Science has identified a trend in Canberra, Australia’s capital city, which defies the rest of the developed world — proportionally, more boys than girls are being born there.
In most states in Australia around 105 boys will be born for every 100 girls. This is seen as equilibrium because boys have a higher mortality.
But in the Australian Capital Territory there are around 110 boys born to every 100 girls.
This is the reason behind why Australia as a whole is bucking an international trend of a declining number of males being born compared to females.
In industrialised nations such the UK, the US and Canada fewer boys are being born.
A study at the Australian National University (ANU) also sheds new light on the theory that boys are more likely to be born to women of high wealth, suggesting that it could be expecting mothers’ psychological perception of their wealth that is the decisive factor.
“In the ACT there is frequently a higher number of boys born relative to girls compared to other states or territories,” says Alison Behie, head of ANU biological anthropology.
“Without the ACT numbers Australia would be consistent with the global trend for other industrialised countries.”
Dr Behie says the reason for the statistical anomaly in Canberra could be psychological.
“Our study looked at a range of maternal characteristics to see if any were an accurate indicator of whether mothers will give birth to boys or girls,” she says.
“We tested maternal education, age, bodyweight, income, but the only one that proved to be a reliable predictor was a measure known as ‘perceived wealth’.
“We found women who view themselves as being prosperous and wealthy are, biologically, having more boys.”
Canberra women earn the highest national average weekly salary and have higher education levels than the rest of Australia.
Dr Behie related the results to the Trivers–Willard hypothesis, a theory that good maternal conditions will result in an increase of males born.
“It’s well known that boys are more fragile, they are more likely to die in the womb or in childhood which is why it is normal to have more boys born than girls in any population,” Dr Behie says.
“Our research shows this may come from perception. Having the perception of prosperity is potentially more important than actually having the money or resources.”
The study used a data sample of 5,000 births across Australia over 12 years. The results are published in the Journal of Biosocial Science.
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