Tongue rolling is a common physical phenomenon where an individual can manipulate the tongue into a tube or trough shape. This ability, often treated as a simple parlor trick, has long been a subject of interest in biology classrooms and among the general public. The mechanics behind the movement represent a complex feat of muscular coordination and fine motor control. The phenomenon also carries a surprising scientific history, challenging long-held assumptions about how human physical traits are determined.
The Mechanics of Rolling
The ability to roll the tongue into a tube depends on a precise, coordinated contraction of the four paired intrinsic muscles, which are located within the tongue structure. These muscles are responsible for changing the tongue’s shape rather than its position in the mouth. The lateral edges of the tongue curl upward when the superior longitudinal muscle shortens and contracts.
This shortening action is counterbalanced by the transverse muscle, which compresses the tongue horizontally to create the characteristic trough or U-shape. The fine motor control required to maintain this tubular form involves a delicate balance between these opposing muscular forces. The process is a sophisticated neuromuscular action that requires the brain to send controlled signals to the hypoglossal nerve, which innervates these muscles.
Dispelling the Simple Genetic Myth
For decades, the ability to roll one’s tongue was widely taught in introductory biology classes as a textbook example of a simple Mendelian trait. This idea suggested that the trait was controlled by a single, dominant gene, meaning that if a person inherited just one copy of the “rolling” gene, they would have the ability. The myth gained traction following a 1940 study by geneticist Alfred Sturtevant, who proposed that heredity played a role.
However, subsequent research quickly questioned this straightforward genetic model. A 1952 study involving identical twins demonstrated the flaw in the single-gene theory by finding instances where one twin could roll their tongue and the other could not. Since identical twins share nearly 100% of their DNA, this discordance proved that the ability could not be solely determined by a single gene. Sturtevant himself later acknowledged his initial assessment was likely incorrect.
Modern genetic analysis confirms the complexity of the trait, suggesting that tongue rolling is polygenic, meaning it is influenced by multiple genes. Large-scale studies have identified thousands of genetic markers that contribute to the ability, rather than a single dominant factor. This complexity means that while genetics may influence the underlying muscle structure or motor control capabilities, it is far from the sole determinant of whether a person can perform the roll.
Acquired Skill and Global Prevalence
The prevalence of tongue rolling in the human population is quite high, with various studies estimating that between 65% and 81% of people can successfully perform the action. This high percentage hints that the trait is not a rare genetic anomaly but a broadly distributed physical capability. The fact that the ability is not purely genetic suggests that environmental factors, particularly practice, play a significant role in its expression.
The ability to roll the tongue is often an acquired skill developed through maturation and motor learning. A study of Japanese schoolchildren, for instance, found that the proportion of rollers increased from 54% in younger children to 76% by age twelve, suggesting that a quarter of the group learned the skill over time. This learning process, similar to developing a new motor skill, allows individuals to gain the necessary neuromuscular coordination to control the intrinsic tongue muscles effectively. Therefore, for many individuals, the ability is not something they are born with, but rather a capacity they develop.