09 September 2019

Left-handed? It’s definitely in your genes and changes the way your brain works

New research has confirmed that left-handedness is linked to certain genetic features.

While researchers have always known that being right- or left-handed was determined by genetics, a new study has now identified the exact regions of the genome associated with left-handedness, according to a news report.

The study was led by researchers of the University of Oxford who linked the genetic differences with the connections between the different areas of the brain. It was published in the journal Brain and identified some of the genetic variants associated with left-handedness. This was done by analysing the genomes of around 400 000 people in the UK, of whom 38 332 were left-handed.

So, what's the difference?

Detailed brain imaging revealed differences in brain structures between left- and right-handed people, as well as the processes that lead to left-handedness.

"Around 90% of people are right-handed, and this has been the case for at least 10 000 years. Many researchers have studied the biological basis of handedness, but using large datasets from UK Biobank has allowed us to shed considerably more light on the processes leading to left-handedness,” stated Dr Akira Wiberg, a Medical Research Council fellow at the University of Oxford, who carried out the analysis.

"We discovered that, in left-handed participants, the language areas of the left and right sides of the brain communicate with each other in a more coordinated way. This raises the intriguing possibility that left-handed people might have an advantage when it comes to performing verbal tasks. It must, however, be taken into account that these differences only become apparent as averages in very large numbers of people, and that it wouldn't be true for all left-handers."

Other differences between left- and right-handed people were also revealed, showing a very slightly lower risk of Parkinson’s disease, but a slightly higher risk of schizophrenia in left-handed people. It is important to note, that this is a very small instance and cause and effect cannot be proven. Studying these genetic links could, however, open up the door to a better understanding of the development of serious medical diseases, stated the news report.

Complex interplay of genes

Professor Dominic Furniss, joint senior author on the study, from the Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Science at the University of Oxford, said: "Throughout history, left-handedness has been considered unlucky, or even malicious. Indeed, this is reflected in the words for left and right in many languages. For example, in English "right" also means correct or proper; in French "gauche" means both left and clumsy.

"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".

Image credit: iStock