Scientists have discovered another reason why women generally live longer than men. They found that lowered birth rates over the last couple of centuries has given females a biological advantage over males.
Women Benefited From Birthing Trends
In a study published by Science Daily, researchers at Uppsala University examined the demographic records of more than 140,000 individuals in Utah. After sifting through the state's population database, they concluded that female life expectancy greatly benefited from the demographic transition to low fertility and mortality rates.
The researchers found that men who were born from 1800 to 1850 lived two years longer than women. During this 50-year period, women gave birth to an average of 8 children. In the early 1900s, the figure lowered to 4 children per woman. It was during this time when females began outliving males by an average of four years.
"This illustrates the importance of considering biological factors when elucidating the causes of shifting mortality patterns in human populations," said postdoctoral researcher Elisabeth Bolund. "The results suggest that as more and more countries throughout the world go through the demographic transition, the overall sex differences in lifespan may increase."
Male Life Expectancy Was Left In The Dust
Bolund and company used the Life-History Theory to explain their findings. The theory states that each individual has limited resources that can be either put into reproduction or repair of the body.
The demographic transition to lowered birth rates meant that women have more to invest on self-preservation. Due to the reduced reproduction, the life expectancy of women skyrocketed while the life expectancy of men remained the same.
Scientific American mentioned that women tend to live longer than men since they usually have fewer bad habits. Moreover, estrogen is known to facilitate the elimination of bad cholesterol in the body while testosterone is associated to impulsiveness and violence.
