Jan. 9 (UPI) -- New research suggests women are more resilient than men.
Analysis of three centuries of historical data showed women are more likely than men to survive famines and epidemics. Their advantage is earned early. Female newborns were more likely to survive trying circumstances during the last three centuries.
Researchers say the life expectancy gender gap is at least partially explained by biological differences, as behavioral differences between male and female newborns are minimal. Scientists think genetic and hormonal differences may play a role, as previous studies have shown estrogen to help the immune system fend off disease.
Scientists at Duke University set out to measure the impact of famine, disease and other hardships on mortality rates among human populations over the last 250 years. Their datasets featured a diversity of populations, including working and former slaves in Trinidad and the United States. The data also included victims of famine in Ireland, Sweden and Ukraine during the 18th, 19th and 20th centuries, as well as the casualties of measles epidemics in 1846 and 1882 in Iceland.
The highest mortality rates were measured in Liberia, where nearly 40 percent of the freed American slaves who relocated to the African country became infected and killed by tropical diseases. Few newborns lived past age two.
Scientists found women were more resilient and lived longer overall -- even during good times. When life expectancy increased, women still outlived men by an average of between six months and four years.
The gap was most pronounced during hard times, however. When famine hit Ukraine in 1933, young females lived 50 percent longer than males.
Researchers published their findings in the journal PNAS.
"Our results add another piece to the puzzle of gender differences in survival," the scientists wrote.