In a study published on September 5, in the journal Brain, the team found that the set of instructions wired into the human DNA cause people to be left-handed and seem to be heavily involved in the structure and function of parts of the brain involved in language.
Previous studies have revealed that heredity has a role to play in determining left-handedness.
Experts in the cognitive sciences also established the existence of a hypothetical ‘language faculty’ which could be dominant in the left or right hemisphere depending on a person’s handedness.
However, none has been able to clarify the speculations as regards why many left-handed people reported language processing which has been linked to better verbal skills.
The scientists analysed the gene profile of about 400,000 people from UK Biobank, including 38,332 left-handers, in their attempt to spot differences and to find regions of their DNA that influenced left-handedness. Their full genetic code sequence was recorded.
They found that people with genes linked with left-handedness had better coordination in areas of the brain that deal with language.
“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,” said Akira Wiberg, a medical research council fellow at the University of Oxford.
“This raises the intriguing possibility for future research that left-handers might have an advantage when it comes to performing verbal tasks.”
According to the researchers, the differences that eventually account for this are put in place during the brain’s biological development.
“Many animals show left-right asymmetry in their development, such as snail shells coiling to the left or right, and this is driven by genes for cell scaffolding, what we call the ‘cytoskeleton’,” said Gwenaëlle Douaud, professor and senior author on the study.
“For the first time in humans, we have been able to establish that these handedness-associated cytoskeletal differences are actually visible in the brain.
“We know from other animals, such as snails and frogs, that these effects are caused by very early genetically-guided events, so this raises the tantalizing possibility that the hallmarks of the future development of handedness start appearing in the brain in the womb.”
Although they linked the genetic regions involved in left-handedness to lower chances of having Parkinson’s disease and slightly higher chance schizophrenia, the scientists added that a further study on these genetic links would offer new insights on how these conditions develop.