Left-handedness
© QIMR Berghofer
The study is one of the largest investigations of its kind.
About 10 per cent of Australians are left-handed and genetic analysis of more than 1.7 million people has brought scientists a step closer to understanding why.

Researchers from QIMR Berghofer Medical Research Institute and the University of Queensland have identified 48 genetic variants that influence if a person is left-handed, right-handed or ambidextrous.

Forty-one variants were linked to left-handedness and seven were associated with ambidexterity.

"Handedness is one of those things where both genetics and environment play a large role and what we've been able to do is advance the knowledge quite a bit further in the genetics side," Professor Sarah Medland from QIMR Berghofer's Psychiatric Genetics Group said.

"Each of these [variants] are just little changes in the DNA — each of them individually have very, very small effects — but when you consider all the effects together, they start to add up."

Researchers tapped into international biobanks to analyse genetic data from more than 1.7 million samples, making it one of the largest investigations of its kind.

The findings were published in the journal Nature Human Behaviour.

Professor Medland said environmental factors play a larger role than genes in determining which hand a person favours.

"Something like height is much more strongly genetically-influenced, whereas [for] something like handedness the genetic influences are relatively weak," she said.
"Through training or just through interacting with the environment and using tools that are designed one way or the other, you can actually influence someone's handedness quite a lot."
Professor Medland said the research also dispelled the belief that ambidextrousness was a middle-zone between left and right-handedness.

"The results from our study shows there was not very much genetic overlap actually between left-handedness and ambidextrousness — it seems like there are different mechanisms going on there," she said.

She said more research was needed to help answer why people developed a dominant hand.

"The reason why we do this work is to help us understand ourselves as humans and this characteristic of ourselves," Professor Medland said.

"Although we've found 41 variants influencing left-handedness and seven influencing ambidextrousness, there's a lot more out there to find."