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SEATTLE, USA: Researchers in the U.S. have found that genetics that shape dental and thus facial features might also increase the likelihood of specific handedness. In a recently published study, people with slender faces were found to be predominantly left- rather than right-handed.
In addition, this facial phenotype might increase susceptibility to tuberculosis (TB), one of the world’s deadliest diseases, with about one-third of the population infected globally.
The findings of the study are based on three national health surveys, with a total of 13,536 participants, that were conducted in the U.S. in the 1960s and 1970s. In a review of these, researchers at the University of Washington School of Dentistry found that bilateral retrognathism—the dental marker for a convex facial profile, slender jaws and overbite—was associated with 25 percent increased odds for left-handedness in the study population. They further stated that prevalence of bilateral retrognathism in all three surveys was significantly higher among European Americans than African-Americans.
Slender jaws have also been associated with susceptibility to TB in the past. “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!” said study author Prof. Philippe Hujoel, from the university’s School of Dentistry. “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.”
According to the researchers, it is unlikely that this association was spurious. They further stated that, for example, the U.K. was described as the TB capital of Western Europe and has a high prevalence of left-handedness and people with slender faces. Populations such as the Eskimos were described as TB-resistant in the 19th century, having robust facial features and typically depicted in art as showing right-hand dominance with tools and instruments.
However, the link between facial phenotypes, handedness and TB needs further exploration, Hujoel said.
The study, titled “Handedness and lower face variability: Findings in three national surveys,” was published online on April 26 in the Laterality: Asymmetries of Body, Brain and Cognition journal.