» RELATED: Here's why women outlive men even in the harshest conditions, study says
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.