Girls, girls, girls!: Recent studies have shown that more girls than boys are born during times of stress. The skewed gender ratio of births following the huge 2011 Japan earthquake and subsequent tsunami adds further evidence.Courtesy Sprengben [why not get a friend]A new study shows that more girls than boys were born in the months following Japan's massive earthquake in 2011. Normally, natural gender selection is pretty much 50-50, as would be expected. But after the huge 9.0 magnitude earthquake struck off the coast of Japan, Ralph Catalano and his colleagues compared 5 years of hospital records, and found that about 2.2 percent fewer boys were born than during other times. Catalano, professor of public health at the University of California in Berkeley, thinks the reason might be for evolutionary reasons, and that hormones and more chances of miscarriages with male fetuses increase the likelihood of a female being born during times of high stress. It's not the first time the gender imbalance has been noticed. Earlier studies (in which Catalano was also involved) have shown that after the 9/11 attacks, more male fetuses didn't make it to term, and fewer male births followed the stock market crash of 2008. The latest study appeared in a recent issue of the American Journal of Human Biology.

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New Scientist story