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People with slender face more likely to be left-handed

People who have a slender lower face are about 25 per cent more likely to be left-handed, a new study…

People with slender face more likely to be left-handed

(Getty Images)

People who have a slender lower face are about 25 per cent more likely to be left-handed, a new study has found.

The finding may shed new light on the origins of left- handedness, as slender jaws have also been associated with susceptibility to tuberculosis (TB), researchers said.

Slender jaws are a common facial feature, affecting about one in five US adolescents. Past surveys measured the prevalence of this condition by evaluating how the upper and lower teeth come together.

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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!" said Philippe Hujoel, professor at the University of Washington.

"Twentieth-century studies confirmed his clinical observations, as slender facial features became recognised as one aspect of a slender physique of a TB-susceptible person," said Hujoel.

"The low body weight of this slender physique is still today recognised by the Centres for Disease Control and Prevention as a marker for TB susceptibility," he said.

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.

Other populations, such as the Eskimos, were in the 19th century described as tuberculosis-resistant, having robust facial features, and typically depicted in art as showing right-hand dominance with tools and instruments.

Whether this is more than a coincidence needs further exploration, Hujoel said.

In the early 20th century, slender individuals were described as "ectomorphs" – a term that persists in popular culture as a reference to dieting and bodybuilding, Hujoel said.

"Popular websites suggest they commonly express a desire to gain weight or muscle mass. Their slightly increased chance of being a 'leftie' is an additional feature that makes them different," he added.

The study was published in the journal Laterality: Asymmetries of Body, Brain and Cognition.

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