THE reason women live roughly four years longer than men in Australia is not solely down to their reduced rate of obesity, risky behaviour and smoking. According to research published today, it's down to genetics.
Both men and women have mitochondrial DNA but researchers from Monash University in Melbourne and Lancaster University in Britain found only females were immune to mutations carried in the mitochondria, which is found in every cell of the body.
This ''evolutionary quirk'' means males are more susceptible to the mutations, negatively affecting their life expectancy.
''A significant genetic difference in lifespan between men and women can be traced back to the mitochondria,'' said the Monash University evolutionary biologist Damian Dowling.
''This difference is not caused by hormonal differences between the sexes, such as testosterone in males, or to risk-taking behaviour. It's genetic.''
The Bureau of Statistics says a girl born today can expect to live to almost 84 while a boy is expected to live to 80.
Mitochondria are found around the nucleus of cells. Often described as the powerhouse of cells because of their responsibility for producing energy, mitochondria have also been tied to the ageing process.
While both sexes have mitochondrial DNA, only the mother passes it on to her children.
''It's this strict maternal inheritance of mitochondria that has allowed mutations to creep in to mitochondrial genes that are harmful to males, while having no simultaneous effect on females,'' Dr Dowling said.
Published in Current Biology, the study took into account the tendency for men to lead riskier lifestyles than women.
''When we take out those factors, there are genetic mutations which are tied to early male ageing and these same mutations have no effect on females.''