Left-handed? Your Jaw Might Have Given It Away

May 12, 2017

Researchers have known for years that the shape of a person's jaw can be used to determine the likelihood of certain diseases and disorders. However, new research out of the University of Washington School of Dentistry shows that jaw shape may correlate to which hand is a person's dominant hand. The data indicate that people with slender jaws tend to be left-handed.

Researchers have identified another correlation associated with left-handedness: slender jaws.

Almost one in five of all U.S. teenagers have slender jaws, making it one of the most common facial features of this age group. Typically, individuals with slender jaws have an overbite caused by their lower jaw biting backward. This can also cause these people to have a convex facial profile. But there’s one anatomical feature that most don’t associate with the jawline at all — left handedness. In a new study, Philippe Hujoel, professor at the University of Washington School of Dentistry, describes a new relationship between slender lower jaws and left handedness.

Hujoel gathered data for the study from three national surveys that collected information from 13,536 individuals in the U.S. The findings indicated that left-handed people were more likely to have slender lower jaws compared to right-handed people. Slender jaws have previously been associated with a susceptibility to tuberculosis.

Hujoel said, “Almost 2,000 years ago a Greek physician was first to identify slender jaws as a marker for TB susceptibility, and he turned out to be right! Twentieth-century studies confirmed his clinical observations, as slender facial features became recognized as one aspect of a slender physique of a TB-susceptible person. The low body weight of this slender physique is still today recognized by the Centers for Disease Control and Prevention as a marker for TB susceptibility."

Based on the findings of this study, Hujoel hypothesized that the genes responsible for facial features and susceptibility to tuberculosis might also increase a person’s likelihood of being left-handed. He also noted that certain geographical coincidences, such as recorded high rates of tuberculosis infection, slender faces, and left-handedness in the United Kingdom. In contrast, Eskimos have historically been described as tuberculosis-resistant, with broad facial features and a greater incidence of right-handedness.