Differences in infant mortality
The researchers subsequently broke down the results they had by age group and found that most of the females were surviving more due to differences in infant mortality.
“To find the female advantage so marked and consistent among all the populations was surprising,” lead researcher Zarulli said. “Even more surprising was to find that the biggest part of the sex difference in life expectancy during these crises was determined by striking differences in survival among infants. This is the most interesting result.”
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Specifically, newborn girls were tougher than newborn boys.
And the results showed that the female advantage could not be explained via behavioural and social differences between both sexes, such as their ability to take risks or engage in violence. But rather, the women’s ability to live longer in times of crisis was largely due to biological factors such as genetics or hormones.
As Zarulli noted, the most prominent female hormones, estrogens, protect blood vessels and defend against a range of diseases.
“Testosterone, the most prominent male hormone, increases the risk of several fatal conditions – besides being the cause of reckless behaviours, more typical of men, that increase the risk of accidental and violent deaths.”