Being left-handed could be down to differences in brain architecture, a new study has shown. Only 10% of the population are left-handed, as has been the case for thousands of years, but previous studies have struggled to identify the reasons behind this.

Using data from the UK Biobank, the genomes of 400,000 people, including 38,332 left-handers, were used to determine genetic regions characteristic of left-handed people. Of the four regions found to be associated with left-handedness, three were involved in brain development, specifically the structure of the cytoskeleton.

The cytoskeleton acts as the brain’s ‘scaffold’, supporting the cells as well as enabling intercellular transport, signalling and movement. 10,000 of the participants underwent detailed brain imaging to identify the differences in cytoskeleton structure between right-handed and left-handed people.

It was found there the differences in the cytoskeleton structure were in the white matter tract that connects the language speaking and processing regions in the brain. In left-handed participants, the language areas on left and right-hand sides of the brain were found to be more co-ordinately linked. It is therefore possible that left-handed people could find verbal tasks easier than right-handed people.

Humans are not the only animals that show left-right asymmetry in their development. Snails shells can coil either to the left or right, and studies involving frogs have shown that these effects are driven by genetic mechanisms in early development. It might be the case that being left or right-handed is determined early in the womb.

The senior author of the study, Professor Dominic Furness, said that ‘Here we have demonstrated that left-handedness is a consequence of the developmental biology of the brain, in part driven by the complex interplay of many genes. It is part of the rich tapestry of what makes us human.’

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