A school census has found that Chinese students are much less likely than others to be left-handed - but it may be due to culture, not genes.
Only 7 per cent of the 1480 Chinese students who took part in this year's Census At School, but 10 to 12 per cent of all other ethnic groups in the survey of 23,000 children, said they were left-handed.
But Ethan Chen and Aiden Warren, two left-handers in Year 9 at Mission Heights Junior College, reckon they know why so few Chinese admitted to it.
"It's possibly just in history, how some ethnic groups rejected it and some accepted it," says Ethan, an NZ-born Chinese student whose Kiwi teachers have always "supported me to be left-handed".
"The Chinese ethnic group just rejected the fact that people were born left-handed and might have forced children to grow up as right-handed," he says.
Aiden, who is of Māori and Cook Islands heritage, was told to stop using his left hand in his early schooling in Australia.
"In Australia I was always told to write with my right hand. My teacher would make me write lines with my right hand," he says.
"But it never really stuck with me. I would get in trouble and have to write more lines."
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Auckland University Emeritus Professor Michael Corballis , a world expert on handedness and brain asymmetry, says the two boys' hunch is backed by the scientific evidence.
"I think it's cultural. Some cultures are really quite severe on left-handedness," he says.
"There was quite a strong thing against left-handedness in our own culture. In the course of the last century, the reported incidence of left-handedness rose from about 2 or 3 per cent early in the century to 11 or 12 per cent."
Corballis says the evidence points to a possibility that three-quarters of all human populations are genetically hardwired to be right-handed and one quarter don't have that "handedness" gene. About half of that quarter (12 per cent) end up being left-handed.
"Even chimpanzees are 70 per cent right-handed," he says.
He says everyone receives genetic imprints from their mother and father. If handedness is like heads and tails and you need two heads to be "non-right-handed", then a quarter of us will inherit the non-right-handed imprint.
"There is an evolutionary compromise," he suggests.
"In a way, to not be handed is an advantage for lots of things, like many ball sports, and fighting perhaps.
"Against that, there are some advantages in being unbalanced and having specialisation in one side of the brain versus the other - in manipulating things like writing and using tools. So I think there was a bit of a trade-off in evolution."
Less surprisingly, the Census At School also found ethnic variations in eye colour, with Europeans far more likely than all others to have blue eyes. Corballis says blue eyes are an adaptation to colder climates and are more common the further north you go in Europe.
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