A new study emerging from the University of Washington has found that people with slender faces are 25 percent more likely to be left-handed. This unexpected discovery was analysed by the means of three national surveys conducted in the United States among 13,536 individuals.
The finding may pave the way for the origins of left-handedness, as slender jaws have also been associated with susceptibility to tuberculosis (TB), researchers said.
About one in five U.S. adolescents have slender jaws. Past surveys measured the prevalence of this condition by evaluating how the upper and lower teeth come together. People with slender jaws typically have a lower jaw which bites a bit backward, giving them a convex facial profile and what is commonly called an overbite.
"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!" Philippe Hujoel, a professor at the University of Washington School of Dentistry and an adjunct professor of epidemiology at its School of Public Health said.
"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.", he added.
The association may explain curious geographical coincidences, researchers said. For example, the UK was described as the tuberculosis capital of Western Europe, and has a high prevalence of left-handedness and people with slender faces, they said.
The study was published in the journal 'Laterality: Asymmetries of Body, Brain and Cognition'.