which we don’t understand, but it’s a consequence that does not seem to be used in any of the basic uses of the tongue in humans: swallowing, mastication, speech, suckling, and kissing," Iskarous said in the email. "So why be able to do it, when it’s not something we need, except for impressing people at parties? And how, biomechanically, do we do it? These are interesting questions!"
Previously on HuffPost Science: That Map Of Tastes On The Tongue That You Learned In School Has No Scientific Basis