Women have an average life expectancy that’s about four years longer than men’s – regardless of culture or geography. Even among animal species, females outlive males.
Why females have an advantage in the longevity department hadn’t been well understood. In the past, some had assumed it had to do with lifestyle. However, scientists say there may be a genetic mechanism underlying this age-old phenomenon.
In a new study, researchers found that mice with two X chromosomes lived longer, regardless of other biological factors. Researchers say the finding suggests the second X chromosome may govern longevity and explain why women outlive men.
To investigate the link between chromosomes and survival, researchers tested different chromosome and gonad combinations among genetically identical mice. Some mice had biological male or female combinations mirroring those found in nature — XX with ovaries and XY with testes. Other mice had XX chromosomes paired with testes and XY chromosomes paired with ovaries.
Researchers found that mice with natural female mouse biology — two X-chromosomes and ovaries — outlived all the mice. However, mice with two X-chromosomes tended to live longer, regardless of whether they had ovaries or testes.
Among this group of mice, the longevity effect was observed beginning at 21 months, which is at the end of an average mouse lifespan. Researchers say the results point to a potential role of the second X chromosome in longer lifespans.
