SYDNEY • Australian researchers have identified 48 new genetic variants that influence if a person will be left-or right-handed, or ambidextrous, in the largest-ever study of its kind.

But scientists remained convinced that environmental factors play a larger role than genetics in terms of influence on handedness.

The study, released yesterday, analysed genetic data from more than 1.7 million people, identifying 41 genetic variants associated with being left-handed, and seven with being ambidextrous.

Coming from such a large data set, the results also reaffirmed the relatively small role that genetics plays in the process, said joint-senior author, Professor David Evans from The University of Queensland Diamantina Institute.

"The results from our analyses suggested that genetic factors could only account for a small amount of the variation in handedness, whereas environmental factors were likely to play a much more important role," he said.

"This percentage was similar for ambidexterity, meaning factors such as injuring a hand or training by playing sport or musical instruments are likely to have a strong role in a person's ability to use both hands equally well."

Study co-lead author and head of QIMR Berghofer's Psychiatric Genetics Group, Professor Sarah Medland said the causes behind left-and right-handedness go beyond just idle curiosity. "Although there is an enduring fascination with why some people are left-or right-handed or both, understanding why... is also an important research question because handedness can influence brain structure and the way different functions are located within the brain," she said.

Hand preference is first observed while still in the womb, with embryos showing single arm movements, the researchers say.

The rate of left-handedness differs across countries, from about 3 per cent to 12 per cent. In Australia, Britain and the United States, the figure is around 10 per cent.

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