If you’re hoping to replicate the family you grew up in that was mostly girls or all boys, genetics won’t be on your side. According to a new study, the probability of you having children of the same gender is totally up to chance.
Researchers from the University of Queensland have conducted a study published in the scientific journal Proceedings of the Royal Society B. It analyzed the population of Sweden since 1932 and debunked the myth that having all boys or all girls runs in the family. It’s been found that the gender of a family’s children is essentially random.
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“We found individuals don’t have an innate tendency to have offspring of one or the other gender,” said Dr. Brendan Zietsch, researcher from UQ’s School of Psychology in a news release. “The chances are more like 51 to 49 of having a boy, but the genes of the mother and father don’t play any role. These findings have crucial implications for biological and evolutionary theories of offspring sex ratios.”
To conduct the study, researchers reviewed data from Swedish population registers that included every Swede born since 1932. In total, 3,543,243 people and their 4,753,269 children were analyzed as researchers linked all family members and tested whether the the sex of a person’s children was tied to the sex of their brother or sister’s children.
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The findings nix the often repeated idea that some families are more prone to having all boys and others typically wind up with girls.
“It was thought that rich or tall parents should have more boys and beautiful parents should have more girls,” Zietsch said. “It was also thought that parents’ hormone levels at the time of conception were important. Our results rule out all these possibilities and suggest a rethink of offspring sex ratio theory is necessary to properly understand why offspring sex ratios appear to vary, for example, across countries.”
The study comes more than a year after another one emerged from Japan in which scientists said that climate change will alter the ratio of the gender of newborns.
“For every society, for every year, the human being most likely to die [prematurely] is male infants. And that's true for every society that we have data for,” University of California, Berkeley, professor Ray Catalano told CNN at the time.
The CNN report noted that it’s not understood why this is the case. However, some scientists believe that boys are inherently weaker and more vulnerable to diseases and early death.
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