Genes are linked to handedness

A genetic study - carried out by scientists at the Universities of Oxford, St Andrews and Bristol and the Max Plank Institute for Psycholinguistics - has identified a biological process that influences whether we are right- or left-handed. The research has been published in the journal PLOS Genetics.

Humans are the only species to show a strong bias in handedness, with around 90% of people being right-handed. The researchers were interested in understanding the genetic basis of handedness, as this could “help explain why this [right-handed] bias exists and may offer clues into the evolution of handedness and brain asymmetry”, they said.

The team carried out a genome-wide association study to identify any common gene variants that might correlate with which hand people prefer using. The most strongly associated variant was found in the gene PCSK6, which is involved in the early establishment of left and right in the growing embryo.

As first author and PhD student William Brandler explained, “The genes are involved in the biological process through which an early embryo moves on from being a round ball of cells and becomes a growing organism, with an established left and right side.” The researchers thus suggest that the genes may also help establish left-right differences in the brain, which in turn influences handedness.

Previous studies in mice showed that disrupting PCSK6 caused ‘left-right asymmetry’ defects, such as abnormal positioning of organs in the body. Meanwhile, variants in other genes known to cause left-right defects when disrupted in mice were also likely to be associated with relative hand skill.

“We propose that handedness is under the control of many variants, some of which are in genes that also contribute to the determination of body LR asymmetry,” the researchers said. Brandler said these variants include “a mixture of genes, environment and cultural pressure to conform to right-handedness”.

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